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Article

Potential of Modified Reduced Tillage with Cover/Green Manure Crop for Climate Change Mitigation in a Smallholder Rainfed Farming System

by
Nabeeha Javed
1,
Shahzada Sohail Ijaz
1,*,
Qaiser Hussain
1,
Muhammad Ansar
2,
Abdulwahed Fahad Alrefaei
3,
Bader O. Almutairi
3,
Wajid Zaman
4,* and
Munazza Yousra
5
1
Institute of Soil & Environmental Sciences, PMAS Arid Agricultural University, Rawalpindi 46000, Pakistan
2
Department of Agronomy, PMAS Arid Agricultural University, Rawalpindi 46000, Pakistan
3
Department of Zoology, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
4
Department of Life Sciences, Yeungnam University, Gyeongsan 38541, Republic of Korea
5
Land Resources Research Institute, NARC, Islamabad 45500, Pakistan
*
Authors to whom correspondence should be addressed.
Sustainability 2024, 16(11), 4781; https://doi.org/10.3390/su16114781
Submission received: 25 April 2024 / Revised: 31 May 2024 / Accepted: 3 June 2024 / Published: 4 June 2024
(This article belongs to the Topic Climate Change Impacts and Adaptation: Interdisciplinary Perspectives)
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Versions Notes

Abstract

:
Soil can function as a reservoir and a source of greenhouse gases (GHGs), contingent on its management. This study assesses the potential of a modified reduced tillage (MRT) approach involving the use of cover or green manure crops as a substitute for crop residues to mitigate GHG emissions from soil within smallholder rainfed farming systems. A two-year field experiment with different tillage techniques (moldboard plow, tine cultivator, and modified reduced tillage) and crop rotations (summer fallow–wheat and cover/green manure–wheat) was conducted at Rawalpindi, Pakistan. The results showed that MRT reduced carbon dioxide (CO2) and nitrous oxide (N2O) emissions by 8% and 15.3%, respectively, from soil while maintaining consistently higher soil moisture than conventional tillage techniques. The modified reduced tillage reduced the global warming potential (GWP) and greenhouse gas intensity (GHGI) by 15.8% and 20.7%, respectively. The net ecosystem exchange (NEE) was unaffected by the tillage systems. Therefore, adopting the MRT technique and incorporating green manure is a viable strategy for curtailing GHG emissions from soil, particularly in the context of smallholder rainfed farming systems. Extended, multi-year studies under various climate scenarios and agronomic practices are needed to understand the long-term impacts of MRT and crop rotations on GHG emissions.

