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Article

Effects of Water, Fertilizer and Heat Coupling on Soil Hydrothermal Conditions and Yield and Quality of Annona squamosa

by
Weihua Wang
1,*,
Ting Bai
1 and
Xingwen Liu
2
1
Faculty of Modern Agricultural Engineering, Kunming University of Science and Technology, Kunming 650500, China
2
City College, Kunming University of Science and Technology, Kunming 650500, China
*
Author to whom correspondence should be addressed.
Agronomy 2024, 14(10), 2189; https://doi.org/10.3390/agronomy14102189
Submission received: 19 August 2024 / Revised: 20 September 2024 / Accepted: 21 September 2024 / Published: 24 September 2024
(This article belongs to the Special Issue Advances in Tillage Methods to Improve the Yield and Quality of Crops)
Browse Figures
Versions Notes

Abstract

:
Seasonal drought and summer soil high-temperature stress in Southern China often lead to decreased yield and quality of Annona squamosa. It is important to explore reasonable and effective water and fertilizer management measures as well as cover measures to improve the soil hydrothermal conditions in orchards to realize the increase in yield and quality of Annona squamosa. This study involved a two-year (2022–2023) field experiment in Yun County, Lincang City, Yunnan Province, using three factors and a three-level orthogonal test, resulting in nine different experimental treatments for water, fertilizer and heat. The three irrigation levels were W1 (soil moisture content of 55% of field moisture capacity), W2 (soil moisture content of 75% of field moisture capacity) and W3 (soil moisture content of 85% of field moisture capacity). The three fertilizer levels were F1 (1666 kg·hm−2), F2 (2083 kg·hm−2) and F3 (2500 kg·hm−2), and the three cover methods were A1 (no cover), A2 (fresh grass cover) and A3 (straw cover). The effects of these treatments on soil hydrothermal conditions, growth indices and fruit yield and quality of Annona s1uamosa were systematically monitored and analyzed, and the relationships between these treatments and yield and quality was analyzed based on a Mantel test. The results showed that T5 (W2F2A3) had the highest average soil moisture content over two years, followed by T7 (W3F1A3). The T7 (W3F1A3) treatment effectively reduced soil temperature by 5 °C compared to T1 (W1F1A1). T5 (W2F2A3) had the highest average yield over two years, with an increase of 33.99% compared to T1 (W1F1A1). Additionally, T5 (W2F2A3) has the highest average soluble solids, soluble sugars and vitamin C content over two years, with increases of 28.13%, 13.36% and 4.86%, respectively, compared to T1 (W1F1A1). A Pearson correlation analysis showed that there was a significant correlation between Annona squamosa growth and soil moisture content and soil temperature, and the Mantel test showed that soil hydrothermal conditions had significant influence on the growth and yield. T5 (W2F2A3) has the highest comprehensive benefit in promoting growth, increasing yield and improving quality for the plant. The effects of different irrigation quantities, fertilizer amounts and different cover measures on the coupling interaction for soil hydrothermal status in the root zone, growth, yield and quality of Annona squamosa were investigated, providing reliable theoretical support for the scientific planting model of Annona squamosa in the low-heat river valley of Yunnan Province.

1. Introduction

Annona squamosa, also known as A. squamosa, is a tropical fruit with high economic value, which is native to tropical America and is now widely cultivated in tropical regions of the world [1]. Yunnan Province is located in a low latitude region with diverse climate types, mainly a subtropical monsoon climate, and has environmental advantages such as a warm and humid climate, abundant annual precipitation and others. Among them, the low–hot river valley area, with small annual temperature differences, abundant light and heat resources and distinct dry and wet seasons, is suitable for growing fruits. The A. squamosa is not cold-tolerant and is usually grown in areas that are frost-free year round. As a result, A. squamosa has been widely introduced in this area. Currently, the widely grown varieties are Atemoya and African Pride [1].
The root system of A. squamosa is relatively shallow and easily affected by changes in the surface soil environment. It is particularly sensitive to water and temperature conditions and is susceptible to both drought and waterlogging. The low-heat river valley areas in Yunnan are facing problems such as hot climate, low soil moisture content, prominent water–heat contradictions and severe soil erosion. In addition, due to improper orchard management, factors such as excessive or insufficient irrigation, soil compaction and uneven nutrient distribution also seriously affect the growth, development, yield and quality of A. squamosa [2]. Therefore, exploring the reasonable coupling mechanisms of water, fertilizer and heat can provide a theoretical basis for increasing yield and improving the quality of A. squamosa.
Reasonable water and fertilizer management is the key factor to enhance the growth of fruit trees, and the growth, flowering and fruiting of trees cannot be separated from the interaction of water and fertilizer [3]. Because nutrients in the soil are absorbed by the fruit tree through the transport of water molecules, the absorption of nutrients is reduced when the soil water is insufficient [4]. However, excessive soil moisture can also lead to nutrient loss [5]. Excessive soil moisture content can obstruct air circulation, leading to the inability of roots to obtain sufficient oxygen. This can lead to root suffocation and root rot disease [6]. On the contrary, it will make the plant cells lose their turgor pressure, causing the leaves to wilt and affecting photosynthesis and metabolic processes [7]. The ability of plants to resist pests and diseases will continue to decline in the absence of adequate water [8]. Similarly, excessive fertilizer leads to the accumulation of salt in the soil, resulting in soil salinization. This affects the normal absorption of water and nutrients by the roots, resulting in poor plant growth [9]. It can also lead to excessive intake of certain nutrients and inhibit the absorption of other elements, resulting in a nutritional imbalance [10]. For example, Cui et al. [11] found that excessive nitrogen fertilizer application inhibits the absorption of potassium, magnesium, calcium and other elements. The lack of key nutrient elements affects the photosynthesis, respiration and metabolic activities of plants when the fertilizer application rate is too low. This results in growth obstruction [12], reduced fruit setting rate, impacts on dry matter synthesis and ultimately leads to a decline in fruit tree yield and quality [13]. Therefore, reasonable water and fertilizer management can effectively promote the growth and flowering of fruit trees, improve yield and quality, and bring better economic benefits to orchards [14]. However, the impact of water and fertilizer decisions varies in different regions and crop conditions. Therefore, whether the coupling of water and fertilizer can improve the growth and yield quality of A. squamosa in the low-heat river valley area of Yunnan remains to be studied.
Cover measures can effectively improve the original hydrothermal environment of soil [14]. Both straw cover and fresh grass cover can reduce soil temperature and provide a beneficial growth environment for trees in low-heat river valley areas. Straw cover is a method of covering residual parts of crops after harvesting, which can reduce soil water evaporation and increase the water retention capacity of the soil, thereby increasing the soil moisture content [15]. At the same time, it can also reduce soil erosion by rainwater, decrease soil nutrient leaching, and better preserve soil nutrients [16]. In addition, straw can also increase the content of organic matter in the soil during the decomposition process, providing nutrients required for plant growth [17]. Fresh grass cover refers to the planting of crops to cover the soil surface. Fresh grass cover can not only inhibit weed growth and reduce soil erosion [18], but also certain Leguminosae plants also have nitrogen fixation abilities which can convert nitrogen from the air into nitrogen fertilizer that can be used by plants, thereby improving soil nutrient status [19]. As an herbaceous plant, Trifolium repens has a short growth cycle and is easy to manage, making it an ideal choice for fresh grass cover [20]. The use of T. repens for surface cover can not only improve the soil microenvironment and reduce the occurrence of diseases and pests but also increase soil fertility and improve the content of organic matter and the number of microorganisms in the soil [21]. Feng et al. [22] and Tu et al. [23] showed that straw and fresh grass cover could significantly increase soil moisture and effectively reduce soil temperature [24,25]. However, their conclusion was based on the climate environment of the Loess Plateau. Sun et al. [26] found that fresh grass cover also helps to increase the nutrient content in soil and enhance soil enzyme activity, but it also has a competitive effect on soil water [27]. At present, research on fruit tree cover measures mainly focuses on fruits such as apples [28], pears [29] and citrus [30]. Therefore, it is still necessary to further explore whether the A. squamosa cover measures can promote the growth of fruit trees, increase fruit yield and improve fruit quality in the hot and dry valley area.
Water, fertilizer and heat are three important factors for plant growth [31]. Due to the unique climatic and geographical conditions of Yunnan province, three factors play a more prominent role in the cultivation of A. squamosa. Therefore, it is of great significance to develop a reasonable and effective water, fertilizer and heat coupling cultivation method. Based on two years of field experiment data (2022–2023), this study analyzed how different irrigation levels, fertilization rates and cover measures affected soil moisture content and soil temperature, and subsequently affected the growth, fruit yield and quality of A. squamosa. At the same time, the effects of soil hydrothermal conditions on the yield and quality of the fruit were also discussed. This study aims to provide a scientific basis for determining the most suitable water, fertilizer and heat coupling cultivation method for A. squamosa in Yunnan’s low-heat river valley area through a comprehensive analysis of the results and to provide management references for water, fertilization and covering measures for planting in orchards.

