*Article* **Productivity and Nutrient Balance of an Intensive Rice–Rice Cropping System Are Influenced by Different Nutrient Management in the Red and Lateritic Belt of West Bengal, India**

**Tanmoy Shankar 1, Ganesh Chandra Malik 2, Mahua Banerjee 2, Sudarshan Dutta 3, Sagar Maitra 1, Subhashisa Praharaj 1, Masina Sairam 1, Duvvada Sarath Kumar 1, Eldessoky S. Dessoky 4, Mohamed M. Hassan 4,\*, Ismail A. Ismail 4, Tarek Saif 5, Milan Skalicky 6, Marian Brestic 6,7 and Akbar Hossain 8,\***

	- <sup>7</sup> Department of Plant Physiology, Slovak University of Agriculture, Nitra, Tr. A. Hlinku 2, 949 01 Nitra, Slovakia
	- <sup>8</sup> Bangladesh Wheat and Maize Research Institute, Dinajpur 5200, Bangladesh
	- **\*** Correspondence: m.khyate@tu.edu.sa (M.M.H.); akbarhossainwrc@gmail.com (A.H.)

**Abstract:** Rice is the lifeline for more than half of the world population, and in India, in view of its huge demand in the country, farmers adopt a rice–rice cropping system where the irrigation facility is available. As rice is a nutrient-exhausting crop, sustainable productivity of rice–rice cropping system greatly depends on appropriate nutrient management in accordance with the inherent soil fertility. The application of an ample dose of fertilizer is the key factor for maintaining sustainable rice yields and nutrient balance of the soil. Considering the above facts, an experiment was conducted on nutrient management in a rice–rice cropping system at the university farm of Visva-Bharati, situated in a sub-tropical climate under the red and lateritic belt of the western part of West Bengal, India, during two consecutive years (2014–2016). The experiment was laid out in a Randomized Completely Block Design with 12 treatments and three replications, with different rates of N:P:K:Zn:S application in both of the growing seasons, namely, *kharif* and *Boro*. The recommended (ample) dose of nutrients was 80:40:40:25:20 and 120:60:60:25:20 kg ha−<sup>1</sup> of N:P2O5:K2O:Zn:S in the *Kharif* and *Boro* season, respectively. A high yielding variety, named MTU 7029, and a hybrid, Arize 6444 GOLD, were taken in the *Kharif* and *Boro* seasons, respectively. The results clearly indicated that the application of a recommended dose of nutrients showed its superiority over the control (no fertilizer application) in the expression of growth characters, yield attributes, yields, and nutrient uptake of *Kharif* as well as *Boro* rice. Out of the all treatments, the best result was found in the treatment where the ample dose of nutrients was applied, resulting in maximum grain yield in both the *Kharif* (5.6 t ha<sup>−</sup>1) and *Boro* (6.6 t ha<sup>−</sup>1) season. The corresponding yield attributes for the same treatment in the *Kharif* (panicles m<sup>−</sup>2: 247.9; grains panicle−1: 132.0; spikelets panicle−1: 149.6; test weight: 23.8 g; and panicle length: 30.6 cm) and *Boro* (panicles m<sup>−</sup>2: 281.6; grains panicle−1: 142.7; spikelets panicle−1: 157.2; test weight: 24.8 g; and panicle length: 32.8 cm) season explained the maximum yield in this treatment. Further, a reduction or omission of individual nutrients adversely impacted on the above traits and resulted in a negative balance of the respective nutrients. The study concluded that the application of a

**Citation:** Shankar, T.; Malik, G.C.; Banerjee, M.; Dutta, S.; Maitra, S.; Praharaj, S.; Sairam, M.; Kumar, D.S.; Dessoky, E.S.; Hassan, M.M.; et al. Productivity and Nutrient Balance of an Intensive Rice–Rice Cropping System Are Influenced by Different Nutrient Management in the Red and Lateritic Belt of West Bengal, India. *Plants* **2021**, *10*, 1622. https:// doi.org/10.3390/plants10081622

Academic Editors:

Przemysław Barłóg, Jim Moir, Lukas Hlisnikovsky and Xinhua He

Received: 1 June 2021 Accepted: 3 August 2021 Published: 6 August 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

recommended dose of nutrients was essential for proper nutrient balance and sustainable yields in the rice–rice cropping system.