1. Introduction

Greenhouse gases, including carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4), are being released into the atmosphere at an accelerated rate [1], resulting in various adverse effects, such as global warming [2]. Agriculture is accountable for approximately 12% of human-caused greenhouse gas emissions [3]. The primary contributors to agriculture are arable soils (5.27%) and animal intestinal fermentation (3.21%) [4,5]. Consequently, there has been a growing emphasis on the potential of soil to function as a sink and source of atmospheric gases, contingent on its management [6]. Soil respiration significantly impacts the global carbon cycle by releasing CO2 from the carbon pool of soil into the atmosphere [7]. Soil organic carbon (SOC) plays a critical role in the global carbon cycle, serving as the most substantial terrestrial carbon reservoir following fossil fuel deposits [8]. This means it contains substantial carbon that is vital for maintaining the atmospheric carbon balance [9]. Even slight changes in SOC resulting from shifts in agricultural practices can influence the global carbon balance because it is a substantial reservoir of soil organic carbon in terrestrial ecosystems [8]. Increasing soil organic matter (SOM) and soil carbon stocks are crucial for climate change mitigation and adaptation, owing to their profound effects on carbon sequestration, greenhouse gas emissions reduction, soil health, and ecosystem resilience [9]. Furthermore, nitrification and denitrification processes within the soil contribute to N2O production, a significant greenhouse gas [10]. The application of nitrogenous fertilizers to enhance crop productivity amplifies N2O emissions [11]. Agricultural soils generally range from minor CH4 emitters to small CH4 sinks in the atmosphere [12]. The interplay between the soil carbon changes and N2O emissions predominantly governs the global warming potential (GWP) [13], which provides an overall assessment of greenhouse gas sources and sinks within a crop production system. Conventional cropping patterns often result in a net release of CO2 and N2O, diminishing the atmospheric CH4 sink [14].
Conservation tillage is being increasingly adopted worldwide, presenting a practical approach for soil conservation, enhanced crop productivity, and reduced input expenses [15,16,17]. In addition, conservation tillage is recommended as a strategy to mitigate the GWP caused by N2O and CH4 emissions during crop cultivation because of its capacity for soil carbon storage [18]. Conservation tillage has positive effects on the soil properties, including improved soil organic carbon, increased moisture retention, reduced soil bulk density, satisfactory crop yields, and economic returns [19].
The Pothwar Plateau in Pakistan is a semi-arid region characterized by its hilly terrain, limited water resources, and highly variable rainfall patterns [20]. These conditions make sustainable agricultural practices essential for enhancing productivity and preserving soil health [21]. Among the various soil management strategies, biofilm mulching has become a promising technique [22]. Biofilm mulch conserves soil moisture by reducing evaporation, moderating soil temperature, suppressing weed growth, and improving soil structure [23]. Biofilm mulching does not mitigate GHG emissions directly, but can complement other sustainable approaches by maintaining favorable microclimate conditions that reduce the need for frequent tillage [24]. The cost and availability of biofilm materials and varying degradation rates can limit their widespread use and require careful disposal to avoid soil contamination [25,26,27]. The Pothwar Plateau covers an area of approximately 1.8 million hectares, and approximately 80% of farmers in the region adopt the practice of summer fallowing that involves intensive plowing with a moldboard plow and tine cultivator [28]. Previous research in the region has confirmed the benefits of reduced tillage, specifically chisel plowing with crop residue retention, which enhances moisture conservation, soil carbon sequestration, aggregate formation, and wheat yield compared to conventional tillage methods [28,29]. No-till and minimum tillage have limitations because of reduced rainwater infiltration and lower crop yields [30]. Consequently, local farmers are more likely to adopt reduced tillage. The primary challenge in promoting reduced tillage is the availability of crop residue, which farmers often use as feed for their livestock. Incorporating cover/green manure crops during the summer fallow period offers an alternative to crop residue, providing soil cover during the heavy monsoon rains to conserve moisture, prevent soil erosion, suppress weeds, and enhance soil organic matter. Despite these insights, the comprehensive impacts of reduced tillage on GHG emissions, GWP, and GHGI in smallholder rainfed farming systems are unclear. This study hypothesizes that implementing a modified reduced tillage system and a cover/green manure crop can mitigate GHG emissions. Consequently, this research was conducted in Pakistan’s Pothwar plateau with the following objectives: (1) quantify GHG emissions, (2) assess the global warming potential, and (3) evaluate the greenhouse gas intensity associated with modified, reduced tillage practices compared to conventional tillage methods.

2. Materials and Methods

2.1. Site, Treatments, and Experimental Design

A two-year field study was conducted at the Research Farm of Pir Mehr Ali Shah, Arid Agriculture University in Rawalpindi, Pakistan (32°10′ N, 73°55′ E), from 2018–2020. The research site is located within the Pothwar plateau in northern Punjab province, which has a subtropical dryland climate. Annual rainfall ranges from 400 mm in southern areas to 1137 mm in northern areas, with approximately 65% occurring during the July–August monsoon months. During this period, local farmers practice summer fallowing and intensive plowing with a moldboard plow and a frequent tine cultivator to conserve moisture and manage weeds before wheat planting in November. The study was conducted in an existing long-term experiment initiated in 2011 comparing conservation tillage systems to conventional tillage. The experimental site has sandy clay loam soils classified as Udic Haplustalfs. The soil has 51% sand, 27% silt, and 21% clay, with intermediate drainage. It has an alkaline pH of 7.87 and no salinity issues (electrical conductivity: 0.57 dS/m). The nitrate and available phosphorus levels are deficient at 4.3 mg/kg and 3.8 mg/kg, respectively. Organic matter content is relatively low at 5.04 g/kg compared to the critical limit, while extractable potassium is adequate at 138 mg/kg [30].
This study used a split-plot randomized complete block design with three replications. The primary plots accommodate the tillage systems, while the sub-plots pertain to crop rotations: (a) fallow–wheat (F–W), and (b) cover/green manure crop-wheat (GM–W). The main plots measured 13 m × 10 m, and the sub-plots measured 4 m × 10 m. The tillage treatments were started in July in each main plot. Subsequently, each main plot was subdivided into two subplots. The first subplot (fallow–wheat rotation) remained uncultivated from July to October, with weed control achieved through repeated tine cultivator tillage. The second subplot (green manure–wheat) involved sowing sesbania at a seed rate of 40 kg /ha in July, followed by green manuring at flower initiation towards the end of September. Wheat was sown at a seed rate of 100 kg/ha across all main and subplots on November 15, with the application of urea 100 kg/ha and diammonium phosphate 50 kg/ha fertilizer.