2. Materials and Methods

2.1. Overview of the Experimental Area

The experiment was conducted from March 2022 to mid-October 2023 in a five-year A. squamosa orchard (100°105 3′09″ E, 24°406′309″ N) in Yun County, Lincang City, Yunnan Province, which is located in the southwest of Yunnan Province, China, with an altitude of 1300 m and a subtropical monsoon climate (Figure 1). The annual sunshine duration is 2252.3 h, the annual average temperature is 21.2 °C, the frost-free period is 317~357 days, the average annual rainfall is 905.6 mm, and the rainfall is mainly concentrated from May to July. The changes in average daily temperature (T) and precipitation (P) during the experiment are shown in Figure 2. According to the general precipitation evaluation standard, in China, 2022 was a dry year, and 2023 was a normal year. The soil bulk density of the experimental field was 1.35 g·cm−3, the organic matter was 16.12 g·kg−1, the pH value was 6.97, the available phosphorus was 23.8 mg·kg−1, the rapidly available potassium was 405 mg·kg−1, and the soil fertility was medium. The experimental orchard covered an area of more than 33.33 hm2 and was established in 2016, with a row spacing of 3 m × 4 m, running north–south. The fruit trees in the park grew vigorously, had moderate vigor and were free of pests and diseases. The management of fruit tree growth in the area is representative.

2.2. Experiment Design

The experiment was carried out in March 2022 in an orchard with similar growth and disease-free A. squamosa trees as the experimental subjects. The field test was arranged based on a three-factor and three-level orthogonal experimental design, and the orthogonal experiment scheme is shown in Table 1. Three factors were set: irrigation levels (W), fertilizer amount (F) and root zone temperature (A). Three levels were set for each factor, and each was repeated three times. A total of 27 plots were randomly arranged. The three irrigation levels were severe deficit irrigation W1 (soil moisture content of 55% of field moisture capacity), mild deficit irrigation W2 (soil moisture content of 75% of field moisture capacity) and full irrigation W3 (soil moisture content of 85% of field moisture capacity). Soil samples were collected every 7 days to measure the soil moisture content during the experiment. The upper limit of irrigation water was the designed 3 irrigation levels, and the lower limit of irrigation water was the measured soil moisture content under each treatment. The irrigation calculation formula was as follows:
M = 10γH (θmax − θ0)
where M is the irrigation quantity (mm); γ is the soil bulk density in the planned moist layer, and the measured value is 1.3 g·cm−3; H is the thickness of the planned moist layer of soil, which is 0.8 m; θmax is the upper limit of irrigation (%); and θ0 is the soil moisture content (%) before irrigation.
The three fertilization levels were low fertilizer (F1: 1666 kg·hm−2), medium fertilizer (F2: 2083 kg·hm−2) and high fertilizer (F3: 2500 kg·hm−2). The tested fertilizer was a water-soluble compound fertilizer for fruit trees (N/P2O5/K2O was 15/15/15). The fertilizer was applied evenly into the plot according to local fertilization practices and added to the soil with irrigation. The three cover measures were A1 (no cover), A2 (fresh grass cover) and A3 (straw cover). The experiment was not covered by artificial weeding, and there were no weeds during the experiment. The fresh grass seed was T. repens, the seed amount was 50 kg·hm−2, and the straw cover was the whole stalk after corn harvest, with a covering thickness of 15 cm, evenly scattered on the ground along the contour line of the plot.
The plants in the experimental area were five-year-old trees with a row spacing of 3 m × 4 m. The growth period of the fruit trees was divided into four stages: flower bud differentiation stage (I: 15 March 15–5 May), flowering and fruiting stage (II: May 6–June 15), fruit expansion stage (III: 16 June–15 August) and maturity stage (IV: 16 August–5 October). Two drip irrigation belts were laid in parallel in each planting row, 50 cm away from the trunk, with a 4 L·h−1 drip head flow rate, 30 cm drip head spacing and 4 drip heads for each tree to implement integrated irrigation of water and fertilizer (Figure 3). The three trees with good growth were selected for sampling from 4 fruit trees in each test area. The other agronomic management measures were consistent in all experimental areas except for the experimental treatment.