**Keywords:** nutrient management; rice–rice cropping system; growth characters; yield attributes; productivity; nutrient uptake and balance

#### **1. Introduction**

Rice is one of the most important cereals consumed across the globe and grown in different environmental conditions. A rice–rice cropping system is usually practiced by farmers where sufficient irrigation is available or in favorable lowland rainfed areas [1,2]. Apart from irrigation availability, high consumer demand, a relatively stable market price, and assurance of a minimum support price by the government encourage the farmers to grow two rice crops continuously in consecutive seasons. Though the rice–rice system seems to be feasible from a farmer's perspective, cereal–cereal cropping systems are often considered unsustainable and are discouraged [3] in terms of nutrient balance in the soil as well as agricultural sustainability [4]. Rice, being a nutrient intensive crop, absorbs a high amount of nutrients. Thus, a rice–rice system is expected to be even more nutrient exhaustive. Unless proper nutrient management practices are followed, soils may develop severe nutrient deficiency over a period of time, negatively affecting agricultural sustainability [5]. Rice–rice cropping systems are most prevalent across a major portion of India as well as South Asia, especially among small and marginal farmers.

Nitrogen (N), phosphorus (P), and potassium (K) are considered as primary nutrients and are very important for the growth and development of rice [6]. Nitrogen is responsible for vegetative growth, improving the leaf area index, chlorophyll synthesis, and so on [7]; thus, increasing photosynthesis and assimilate production in plants. N is deficient in most of the rice-growing areas, which requires a proper focus on nitrogen nutrition [8]. Phosphorus is known for its role in root growth, root development, and reproduction [9]. P is also known to improve tillering and promotes early flowering. Potassium, though not a constituent of organic structures of plants, is very important for plant strength, resistance to biotic and abiotic stresses, and stomatal activity [10]. In addition to primary nutrients, sulphur (S), a secondary plant nutrient, also plays a vital role in plant growth and development as S performs its distinctive role in protein and chlorophyll synthesis [11]. In addition to macronutrients, rice crop also requires micronutrients for completing its life cycle and proper nutrition. Among the different micronutrients, deficiency in zinc (Zn) is commonly observed in rice-growing areas [12], where close to 50% of soils in rice-growing tracts are deficient in Zn [13]. Zinc takes part in the carbohydrate transformation and it is an essential constituent of enzymes such as carbonic anhydrase, superoxide dismutase, and alcohol dehydrogenase [14]. Zinc is also involved in the auxin biosynthesis process. Soil submergence, which is commonly practiced in rice cultivation, results in a deficiency of Zn. Unlike macronutrients, the availability of Zn is higher at a low pH. Alkaline or calcareous soils may result in Zn deficiency [15].

A rice–rice cropping system, when practiced, removes nutrients from the same soil depth continuously. If the crops cultivated in a cropping system have a similar nutrient demand and the removal pattern of nutrients from the soil is also the same, then, unless proper care is taken to replenish the nutrient taken up by the crop, a single or multiple nutrient deficiencies may develop over a period of time [16]. Understanding the role of different nutrients in the growth and yield of rice is essential to provide essential nutrients in the required quantity to obtain higher productivity. However, higher productivity should also be sustainable to achieve long-term food security goals.