2.2. GHG Measurements and Calculations

A collar equipped with a groove was positioned randomly in the field, and a chamber rim was inserted into this groove to quantify gas evolution. The rate of soil CO2 was assessed using the CO2 Analyzer (Lutron GC-2028, Lutron, Coopersburg, PA, USA). Gas samples were collected weekly during the initial month of primary tillage, bi-weekly during the subsequent month, and monthly throughout the year. This sampling regimen was consistent across both experimental years (2018 to 2020). From July 2019 to July 2020, the CH4 and N2O fluxes were monitored using a static chamber technique. Although the static chamber technique is widely accepted for its simplicity and cost-effectiveness, it has inherent limitations in capturing the spatial and temporal variability of greenhouse gas emissions. Several strategies were used to mitigate these limitations. Repeated measurements were taken throughout different seasons to capture the temporal variability. The spatial variability was addressed by taking replicated measurements within each treatment plot. Standardized protocols were used for chamber placement, sampling time, and gas analysis to ensure the consistency and reliability of the data. The chamber, constructed from PVC and measuring 0.342 m, was placed randomly in the field to capture the gas emissions. Portable infrared methane gas detectors ((ATO-GAS-CH4) and (ATO-GAS-N2O), Australian Taxation Office, Canberra, Australia) were used to detect the gases within the chamber. The soil water content at a depth of 0–15 cm was assessed using time domain reflectometry (TDR, Mogadore, OH, USA), and the temperature was measured with the help of a soil thermometer to a 5 cm depth [31]. The environmental data were synchronized with GHG flux measurements by aligning the timestamps of the recorded data. The GHG flux data were logged concurrently with the environmental measurements to ensure temporal alignment.

2.3. GHG Data Analysis

The rate of GHG emissions from the soil surface was calculated by measuring the change in gas concentration over 15 min using four samples. The average flux and standard deviation were then calculated from three plots. The formula used to calculate the gas emission rate was the following:
f = Δ C / Δ t · V / A · m / V m
where ΔC/Δt, A, V, m, and Vm are the changes in gas concentration during chamber closure time, area of soil covered by the chamber, chamber volume, molecular weight of the gas, and gas molar volume, respectively. The results were then extrapolated to one hour and one square meter [32]. The gas emissions for each type of gas were converted to kg CO2-C per hectare per hour using the methodology reported elsewhere [33]. Negative fluxes indicate that the soil is absorbing gas, while positive fluxes indicate net emissions from the soil.
The net global warming potential (NGWP) equation given by [34] was used, in which the IPCC factors (34 and 298) for the conversion of CH4 and N2O to CO2 equivalent were used [35]. The GHGI was determined by dividing the NGWP by the grain yield of the wheat [presented elsewhere].
N G W P = 34 × C H 4   ( k g   h a − 1 ) + 298 × N 2 O   ( k g   h a − 1 ) + C O 2   ( k g   h a − 1 )
G H G I = N G W P / y i e l d ( k g   C O 2 − e q   k g − 1   g r a i n   y i e l d )
The net ecosystem exchange (NEE) of CO2 was calculated using the equation reported elsewhere [36], where NEE is the difference between total seasonal soil respiration (Rh) and net primary productivity (NPP):
N E E = R h – N P P
The NPP was calculated using the equation reported in a previous study [37], where NPP = 0.446 × Wmax × −0.00067. Here, Wmax stands for the maximum biomass.
Throughout the two-year study, weather data were collected continuously using an automatic weather station, which included information on rainfall and maximum and minimum daily temperatures. The annual precipitation during this period was 629.59 mm and 1014.26 mm in the first and second experimental years, respectively. In particular, the highest precipitation was recorded in June, with 137.51 mm and 178 mm in the first and second years, respectively. On the other hand, the lowest precipitation levels occurred in November of the first year (0.6 mm) and December of the second year (16 mm) (Figure 1).

2.4. Statistical Analysis

The collected data for various characteristics were analyzed using Analysis of Variance (ANOVA) within a split-plot design framework. The mean comparisons were conducted at the 5% significance level using a least significant difference (LSD) test. All statistical analyses were conducted using the software package Statistix 8.1 [38].