2.3. Measurments

Soil Parameters: soil moisture content, soil temperature.
Growth index: new shoot length, new shoot diameter, leaf area index (LAI).
Yield: single fruit weight, total yield.
Quality: titratable acidity, total soluble solids, sugar–acid, soluble sugar, vitamin C.

2.4. Methods

The soil moisture content was determined based on mass moisture content. Three fruit trees with good growth were selected in every experimental zone at each growth stage of the fruit trees (flower bud differentiation stage, flowering and fruit setting stage, fruit expansion stage and maturity stage), and random samples were taken at 25 cm between the fruit trees and the drip irrigation belt. The soil moisture content of the 0–40 cm soil layer was measured using the drying method, with each layer being 10 cm.
The soil temperature was measured using a right-angle ground thermometer. A set of ground thermometers was buried near the uniform growth of fruit trees in each experimental area for fixed-point measurement, and the buried depths were 5, 10, 15, 20 and 25 cm, respectively. The ground temperature was read at 8:00, 12:00 and 18:00 on the first clear day after irrigation during the test period, and the average temperature of the three periods was calculated during the analysis. The ground temperature was measured at a fixed position in each growth period.
Growth index: The length of new shoot growth throughout the tree in a year is one indicator of the strength of the tree. Leaf area is the total area of a crop’s leaves and is an important basis for crop photosynthesis [32]. When the tree began to grow new shoots, the length reached about 10 cm, and the new shoots were measured in each direction to the east, south, west and north. The length and diameter of new shoots were measured every 10 days using a soft tape measure and vernier caliper until the new shoots stopped growing. A canopy analysis system (Sunscan) was used to measure the leaf area index (LAI) [33] every 10 days from the beginning of the leaf growth period until the end of the growth period.
Yield: Individual fruit quality is an important indicator for assessing the market value of fruit [34]. The yield of three fruit trees under each treatment was measured after the fruit matured. Three fruits were selected from the east, south, west and north of the tree, and the single fruit weight was measured using a balance with an accuracy of 0.01 g and a maximum measurable mass of 1000 g. The total fruit yield of three trees in each treatment group was measured at the fruit maturity stage, and the hectare yield was converted according to the measured yield.
Quality: After the fruit was picked and placed at room temperature for soft maturity, various quality indicators were measured. Titratable acidity and total soluble solids were determined using conventional methods [35]. Sugar–acid was the total soluble solids to ratio of titratable acidity. The content of soluble sugar was determined using the spectrophotometric method [36]. The vitamin C content was determined using spectrophotometry [37]. The ratio of sugar to acid was the ratio of soluble sugar to organic acid.

3. Statistical Analysis

The data and charts were processed using Excel, SPSS23.0, MATLAB 2018, and Origin 2021 software.

4. Results

4.1. Effects of Water, Fertilizer and Heat Coupling on Soil Hydrothermal Properties

4.1.1. Effects of Different Treatments on Soil Moisture Content

The two-year data showed that irrigation had significant effects on the moisture content of A. squamosa throughout the whole growth period. The amount of fertilizer applied had a significant effect on the flowering and fruiting period in 2022. The effects of cover measures on the whole growth stage in 2022, flower bud differentiation stage, flowering and fruiting stage and fruit expansion stage in 2023 were significant (p < 0.05) (Figure 4). During the whole growth period of the plant in 2022 and 2023, the soil moisture content in the 0–40 cm soil layer decreased with the depth of the soil layer. The soil moisture content was the highest in the 0–10 cm soil layer, and the decrease was the largest in the 20–30 cm soil layer. The average soil moisture content in each growth stage in 2023 was higher than that in 2022 because of the different rainfall and temperature between the two years.
The average soil moisture content of the T5 (W2F2A3) treatment in the 0–40 cm soil layer was the highest during the flower bud differentiation stage and flowering and fruit setting stage in 2022 and 2023, which were 20% and 16.42% (2022) and 25.76% and 21.626% (2023), respectively. Compared with the T1 (W1F1A1) treatment, it increased by 27.03% and 31.23% (2022) and 22.73% and 24.18% (2023), respectively. The average soil moisture content of the T9 (W3F3A3) treatment in the 0–40 cm soil layer was highest during the expanding and ripening stages of the fruit in 2022, which was 44.39% and 40.33% higher than that under the T1 (W1F1A1) treatment, respectively. The average soil moisture content of the T4 (W2F1A2) treatment in the 0–40 cm soil layer was highest during the fruit expanding stages in 2023, with an increase of 25.21% compared to T1 (W1F1A1). The average soil moisture content of T7 (W3F1A3) in the 0–40 cm soil layer was highest during the fruit maturity stage in 2023, with an increase of 23.71% compared to T1 (W1F1A1).
The average soil moisture content of T7 (W3F1A3) in the 0–40 cm soil layer during the entire growth period was highest in 2022, which was 16.38% and 0.08% higher than T3 (W1F3A3) and T5 (W2F2A3) under the same cover measures of A3, respectively, and 16.43% and 0.48% higher than T8 (W3F2A1) and T9 (W3F3A2) under the same irrigation quantity of W3. The average soil moisture content of T4 (W2F1A2) in the 0–40 cm soil layer during the entire growth period was highest in 2023, which was 11.53% and 1.93% higher than T2 (W1F2A2) and T9 (W3F3A2) under the same cover measure A2, compared with T5 (W2F2A3) and T6 (W2F3A1) under the same irrigation quantity W2, with an increase of 0.76% and 10.64%, respectively. T5 (W2F2A3) had the highest average soil moisture content in the 0–40 cm soil layer during the whole growth period of two years, which was 24.96% higher than T1 (W1F1A1).