3. Results

3.1. Soil Moisture Content and Temperature

The MRT system consistently maintained a higher soil moisture content most of the year than the MB and TC systems, regardless of crop rotations (Figure 2). The mean soil moisture followed the MRT > MB > TC pattern across the growing seasons in both years. A comparison of the tillage and rotation combinations showed that the volumetric water content of the MB (F–W) combination exhibited a higher initial level in July, which gradually diminished over time. In November (at the time of wheat sowing), the MRT (GM–W) combination displayed elevated moisture levels in both years.
The soil moisture levels varied with weather conditions, peaking in August and declining by May. In the first year, the moisture content ranged from 21.58% in August to 9.8% in May. In the second year, it ranged from 21% in August to 9.68% in May. Tillage systems and green manuring had minimal impact on the average 24 month soil temperature across the experimental years. On the other hand, minor temperature fluctuations were observed during the fallow period without green manuring, with MB consistently having the highest temperatures and MRT and TC showing lower temperatures. The peak temperatures occurred from June to August.

3.2. CO2 Flux

The tillage systems significantly affected CO2 emissions, with MRT showing significantly lower emissions than the MB system. In both years, a combination of MRT with green manuring resulted in the lowest average emissions (187.65 mg/m2/h and 181.53 mg/m2/h in the first and second years, respectively), while MB plowing with F-W rotation recorded the highest (215.7 mg/m2/h and 209.24 mg/m2/h in the first and second years, respectively). Regardless of the tillage method and experimental year, GM–W rotation consistently had lower CO2 emissions than F–W rotation. An analysis of the sampling intervals showed that the peak CO2 emissions occurred immediately after primary tillage in July, averaging 279 mg/m2/h and 275 mg/m2/h in the first and second years, respectively. Two weeks post-tillage, the emissions subsided to an average of 188 mg/m2/h and 189 mg/m2/h in the first and second years, respectively. Subsequently, the emissions gradually rose, peaking in August before declining to their lowest levels in January, averaging 154 mg/m2/h and 152 mg/m2/h in the first and second years, respectively. Soil respiration fluxes followed a consistent pattern, peaking during the warm months and declining during the colder periods, often correlating with the changes in soil temperature (Figure 3).
The results indicated significant differences in cumulative CO2 emission among the tillage treatments and crop rotations (Figure 4). During both years, the cumulative CO2 was highest for the MB tillage and lowest for the MRT tillage, whereas the CO2 content of TC remained in between these two tillage systems. Among the crop rotations, the differences among GM–W and F–W were non-significant for all tillage treatments in the first year. On the other hand, when comparing the crop rotation effect in the second year, MRT and TC emitted significantly lower CO2 than the MB tillage.

3.3. N2O Fluxes

Throughout the sampling intervals, MRT with green manuring had the lowest average soil N2O emissions (0.20 mg/m2/h), while MB with the F–W rotation had the highest (0.24 mg/m2/h). The GM–W rotation generally had lower emissions than F–W, even though the emissions increased after green manure incorporation. The peak emissions occurred in July (0.30 mg/m2/h), with the lowest observed in February (0.16 mg/m2/h). Similar to CO2 emissions, the N2O fluxes were highest during the warm months and lowest during the cold periods, tracking soil temperature fluctuations. An examination of the cumulative N2O emissions revealed distinct effects of the tillage treatments and crop rotations. The cumulative N2O emissions were significantly lower under the MRT system than the MB and TC systems. Among the crop rotations, the cumulative N2O emissions were significantly lower under GM–W rotation than F–W rotation (Figure 5, Figure 6 and Figure 7).

3.4. Net Ecosystem Exchange (NEE), Global Warming Potential (GWP), and Greenhouse Gas Intensity (GHGI)

In the summer of the first year, the NEE for CO2 showed the highest value in MB, followed by TC, and the lowest in MRT. Higher NEE values were observed for the F–W crop rotations than GM–W. This pattern persisted in the second-year summer data. A comparison of the results for winter revealed a significant overall decrease in NEE for both years. The highest NEE was recorded in the MB (F–W) combination plots at 3.35 t C ha−1. The lowest was observed with the MRT (GM–W) combination plots at 2.55 t C ha−1 (Table 1).
The MB tillage system yielded the highest GWP, followed closely by TC, and the least under MRT in 2019–2020, because GWP is primarily influenced by N2O emissions because of its higher warming potential in both crop rotations (Table 2). Compared to the MB plots, both TC and MRT treatments resulted in a 6.57% and 14.11% reduction in GHGI, respectively, under the fallow–wheat crop rotation and by 11.58% and 20.7% under the green manure–wheat rotation (Table 2).

4. Discussion

4.1. Soil Moisture and Soil Temperature Affected by Different Tillage Practices and Crop Rotations

Minimizing tillage practices positively impacted soil properties, while excessive tillage practices negatively affected properties, such as the soil water content. A comparison among tillage systems showed that MRT resulted in a higher soil moisture content. This aligns with previous findings [39], in that chisel plow cultivation preserved the maximum moisture. Deep tillage practices, particularly with a chisel plow and disk, were reported to enhance soil water content, with shallow tillage having a less pronounced effect [40]. Green manure crops in the GM–W rotation absorbed moisture during their growth period, leading to less moisture conservation during summer than in the F–W rotation. On the other hand, after incorporating the green manure crop, particularly under MRT tillage, GM–W rotation consistently exhibited the highest moisture levels. This is crucial during wheat sowing in rainfed farming systems, where the combination of MRT tillage and GM–W rotation yielded the highest moisture content. Sesbania green manure incorporation adds organic matter to the soil, enhancing soil structure and water retention, as noted by [41].
These results revealed higher temperatures under moldboard plowing and chisel plowing for fallow–wheat rotation. This temperature increase was attributed to soil disturbance and closely linked to changes in the soil heat flux. Soil heat flux depends on the changes in soil heat capacity and thermal conductivity resulting from tillage practices, which impact soil structure, bulk density, and water content [42]. This finding relates to the impact of both MB and TC because they contribute to increased soil evaporation by inverting the soil during tillage, leading to higher soil temperatures [43]. The presence of a cover/green manure crop served as a surface cover with reduced heat conductivity and increased heat reflection compared to bare MB and TC because they contribute to increased soil evaporation by inverting the soil during tillage, leading to higher soil temperatures [43].

4.2. Effect of Tillage Practices and Crop Rotations on CO2 Emission

These results suggest that MRT yields lower CO2 emissions than MB. This reduction can be attributed to less soil disturbance in MRT, which reduces the exposure of soil organic matter to microbial decomposition [44]. The GM–W rotation consistently resulted in lower CO2 emissions than the F–W rotation, regardless of the tillage system or experimental year. This pattern was especially evident during the summer season. Integrating cover or green manure crops likely enhanced soil organic matter and microbial biomass, promoting carbon sequestration and reducing emissions [45]. CO2 emissions were highest immediately after primary tillage in July. This initial peak was attributed to the disruption of the soil structure and increased microbial activity that accelerates organic matter decomposition [46]. The emissions declined two weeks post-tillage, but peaked again in August before gradually decreasing to their lowest levels in January. The seasonal variation highlights the influence of temperature and microbial activity on CO2 emissions [47]. The findings are specific to the dryland conditions of the Pothwar plateau. The soil type, texture, and climatic conditions significantly influence CO2 emissions and may vary in other regions [48]. Although the two-year study provided valuable initial insights, longer-term experiments will be needed to assess the sustainability and cumulative impacts of MRT and crop rotations on CO2 emissions and soil health [49]. The peaks in CO2 emissions immediately after tillage suggest that the timing of the measurements critically affects the results. More frequent sampling could provide a detailed understanding of emission dynamics over time [50]. Furthermore, the variations in soil moisture, temperature, and organic matter content across different treatments may influence the microbial activity and CO2 emissions, necessitating controlled experimental conditions [51].