4.1.2. Effects of Different Treatments on Soil Temperature

The two-year data showed that irrigation quantity and cover measures had significant effects on soil temperature from 0 to 25 cm during the whole growth period of A. squamosa (p < 0.05), and the influence of irrigation quantity on soil temperature was greater than that of cover measures (Figure 5). The soil temperature at 5 cm was greatly affected by weather, and the soil temperature decreased with the increases in soil depth. The average soil temperature in 2022 was generally lower than that in 2023, affected by the weather. In the low temperature and during the stage of plant flower bud differentiation in two years, the change in average soil temperature in the 0~25 cm soil layer of cover measures A3 and A2 was smaller than that of A1, with a decrease of 0.6~1.8 °C. The average soil temperature decreased with the increase in irrigation quantity, and the largest decrease occurred between W1 and W2, with a decrease of 1.6~1.9 °C. In the flowering, fruiting and expanding stage of the fruit, the average soil temperature of the 0–25 cm soil layer was consistent with the atmospheric temperature. The highest soil temperature in two years was T1 (W1F1A1), and the average temperature in the T1 (W1F1A1) treatment in both two years was 5.9 °C higher than that in the T7 (W3F1A3) treatment. At the fruit maturity stage, the effects of irrigation quantity and cover measures on soil temperature were reduced. The average temperature of W2 was 1.5 °C lower than W1 both in two years, and the average temperatures of cover measures A3 and A2 were 1.7 °C and 1.2 °C lower than A1 in both years.
The growth period average highest soil temperature in the 5 cm soil layer during the two years was treated with T1 (W1F1A1), and the lowest soil temperature was treated with T7 (W3F1A3). The average soil temperature in the 5 cm soil layer of T7 (W3F1A3) was significantly reduced by 5.6 °C over two years compared to T1 (W1F1A1). Compared with T3 (W1F3A3) and T5 (W2F2A3) under the same cover measure A3, the average soil temperature was reduced by 3.4 °C and 1.2 °C over two years, respectively. Compared with T8 (W3F2A1) and T9 (W3F3A3), under the same irrigation quantity W3, the average soil temperature was reduced by 1.9 °C and 0.5 °C over two years, respectively. The changes in soil temperature in the 10 cm, 15 cm, 20 cm and 25 cm soil layers were similar to those in 5 cm soil layer, but the average soil temperature during the two-year growth period and the difference between each treatment decreased with increasing soil depth.
Under irrigation quantity W3, cover measure A3 in 2022 and 2023 reduced the average soil temperature of the 0–25 cm soil layer of plants throughout the whole growth stage by 1.7 °C compared with A1, and A2 decreased by 1.1 °C compared with A1. Cover measure A3 under the irrigation quantity W2 decreased by 0.9 °C compared to A1 over two years, and A2 decreased by 1.6 °C compared to A1 over two year. Cover measure A3 under the irrigation quantity W1 decreased by 1.3 °C compared to A1 over two years, and A2 decreased by 0.7 °C compared to A1 over two years.

4.2. Effects of Water, Fertilizer and Heat Coupling on the Growth Indicators of A. squamosa

Table 2 shows the changes in three growth indicators of A. squamosa in 2022 and 2023 under different treatments. The new shoots length, new shoots stem diameter and the average value of leaf area index (LAI) of plants in 2022 were 80%, 87% and 85% of those in 2023, respectively. Irrigation quantity had significant effects on the new shoot length and new shoot stem diameter of fruit trees in 2022 and the two-year average value of LAI (p < 0.05), and it had extremely significant effects on the new shoot length and new shoot stem diameter of the fruit trees in 2023 (p < 0.01). The two-year average value of the new shoot length and new shoot stem diameter for irrigation quantity W3 was the highest, which increased by 14.67%, 0.09% and 8.4%, 0.44% compared with W1 and W2, respectively. W2 had the highest average value of LAI, increasing by 8.37% and 3.42% compared with W1 and W3, respectively. The fertilization amount had significant effects on the new shoot length of A. squamosa over two years (p < 0.05). The length of new shoots in 2022 increased with the increase in fertilizer amount, and the fertilizer amount of F3 was 3.04% and 2.23% higher than that of F1 and F2, respectively. The length of new shoots in 2023 increased first and then decreased with the increase in fertilizer amount, and the fertilizer amount of F2 increased by 6.27% and 1.24% compared with F1 and F3, respectively. The cover measures had an extremely significant impact on the stem diameter of new shoots in 2023 (p < 0.01). The new shoots stem diameter of cover measures A2 and A3 increased by 14.98% and 19.43% respectively, compared with A1.
The new shoot length, new shoot stem diameter and LAI under the treatment of T1 (W1F1A1) were all at the lowest level. The new shoot length of T6 (W2F3A1) was the highest, which increased by 16.24% compared with T1 (W1F1A1). The highest new shoot stem diameter and the average value of LAI were T4 (W2F1A2), which were 17.27% and 7.86% higher than T1 (W1F1A1), respectively. In 2023, the new shoot length and average value of LAI were the highest under the T5 (W2F2A3) treatment, and they increased by 26.4% and 14.53% compared with T1 (W1F1A1), respectively. The new shoot stem diameter under the T9 (W3F3A2) treatment was the highest, which was 26.47% higher than that under the T1 (W1F1A1) treatment.

4.3. Effects of Water, Fertilizer and Heat Coupling on Yield and Quality of A. squamosa

The single fruit weight and yield of A. squamosa in two years are shown in Figure 6. Single fruit weight is an important indicator for evaluating the size of fruit. Irrigation quantity and fertilization amount had significant effects on single-fruit weight in both years (p < 0.05) (Figure 6). The single-fruit weight value under the T5 (W2F2A3) treatment in 2022 and T6 (W2F3A1) treatment in 2023 was the highest, which significantly increased by 47.17% and 44.24% compared with T1 (W1F1A1), respectively. The single-fruit weight of irrigation quantity W2 in 2022 increased by 30.8% and 2.8% compared with W1 and W3, and it increased by 30.7% and 5.7% in 2023, respectively. The fruit weight in two years also increased with the increase in fertilizer amount. The single fruit weight of fertilizer amount F3 in 2022 increased by 14.07% and 1.92% compared with F1 and F2, and it increased by 14.63% and 4.88% in 2023, respectively. The single-fruit weight of cover measures A3 in 2022 increased by 8.44% and 5.58% compared with A1 and A2, and it increased by 3.67% and 4.09% in 2023, respectively.
Irrigation quantity and fertilizer amount had significant effects on the yield of fruits in two years (p < 0.05) (Figure 6). The highest yield was achieved under the T5 (W2F2A3) treatment in 2022 and under the T6 (W2F3A1) treatment in 2023, with significant increases of 33.33% and 36.25% compared to the T1 (W1F1A1) treatment, respectively. The highest fruits yield in 2022 was under W3, with an increase of 21.99% compared to W1. The highest fruits yield in 2023 was under W2, with an increase of 26.98% compared to W1. The fruit yield in 2022 increased by 9.8% and 0.68%, respectively, compared to F1 and F3 under the application of fertilizer F2. The fruit yield of fertilizer amount F3 in 2023 increased by 10.81% and 3.89%, respectively, compared to F1 and F2. The fruit yields of cover measure A3 in 2022 and 2023 were higher than that of A1 and A2. Based on the data for these two years, the single-fruit weight and yield of T5 (W2F2A3) were the highest, which increased by 44.65% and 33.99% compared with T1 (W1F1A1).
The quality of A. squamosa fruit under different treatments was compared and analyzed (Table 3). The soluble solid content of the T5 (W2F2A3) treatment was the highest in both years, which was 28.13% higher than that of T1 (W1F1A1). The cover measure A3 had the most significant impact on the content of soluble solids, which increased by 6.64% and 3.39% compared with A2 and A1, respectively. The soluble sugar content of fruits in 2022 and 2023 showed a trend of first increasing and then decreasing with the increase in irrigation amount. The average soluble sugar content of irrigation quantity W2 was 6.91% and 7.97% higher than that of W1 and W3, and the average soluble sugar content of fertilizer amount F2 was 7.69% and 6.45% higher than that of F1 and F3. Cover measure A3 had a significant effect on improving the content of soluble sugar, while there was no significant difference in the value of average soluble sugar between A2 and A1. Cover measure A3 increased the sugar content while reducing the acidity of the fruit, thereby increasing the sugar acid ratio by about 2.71% to 2.82%. The content of vitamin C showed a trend of first increasing and then decreasing with the increase of irrigation amount. The vitamin C content in 2022 and 2023 was highest under the T5 (W2F2A3) treatment, and the average increase in two years was 4.86% compared with T1 (W1F1A1).

4.4. The Correlation between Yield and Quality of A. squamosa under Water, Fertilizer and Heat Coupling

The Mantel test and correlation analysis showed that the yield and quality of A. squamosa were significantly related to soil moisture content, soil temperature and growth (Figure 7). Soil moisture content was negatively correlated with soil temperature at different growth stages. The new shoot length of the fruit trees in 2022 was positively correlated with soil moisture content at different growth stages (p < 0.05) and negatively correlated with soil temperature at different growth stages (p < 0.05). In 2023, the new shoot length and new shoot stem diameter of the fruit trees were positively correlated with the soil moisture content at the flower bud differentiation stage, flowering and fruit setting stage and maturity stage (p < 0.05), and negatively correlated with soil temperature at each growth stage (p < 0.05). LAI in 2023 was positively correlated with soil moisture content in each growth stage (p < 0.05) and negatively correlated with soil temperature in each growth stage (p < 0.05). Fruit yield in 2022 was significantly positively correlated with soil moisture content at the flowering and fruiting stage, fruit expansion stage and maturity stage, soil temperature at each growth stage and new shoots length (p < 0.05). The fruit quality index in 2022 showed a significant positive correlation with LAI (p < 0.05). In 2023 the fruit yield was significantly positively correlated with soil temperature, LAI and new shoot length and new shoot stem diameter during the whole growth stage (p < 0.05), and the quality index was significantly positively correlated with soil moisture content and LAI at the flowering and setting stage (p < 0.05). In conclusion, soil moisture content and soil temperature at each growth stage had a significant effect on the growth and yield of A. squamosa, and LAI had a significant effect on quality.

5. Discussion

5.1. Effects of Water, Fertilizer and Heat Coupling on Soil Hydrothermal Properties

The double stress of the high summer temperature and seasonal drought in South China will lead to high soil temperature and poor moisture retention, which will seriously affect the growth and development of A. squamosa. This study indicates that ground cover measures and irrigation quantity were the key factors affecting soil hydrothermal conditions. The soil water retention effect of the straw cover under the same quantity of irrigation was > fresh grass cover > no cover. This is because the straw cover can suppress soil moisture evaporation and reduce surface runoff, effectively blocking the exchange of air flow between the atmosphere and soil [38], thereby increasing the soil moisture content. Under the same cover measures, adequate irrigation will make the nutrients in the soil migrate to the deeper soil layer, while low irrigation will make a large amount of soil nutrients remain on the surface [3]. Therefore, moderate deficit irrigation and reasonable fertilization have entropy-increasing effects. In this study, under excessive deficit irrigation, the difference in soil moisture content between fresh grass cover and uncovered soil was small, which may be due to intensified water competition of fresh grass under excessive drought stress [39], but this competition would be weakened under full irrigation. Therefore, the effects of straw cover and fresh grass cover on soil moisture under full irrigation are slightly different, and the water retention capacity of the straw cover under deficit irrigation is greater than that of the grass cover. Under the combined effects of water, fertilizer and heat conditions, the research data showed that T5 (W2F2A3) was the highest soil moisture content in the whole growth period of A. squamosa in 2022 and 2023, and the soil entropy was the best under moderate deficit irrigation and straw cover treatment. The increase in temperature and water temperature in the summer will lead to the low infiltration rate of local soil, and adequate irrigation is more likely to form surface runoff and cause a large amount of water loss [40]. Therefore, reasonable water and fertilizer regulation can improve soil water storage capacity, and the coupling interaction of water and fertilizer can regulate the soil water use efficiency of crops and change the distribution of soil water [41].
Ground mulch has been widely used in crop cultivation and production, mainly including film cover and organic cover. Namaghi et al. [42] found that under high-temperature conditions in summer, plastic film coverings would cause the soil temperature to rise by 6.5 °C. Compared with no covering treatment, the rising temperature would reduce leaf nitrogen concentration and yield, so selecting a suitable ground cover method would be more conducive to crop growth. Straw covers and fresh grass covers have a physical shading effect on soil, which can effectively block solar radiation and reduce soil temperature in high summer temperatures [43]. A. squamosa is warm and afraid of sun, the appropriate temperature is conducive to the growth of it, with the most suitable temperature is 25~30 °C. In summer, due to the high amount of solar radiation, the temperature rises and the soil temperature becomes too high, which can affect the growth of A. squamosa. This study showed that the average soil temperature under straw cover and fresh grass cover in mid-summer was 1.2~3.2 °C and 0.8~2.1 °C lower than that under no cover treatment, respectively, which was consistent with the research results of Lu et al. [36]. Irrigation also affects the change in soil temperature. Soil temperature changes with the change in air temperature before irrigation, and the temperature of each soil layer gradually decreases through irrigation [44], indicating that irrigation can effectively slow down the rise of soil temperature. This study also showed that the variation range of soil temperature increased with the increase of irrigation quantity, and the cooling effect of full irrigation was greater than that of deficit irrigation. During the whole monitoring period, the dynamic changes in soil temperature in the 10–25 cm soil layer were similar to those at a depth of 5 cm, but the differences in soil temperature between the treatments decreased with increasing soil depth. The soil temperature in the 15 cm soil layer under severe deficit irrigation and fresh grass cover was the highest in the fruit expansion stage in 2022, which was different from that in the other growth stages and soil layers. This may be due to the competition between fresh grass and A. squamosa during water shortage [39], which resulted in the decrease of soil moisture in the root soil and the increase of soil temperature compared with that in the absence of cover. The influence of irrigation and cover measures on soil temperature was less than that of other growing periods during the mature stage.