4.3. Impact of Tillage Practices and Crop Rotations on N2O Emissions

The N2O fluxes increased after plowing in the MB and TC systems and increased slightly after chiseling in the MRT system. Conventional tillage practices led to reduced bulk densities and smaller volumetric soil water content, improving the soil aeration and enabling N2O to escape before denitrification to N2 [52]. In contrast, the MRT and TC systems maintained a better soil structure and higher soil moisture content, which can suppress N2O emissions by promoting denitrification to N2, reducing the overall emissions [44,48]. Various factors, including water-filled pore space, mineral nitrogen concentration, air-filled porosity, soil moisture content, and soil structure density, contribute to increased N2O emissions following modified reduced tillage [53,54]. For example, a high soil moisture content can produce anaerobic conditions that favor denitrification. In contrast, well-aerated soils promote nitrification. Both can lead to increased N2O emissions depending on the specific soil and environmental conditions [55]. Significant N2O emissions were observed during the initial weeks of the fallow season, consistent with previous studies, suggesting that a lack of crop cover and increased soil aeration promote microbial processes that release N2O [56]. Overall, tillage systems did not significantly affect the total N2O emissions during the experimental period, but the MB treatment exhibited higher N2O fluxes during the fallow season than TC and MRT. Climate change impacts N2O emissions, with increased temperatures and precipitation contributing to elevated emissions. Sustainable tillage practices are crucial for mitigating greenhouse gas emissions, considering the interactions between climate and soil properties. The soil type and management strategies also influence N2O emissions, highlighting the importance of conservation practices in reducing emissions [57,58]. Additionally, organic matter contributions to nitrous oxide emissions following nitrate addition are not proportional to substrate-induced soil carbon priming, indicating that the relationship between soil management practices and N2O emissions can be complex, and are influenced by factors such as the type and quantity of organic matter present [59].

4.4. Net Ecosystem Exchange (NEE), Global Warming Potential (GWP), and Greenhouse Gas Intensity (GHGI) Influenced by Tillage Practices and Cropping Sequence

The net ecosystem exchange (NEE) of CO2 represents the balance between carbon (C) outputs from soil heterotrophic respiration (organic matter decomposition) and C inputs from autotrophic C assimilation (plant photosynthesis). The MRT system led to lower NEE, likely due to the treatment effects on the soil temperature, a strong driver of NEE CO2 [60]. The effect of temperature on soil, root, and leaf respiration contributed to this outcome. Both tillage practice and crop incorporation influence the soil temperature by altering the soil organic matter content, surface insulation, and radiation [61,62,63]. In green manure crop rotation, crop residues incorporated into the soil reduce heat input, resulting in lower NEE CO2 fluxes. On the other hand, plant residue incorporation removes this barrier between the soil and the atmosphere, allowing for heat exchange. The NEE CO2 was higher during the warm periods and varied with the crop growth stages, indicating the influence of seasonal temperature variations [64,65]. The net GWP was influenced significantly by N2O emissions and SOC sequestration [66]. Addressing this will require effective agricultural management approaches that maximize soil carbon storage and reduce N2O emissions in rainfed agriculture. This is crucial for mitigating greenhouse gas emissions and promoting sustainable productivity. The GHGI index is a useful tool for comparing the environmental and economic benefits of different agricultural management strategies, considering their impact on GHG emissions and crop yields [67]. The present study found that the variability in GHGI within modified reduced tillage treatments closely mirrored the variations in net GWP. While crop yield was pivotal in determining the GHGI, the N2O fluxes were the primary driver of GHGI variations, as reported elsewhere [65].
While the static chamber technique provided valuable data on GHG fluxes in this study, it is vital to consider the limitations of the method. The static chamber method can sometimes fail to capture the full extent of the spatial and temporal variability in greenhouse gas emissions. Variations in the soil type, moisture content, and temperature can lead to fluctuations in gas fluxes that static chambers might not fully capture.
These limitations were addressed by conducting repeated measurements across different intervals and following strict protocols for gas sampling and analysis. Nevertheless, these constraints should be considered when interpreting the results because they might have led to underestimations or overestimations of the actual gas fluxes.

5. Conclusions

This study’s findings suggest that transitioning from conventional tillage practices to modified reduced tillage, coupled with a cover/green manure crop, significantly reduce CO2 and N2O emissions, lowering the overall global warming potential and the greenhouse gas intensity. Peak emissions occurred in July, with the lowest levels occurring in February, indicating that fluxes were highest during warm months and lowest during cold periods, tracking soil temperature and moisture fluctuations. Conservation tillage approaches, such as MRT, are a promising avenue for climate-smart agriculture in smallholder rainfed areas of Pothwar and other similar regions. Future research will conduct extended, multi-year studies encompassing various climate scenarios and diverse agronomic practices that can provide a more comprehensive understanding of how modified reduced tillage affects greenhouse gas emissions over time.

Author Contributions

Conceptualization, Investigation, Validation, N.J., S.S.I., Q.H. and M.A.; Supervision, S.S.I.; Writing—original draft, N.J.; Methodology, Formal analysis, Data collection, N.J., S.S.I. and Q.H.; Writing—review and editing, N.J., S.S.I., Q.H., M.A., A.F.A., B.O.A., W.Z. and M.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This study received financial assistance from the Higher Education Commission of Pakistan under a project entitled “Inter-Comparison of CENTURY and DSSAT Model Simulations to Improve Soil Based Climate Change Resilience and Adaptability of Rainfed Crop Production Systems in Pakistan” (HEC Project No. 3179) and Researchers supporting project number (RSP2024R414), King Saud University, Riyadh, Saudi Arabia.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data will be given on request.