5.2. Effects of Water, Fertilizer and Heat Coupling on the Growth Indicators of A. squamosa

The new shoot length, new shoot stem diameter and LAI are important indicators of the growth of A. squamosa, which can directly reflect the growth status. The growth index is an important factor affecting the yield and quality, and the new shoot length, new shoot stem diameter and LAI are also the source driving force of A. squamosa. Especially when A. squamosa enters the flower bud differentiation stage, plant transpiration and field evaporation increase with temperature increases, and reasonable water and fertilizer regulation and mulching measures can effectively improve soil hydrothermal conditions, promote dry matter accumulation and facilitate growth [45,46].
According to the data of two years, the new shoot length, new shoot stem diameter and LAI increased first and then decreased with the increase in irrigation amount. This may be because as the amount of irrigation increases, plants are better able to carry out photosynthesis and nutrient absorption [47], thereby promoting the growth of new shoots and an increase in leaf area. However, excess irrigation leads to the deterioration of soil aeration in the root zone of crops and the loss of soil nutrients [48], resulting in slow root respiration, nutrient deficiency and inhibiting the growth of crops [49], indicating that mild deficit irrigation and reasonable fertilizer application are more conducive to the growth of A. squamosa.
The new shoot length increased with the increase in fertilizer amount in 2022 but showed a trend of first increasing and then decreasing in 2023. This was attributed to the low soil fertility in 2022. Increasing fertilizer application can provide sufficient nutrients for crops, which promotes root growth and development, crop absorption of water and nutrients and the growth of new shoots [39]. The nutrient level in the soil in 2023 was improved, and the basic fertility was high through a year of fertilization treatment. Therefore, moderate fertilization can continue to promote growth, but excessive fertilization may lead to nutrient excess, which is actually detrimental to plant growth [50]. Elia et al. [51] showed that excess fertilizer application would lead to early growth of new shoots. Excessive leaf area led to a larger transpiration area and increased water consumption, which is consistent with the results in 2023 in our study. In this study, T5 (W2F2A3) had a better overall growth index, which may be due to excessive transpiration caused by excessive LAI under high water and fertilizer conditions [52]. But low water and fertilizer led to insufficient nutrients, resulting in slow crop growth [53]. Therefore, the hydrothermal conditions under the medium soil moisture and nutrient levels were better, which did not lead to the problem of premature growth and excessive growth of new shoots.
This experiment was conducted under different combinations of cover methods and water, fertilizer and heat coupling, and the coupling interaction of the multiple factors caused differences that were unique from the single water and fertilizer regulation effect. At the same time, the data also showed that both straw cover and fresh grass cover could increase the growth of A. squamosa shoots, and the straw cover effect was more significant. This was attributed to the fact that both straw cover and fresh grass cover belong to organic cover, which can improve soil structure, increase soil fertility and promote plants growth [54]. Meanwhile, Dong et al. [55] showed that higher root zone temperature would slow down the rate of alkaloid synthesis and accumulation at the root and reduce the water potential of stems and leaves, thus affecting the physiological growth of crops. This study found that both straw cover and fresh grass cover could effectively reduce the temperature in the root zone of A. squamosa, but the growth index under the straw cover was better than that under the fresh grass cover, which might be because the straw cover could reduce the heat absorption of soil surface during the day and keep the soil temperature relatively low [56], but it retained the heat in the soil at night to avoid the soil temperature becoming too low. A stable soil temperature is more conducive to the healthy growth of roots and nutrient absorption. Fresh grass covering also has a certain effect on soil temperature regulation, but because fresh grass growth is affected by season and climate, its cover effect is not as durable and stable as straw. Therefore, straw cover was better than fresh grass cover for the growth of A. squamosa.

5.3. Effects of Water, Fertilizer and Heat Coupling on Yield and Quality of A. squamosa

Yield and quality are decisive factors in measuring fruit [57], and appropriate cultivation techniques are the key to increasing yield and improving quality. In this study, the single fruit weight and yield were highest under the T5 (W2F2A3) treatment in 2022, with an increase of 47.17% and 33.33% compared to T1 (W1F1A1). The T6 (W2F3A1) treatment resulted in the highest single-fruit weight and yield in 2023, with an increase of 44.24% and 36.25% compared to T1 (W1F1A1). This may be because the soil moisture content of the root system changes due to the coupling interaction of water, fertilizer and heat, effectively improving the soil structure and nutrients [58], promoting root growth and enabling the fruit tree to better absorb water and nutrients. The study by Perez Pastor et al. [59] showed that excessive growth of new shoots in fruit trees can be avoided under a mild water and fertilizer deficit, and more nutrients can be transported to reproductive organs to increasing the fruit setting rate of fruit trees. But, excessive use of fertilizers can cause problems such as soil compaction, soil pollution and other problems [60]. Straw covering can also improve soil moisture content and improve crop water and fertilizer utilization efficiency [61], which was consistent with the results of our experiment in 2022. The T6 (W2F3A1) treatment had the highest single-fruit weight and yield in 2023, which may have been due to the increase in basic fertility in the soil after one year of fertilization treatment. Although the non-covering treatment could lead to the loss of some nutrients, due to the nutrient accumulation degree being obviously greater than the loss degree under two years of high-fertilizer treatment, which provided sufficient nutrient requirements for plant growth, the difference in temperature change was 2023 is smaller than in 2022, making the impact of coverage measures less prominent than in 2022. In this study, the soil hydrothermal conditions could be adjusted under the fresh grass cover, but it was not helpful to increase the yield. This may be due to the cover’s water and fertilizer competition with A. squamosa [62], resulting in the reduction of nutrients for the growth of fruit trees and a decrease in the yield of fruits, which was consistent with the results of TerAvest et al. [63].
The content of soluble solids directly affects the taste of A. squamosa, and the content of soluble solids in the T5 (W2F2A3) treatment was the highest in both years. This may be because deficit irrigation during the fruit expansion stage can improve the soluble solids of fruits, which is consistent with the study by Zhong et al. [64]. Cover measure A3 had a significant impact on the content of soluble solids, which was because organic coverings can effectively increase the nutrient concentration of leaves, help crops perform better photosynthesis and promote the growth and development of crop vegetative organs and reproductive organs [65]. Meanwhile, as a fruit with a sweet and sour taste, the degree of sweetness and sourness is particularly important for the taste. Moderate water stress makes the internal ripening of the fruit early, increasing the accumulation of sugar [66] and relatively reducing the acidity. Two years of data show that the cover measure A3 not only reduces the acidity but also increases its sugar content, thereby increasing the sugar to acid ratio by 2.71% to 2.82% and resulting in a better taste. In this study, the content of vitamin C showed a trend of first increasing and then decreasing with the increase in irrigation quantity, which may be because appropriate irrigation can promote photosynthesis, metabolic activity and antioxidant mechanisms and increase the synthesis and accumulation of vitamin C [67]. However, excessive irrigation can lead to problems such as root hypoxia, nutrient loss and decreased photosynthetic efficiency [68], thus inhibiting vitamin C synthesis. The T5 (W2F2A3) treatment had the highest vitamin C content in 2022 and 2023, and the vitamin C content significantly increased compared to coverage measures A1 and A3.

6. Conclusions

Compared with other treatments, the T5 (W2F2A3) treatment significantly increased the soil moisture content, effectively reduced the soil temperature in midsummer and maintained the appropriate temperature for the growth of A. squamosa. The Mantel test and correlation analysis showed that soil moisture content and soil temperature had a strong correlation with the growth and yield. Suitable soil moisture is a key factor in the growth of A. squamosa. Soil moisture determines the supply of water to fruit trees and is important for fruit tree growth and development, drought monitoring and control. Soil water and heat are important conditions for A. squamosa growth, improving soil. The high soil temperatures in summer can affect A. squamosa growth, causing A. squamosa to suffer from burns and poor color. Improving soil water and heat conditions is an important measure to increase A. squamosa yields and improve quality. Effective mulching measures can improve soil hydrothermal conditions. As the amount of irrigation and fertilizer application increases, crop yields will be significantly, but there is a threshold above which crop yields decline. Too much irrigation and fertilizer application can lead to overgrowth of stems and leaves, resulting in lower yields. Too little irrigation and fertilization can lead to severe water stress and lack of nutrients for growth, resulting in reduced yields. The comprehensive yield and quality index analysis for water and fertilizer conservation showed that the application of slight deficit irrigation, moderate levels of fertilization, and straw cover were the best combination for increasing the yield and improving the quality of A. squamosa. Therefore, the selection of suitable planting patterns according to the main limiting factors in different regions can promote the sustainable development of A. squamosa agriculture. This study provides the best strategy for scientific cultivation of A. squamosa in low-heat river valley areas.

Author Contributions

Conceptualization, W.W. and X.L.; data curation, T.B.; formal analysis, T.B.; funding acquisition, W.W.; methodology, W.W.; writing—original draft preparation, T.B.; writing—review and editing, T.B.; supervision, W.W. and X.L. All authors have read and agreed to the published version of the manuscript.