Acknowledgments

We extend our appreciation to the Researchers Supporting Project (no. RSP2024R414), King Saud University, Riyadh, Saudi Arabia.

Conflicts of Interest

The authors state that they have no known conflicting financial interests or personal connections that seem to have an impact on the work published in this article.

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Figure 1. Daily rainfall and average temperature during the experimental period 2018–2020.
Figure 1. Daily rainfall and average temperature during the experimental period 2018–2020.
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Figure 2. Soil moisture affected by the different tillage systems and crop rotations during 2018–2019 and 2019–2020. MB F–W (Moldboard with Fallow–Wheat); TC F–W (Tine cultivator with Fallow–Wheat); MRT F–W (Modified with Reduced tillage Fallow–Wheat); MB GM–W (Moldboard with Green manure–Wheat); TC GM–W (Tine cultivator with Green manure–Wheat); MRT GM–W (Modified Reduced tillage with Green manure–Wheat).
Figure 2. Soil moisture affected by the different tillage systems and crop rotations during 2018–2019 and 2019–2020. MB F–W (Moldboard with Fallow–Wheat); TC F–W (Tine cultivator with Fallow–Wheat); MRT F–W (Modified with Reduced tillage Fallow–Wheat); MB GM–W (Moldboard with Green manure–Wheat); TC GM–W (Tine cultivator with Green manure–Wheat); MRT GM–W (Modified Reduced tillage with Green manure–Wheat).
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Figure 3. Soil temperature affected by different tillage systems and crop rotations during 2018–2020. MB F–W (Moldboard with Fallow–Wheat); TC F–W (Tine cultivator with Fallow–Wheat); MRT F–W (Modified with Reduced tillage Fallow–Wheat); MB GM–W (Moldboard with Green manure–Wheat); TC GM–W (Tine cultivator with Green manure–Wheat); MRT GM–W (Modified Reduced tillage with Green manure–Wheat).
Figure 3. Soil temperature affected by different tillage systems and crop rotations during 2018–2020. MB F–W (Moldboard with Fallow–Wheat); TC F–W (Tine cultivator with Fallow–Wheat); MRT F–W (Modified with Reduced tillage Fallow–Wheat); MB GM–W (Moldboard with Green manure–Wheat); TC GM–W (Tine cultivator with Green manure–Wheat); MRT GM–W (Modified Reduced tillage with Green manure–Wheat).
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Figure 4. CO2 flux affected by different tillage systems and crop rotations during the experimental period 2018–2020. MB F–W (Moldboard with Fallow–Wheat); TC F–W (Tine cultivator with Fallow–Wheat); MRT F–W (Modified Reduced tillage with Fallow–Wheat); MB GM–W (Moldboard with Green manure–Wheat); TC GM–W (Tine cultivator with Green manure–Wheat); MRT GM–W (Modified Reduced tillage with Green manure–Wheat).
Figure 4. CO2 flux affected by different tillage systems and crop rotations during the experimental period 2018–2020. MB F–W (Moldboard with Fallow–Wheat); TC F–W (Tine cultivator with Fallow–Wheat); MRT F–W (Modified Reduced tillage with Fallow–Wheat); MB GM–W (Moldboard with Green manure–Wheat); TC GM–W (Tine cultivator with Green manure–Wheat); MRT GM–W (Modified Reduced tillage with Green manure–Wheat).
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Figure 5. Cumulative CO2 affected by different tillage systems and crop rotations during the experimental period 2018–2020. Treatments labeled with the same letter (e.g., “a”, “b”, “c”, etc.) within each crop are not significantly different from each other. Treatments labeled with different letters are significantly different from each other within each crop.
Figure 5. Cumulative CO2 affected by different tillage systems and crop rotations during the experimental period 2018–2020. Treatments labeled with the same letter (e.g., “a”, “b”, “c”, etc.) within each crop are not significantly different from each other. Treatments labeled with different letters are significantly different from each other within each crop.