Funding

Fund of Less Developed Regions of the National Natural Science Foundation of China: 52169008; Basic Science Research Fund: Response mechanism and regulation strategy of soil carbon and nitrogen in Annona squamosa litchi-soybean intercropping system with water saving, nitrogen reduction and straw returning: 202401AS07005.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. The location of the experimental site.
Figure 1. The location of the experimental site.
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Figure 2. Precipitation and average daily temperature during the whole growth stage of cherimoya in 2022 and 2023.
Figure 2. Precipitation and average daily temperature during the whole growth stage of cherimoya in 2022 and 2023.
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Figure 3. The layout of the plot and the drip tape for Annona squamosa.
Figure 3. The layout of the plot and the drip tape for Annona squamosa.
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Figure 4. The spatio-temporal difference of soil moisture (%): (A) flower bud differentiation; (B) flowering and fruiting; (C) fruit swelling; (D) fructescence. Note: Different letters represent significant differences (p < 0.05). * p < 0.05. ** p < 0.01. ns, not significant at p > 0.05.
Figure 4. The spatio-temporal difference of soil moisture (%): (A) flower bud differentiation; (B) flowering and fruiting; (C) fruit swelling; (D) fructescence. Note: Different letters represent significant differences (p < 0.05). * p < 0.05. ** p < 0.01. ns, not significant at p > 0.05.
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Figure 5. Dynamic change in daily soil temperatures at 5 and 25 cm depths among various treatments at the experimental site.
Figure 5. Dynamic change in daily soil temperatures at 5 and 25 cm depths among various treatments at the experimental site.
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Figure 6. Effects of different treatments on Annona squamosa yield, single-fruit weight. Indicating different lowercase letters indicates significant differences between treatments at the p < 0.05 level.
Figure 6. Effects of different treatments on Annona squamosa yield, single-fruit weight. Indicating different lowercase letters indicates significant differences between treatments at the p < 0.05 level.
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Figure 7. Correlation analysis between the yield and quality of senna lychee and soil water content, soil temperature and growth under different treatments. SWC, soil water content; ST, soil temperature; 1, soil at the stage of flower bud differentiation; 2, soil at the stage of blossoming and fruiting; 3, soil at the stage of fruit expansion; 4, soil at the stage of ripening; LAI, leaf area index; NSL, new slightly longer; NSD, newly stemmed stubby. For example, SWC1, soil water content at the stage of flower bud differentiation. * To characterize the significance of correlations, * represents p < 0.05, ** represents p < 0.01, *** represents p < 0.001, and no * indicates p > 0.05.
Figure 7. Correlation analysis between the yield and quality of senna lychee and soil water content, soil temperature and growth under different treatments. SWC, soil water content; ST, soil temperature; 1, soil at the stage of flower bud differentiation; 2, soil at the stage of blossoming and fruiting; 3, soil at the stage of fruit expansion; 4, soil at the stage of ripening; LAI, leaf area index; NSL, new slightly longer; NSD, newly stemmed stubby. For example, SWC1, soil water content at the stage of flower bud differentiation. * To characterize the significance of correlations, * represents p < 0.05, ** represents p < 0.01, *** represents p < 0.001, and no * indicates p > 0.05.
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Table 1. Orthogonal test scheme.
Table 1. Orthogonal test scheme.
TreatmentsFactorsTreatments
Irrigation Levels (W)
mm		Fertilizer Amount (F)
kg·hm−2		Cover Measures (A)
T1W1 (55%FC)F1 (1666)A1 (no cover)W1F1A1
T2W1 (55%FC)F2 (2083)A2 (fresh grass cover)W1F2A2
T3W1 (55%FC)F3 (2500)A3 (straw cover)W1F3A3
T4W2 (65%FC)F1 (1666)A2 (fresh grass cover)W2F1A2
T5W2 (65%FC)F2 (2083)A3 (straw cover)W2F2A3
T6W2 (65%FC)F3 (2500)A1 (no cover)W2F3A1
T7W3 (75%FC)F1 (1666)A3 (straw cover)W3F1A3
T8W3 (75%FC)F2 (2083)A1 (no cover)W3F2A1
T9W3 (75%FC)F3 (2500)A2 (fresh grass cover)W3F3A2
Table 2. Effects of different treatments on new shoot growth and LAI.
Table 2. Effects of different treatments on new shoot growth and LAI.
Treatments20222023
New Shoot LengthNew Shoot DiameterLAINew Shoot LengthNew Shoot DiameterLAI
T130.43 ± 3.35 cd1.15 ± 0.05 abc2.23 ± 0.36 a34.12 ± 1.56 de0.75 ± 0.05 d2.53 ± 0.05 d
T230.61 ± 3.55 cd1.30 ± 0.03 a2.24 ± 0.27 a35.36 ± 2.63 d0.83 ± 0.07 bc2.60 ± 0.05 c
T331.27 ± 2.82 bc1.34 ± 0.05 ab2.26 ± 0.23 ac35.78 ± 3.24 d0.87 ± 0.09 bc2.62 ± 0.05 c
T435.20 ± 3.28 ab1.39 ± 0.03 ab2.42 ± 0.09 a39.22 ± 2.04 b0.92 ± 0.09 b2.89 ± 0.09 a
T535.57 ± 2.71 ab1.28 ± 0.06 d2.40 ± 0.16 a46.36 ± 2.45 a0.98 ± 0.06 ab2.96 ± 0.03 a
T636.33 ± 3.51 a1.29 ± 0.08 ab2.37 ± 0.2 a38.65 ± 2.96 c0.94 ± 0.07 b2.78 ± 0.04 b
T735.07 ± 2.37 ab1.33 ± 0.07 ab2.34 ± 0.19 c40.23 ± 3.38 b0.97 ± 0.06 ab2.73 ± 0.03 b
T835.35 ± 2.46 ab1.27 ± 0.07 cd2.29 ± 0.19 ab39.42 ± 2.06 b0.95 ± 0.07 b2.71 ± 0.06 b
T936.25 ± 2.46 a1.26 ± 0.06 bcd2.27 ± 0.22 a45.21 ± 2.48 a1.02 ± 0.06 a2.93 ± 0.06 a
W*ns******
F*nsnsns*ns
Ansnsnsns**ns
Note: Different letters indicate significant differences at the level of p < 0.05. * p < 0.05.** p < 0.01. ns, not significant at p > 0.05.
Table 3. Effects of different treatments on the nutrient composition of Annona squamosa.
Table 3. Effects of different treatments on the nutrient composition of Annona squamosa.
Treatment20222023
Soluble Solids
(%)		Soluble Sugar
(mg·g−1)		Sugar–AcidVitamin C
(mg100mL−1)		Soluble Solids
(%)		Soluble Sugar
(mg·g−1)		Sugar–AcidVitamin C
(mg100mL−1)
T120.32 ± 0.05 g167.56 ± 1.03 e66.5 ± 0.05 g36.61 ± 0.02 d21.12 ± 0.06 fg170.74 ± 1.23 f67.36 ± 0.07 g35.82 ± 0.04 cd
T222.41 ± 0.05 f173.89 ± 2.04 c67.8 ± 0.04 f36.82 ± 0.06 c21.91 ± 0.07 f176.59 ± 1.14 de68.88 ± 0.06 f36.30 ± 0.06 c
T323.62 ± 0.06 e177.32 ± 1.24 bc69.87 ± 0.07 d37.24 ± 0.05 ab23.12 ± 0.07 d179.66 ± 1.09 d69.97 ± 0.08 f36.85 ± 0.05 bc
T426.58 ± 0.04 c182.32 ± 1.21 b71.06 ± 0.07 cd37.564 ± 0.05 ab25.46 ± 0.05 c187.65 ± 1.36 b72.36 ± 0.07 c37.65 ± 0.05 ab
T528.94 ± 0.05 a194.69 ± 1.33 a73.56 ± 0.55 a37.92 ± 0.05 a28.76 ± 0.04 a195.79 ± 1.44 a74.67 ± 1.55 a38.23 ± 0.05 a
T627.56 ± 0.04 b183.78 ± 1.25 b72.49 ± 0.08 b37.62 ± 0.04 a26.56 ± 0.04 b182.58 ± 1.52 c73.59 ± 0.08 b37.92 ± 0.04 a
T723.46 ± 0.03 e174.45 ± 1.56 c70.33 ± 0.12 d37.11 ± 0.02 bc22.96 ± 0.06 e176.45 ± 0.09 de71.34 ± 0.18 d37.24 ± 0.03 b
T825.58 ± 0.07 d178.69 ± 1.67 b69.96 ± 0.05 d37.32 ± 0.04 ab24.68 ± 0.07 c172.69 ± 0.08 e70.23 ± 0.08 e37.57 ± 0.04 ab
T922.94 ± 0.05 f169.69 ± 1.35 d68.77 ± 0.04 e36.95 ± 0.04 c21.57 ± 0.06 f170.69 ± 1.03 f71.11 ± 0.07 d36.75 ± 0.04 bc
W*nsns*****
Fnsnsnsns*nsnsns
Ansnsnsnsns**ns
Note: MI represents index of fruit ripeness; different letters indicate significant differences at the level of p < 0.05. * p < 0.05. ** p < 0.01. ns, not significant at p > 0.05.
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Wang, W.; Bai, T.; Liu, X. Effects of Water, Fertilizer and Heat Coupling on Soil Hydrothermal Conditions and Yield and Quality of Annona squamosa. Agronomy 2024, 14, 2189. https://doi.org/10.3390/agronomy14102189

AMA Style

Wang W, Bai T, Liu X. Effects of Water, Fertilizer and Heat Coupling on Soil Hydrothermal Conditions and Yield and Quality of Annona squamosa. Agronomy. 2024; 14(10):2189. https://doi.org/10.3390/agronomy14102189

Chicago/Turabian Style

Wang, Weihua, Ting Bai, and Xingwen Liu. 2024. "Effects of Water, Fertilizer and Heat Coupling on Soil Hydrothermal Conditions and Yield and Quality of Annona squamosa" Agronomy 14, no. 10: 2189. https://doi.org/10.3390/agronomy14102189

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