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Figure 6. N2O flux affected by the different tillage systems and crop rotations during the experimental period 2019–2020. MB F–W (Moldboard with Fallow–Wheat); TC F–W (Tine cultivator with Fallow–Wheat); MRT FW (Modified Reduced tillage with Fallow–Wheat); MB GM–W (Moldboard with Green manure–Wheat); TC GM–W (Tine cultivator with Green manure–Wheat); MRT GM–W (Modified Reduced tillage with Green manure–Wheat).
Figure 6. N2O flux affected by the different tillage systems and crop rotations during the experimental period 2019–2020. MB F–W (Moldboard with Fallow–Wheat); TC F–W (Tine cultivator with Fallow–Wheat); MRT FW (Modified Reduced tillage with Fallow–Wheat); MB GM–W (Moldboard with Green manure–Wheat); TC GM–W (Tine cultivator with Green manure–Wheat); MRT GM–W (Modified Reduced tillage with Green manure–Wheat).
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Figure 7. Cumulative N2O affected by the different tillage systems and crop rotations during the experimental period 2019–2020. Letters denote homogeneous groups at α = 0.05 significance level, where treatments with the same letter are not significantly different from each other.
Figure 7. Cumulative N2O affected by the different tillage systems and crop rotations during the experimental period 2019–2020. Letters denote homogeneous groups at α = 0.05 significance level, where treatments with the same letter are not significantly different from each other.
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Table 1. Net ecosystem exchange (NEE) affected by different tillage and crop rotations during 2018–2020.
Table 1. Net ecosystem exchange (NEE) affected by different tillage and crop rotations during 2018–2020.
Tillage SystemsCrop RotationsSummer SeasonWinter SeasonAnnual
NEENEENEE
Mg ha−1
Year 2018–2019MBFW9.28 A3.35 A12.63 A
GW2.93 C2.08 A5.01 C
TCFW8.62 B1.91 A10.53 B
GW2.36 D2.95 A5.31 C
MRTFW8.54 B2.25 A10.79 B
GW1.93 D2.53 A4.46 C
Year 2019–2020MBFW8.44 A3.49 A11.93 A
GW2.14 B2.42 A4.56 B
TCFW7.90 A2.24 A10.24 A
GW1.58 B2.66 A4.24 B
MRTFW7.66 A2.65 A10.31 A
GW1.23 B4.00 A3.88 B
Different capital letters indicate statistically significant differences between means within each column at the 0.05 level. Means sharing the same letter are not significantly different from each other according to a post hoc test.
Table 2. Global warming potential (GWP) and greenhouse gas intensity (GHGI) affected by different tillage and crop rotations during 2018–2020.
Table 2. Global warming potential (GWP) and greenhouse gas intensity (GHGI) affected by different tillage and crop rotations during 2018–2020.
Tillage SystemsCrop RotationsGWP t C ha−1 year−1GHGI t C ha−1 year−1
Moldboard PloughFallow–Wheat93.90 A31.44 A
Green manure–Wheat89.94 AB28.95 BC
Tine CultivatorFallow–Wheat88.58 BC29.32 AB
Green manure–Wheat83.10 BCD25.14 CD
Modified Reduced TillageFallow–Wheat84.38 CD25.64 C
Green manure–Wheat77.65 D22.79 D
Different capital letters indicate statistically significant differences between means within each column at the 0.05 level. Means sharing the same letter are not significantly different from each other according to a post hoc test.
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Javed, N.; Ijaz, S.S.; Hussain, Q.; Ansar, M.; Alrefaei, A.F.; Almutairi, B.O.; Zaman, W.; Yousra, M. Potential of Modified Reduced Tillage with Cover/Green Manure Crop for Climate Change Mitigation in a Smallholder Rainfed Farming System. Sustainability 2024, 16, 4781. https://doi.org/10.3390/su16114781

AMA Style

Javed N, Ijaz SS, Hussain Q, Ansar M, Alrefaei AF, Almutairi BO, Zaman W, Yousra M. Potential of Modified Reduced Tillage with Cover/Green Manure Crop for Climate Change Mitigation in a Smallholder Rainfed Farming System. Sustainability. 2024; 16(11):4781. https://doi.org/10.3390/su16114781

Chicago/Turabian Style

Javed, Nabeeha, Shahzada Sohail Ijaz, Qaiser Hussain, Muhammad Ansar, Abdulwahed Fahad Alrefaei, Bader O. Almutairi, Wajid Zaman, and Munazza Yousra. 2024. "Potential of Modified Reduced Tillage with Cover/Green Manure Crop for Climate Change Mitigation in a Smallholder Rainfed Farming System" Sustainability 16, no. 11: 4781. https://doi.org/10.3390/su16114781

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