Imbalanced nutrient application is one of the most important reasons for multinutrient deficiency [17]. As the application of nitrogen increases plant dry matter production, a high amount of nitrogen is also expected to increase the uptake of other nutrients. Unless a sufficient amount of other nutrients is applied under such conditions, the crop will continuously drain the native soil nutrients. This, when practiced continuously over years, causes a deficiency in nutrients. Application of nutrients in adequate amounts and suitable proportion is the key to crop nutrition. As the application of all the essential nutrients is practically impossible, those nutrients whose deficiency is prevalent or the nutrients which are yield limiting should be given priority in the nutrient management plan. In addition to those nutrients, nutrients that are expected to be deficient due to huge removal by crops over years in a particular cropping system must be replenished regularly to avoid the development of new nutrient deficiencies. For understanding these phenomena, knowledge regarding the role of important nutrients such as N, P, K, S and Zn in crop growth and yield should be considered. The nutrient balance in the cropping system also should be studied to understand the nutrient removal pattern of the crops under different nutrient combinations.

The soil and agro-climatic conditions of the red and lateritic belt are unique, and the rice-based cropping system is predominant in the region. The improvement of irrigation facilities and adaptation of HYVs and hybrids attracted farmers to adopt a rice–rice cropping system. As this cropping system is nutrient exhaustive, the development of multi-nutrient deficiency has been observed in recent times [18], drawing the attention of researchers. Similar observations on fertility degradation due to the rice-based cropping system were also noted in Southeast Asia [19]. Under these circumstances, there is an urgent need for balanced nutrient management in intensive cropping systems as a cost-effective and environmentally friendly approach to achieve agricultural sustainability in the region. Taking into consideration the above facts, an experiment was performed to evaluate the impact of different nutrients (inclusive of omission of specific nutrients) management on the growth and productivity of rice in a rice–rice cropping system. The uptake and nutrient balance are also studied to understand the necessity of nutrient supplementation to avoid long-term nutrient deficiencies in a rice–rice cropping system.

#### **2. Materials and Methods**

#### *2.1. Experimental Site*

The site of the field trial was the university farm of Visva Bharati (20◦39 N latitude and 87◦42 E longitude, with an altitude of 58.9 m above M.S.L.), situated in a sub-tropical climate under the red and lateritic belt of the western part of West Bengal, India [20]. The soils of the field trial were sandy loam soil belonging to the typical Ultisols. The characteristics and initial fertility of the experimental soil are described in Table 1.

**Table 1.** Characteristics and initial fertility of the experimental soil and methodologies followed for determination of soil quality.


The location falls in the region of the southwest monsoon, and monsoon rains generally start from the end of June and continue up to mid-October, with an average annual rain of 1377 mm. Out of the total annual rain, monsoon rain constitutes about 80–90%. The meteorological information, such as the maximum and minimum temperature (◦C), rainfall (mm), and relative humidity (%) during the period of experimentation (July 2014–June 2016), were received from the meteorological observatory of the Institute of Agriculture, Sriniketan, and is presented in Figure 1.

**Figure 1.** Meteorological data during the crop season (July 2014 to June 2016).

#### *2.2. Experimental Design and Treatments*

The experiment on nutrient management in the rice–rice cropping system was carried out for two years (four cropping seasons): 2014–2015 and 2015–2016. The experiment was laid out in a Randomized Complete Block Design (RCBD) with twelve treatments (net plot area of 5 m × 4 m each) and we repeated all treatments three times. The treatments were in the *Kharif* season: T1: N80P40K40Zn25S20; T2: N40P40K40Zn25S20; T3: N0P40K40Zn25S20; T4: N80P20K40Zn25S20; T5: N80P0K40Zn25S20; T6: N80P40K20Zn25S20; T7: N80P40K0Zn25S20; T8: N80P40K40Zn12.5S20; T9: N80P40K40Zn0S20; T10: N80P40K40Zn25S10; T11: N80P40K40Zn25S0; and T12: control, (without any fertilizer); whereas in the *Boro* season: T1: N120P60K60Zn25S20; T2: N60K60Zn25S20; T3: N0K60Zn25S20; T4: N120P30K60Zn25S20; T5: N120P0K60Zn25S20; T6: N120P60K30Zn25S20; T7: N120P60K0Zn25S20; T8: N120P60K60Zn12.5S20; T9: N120P60K60Zn0S20; T10: N120P60K60Zn25S10; T11: N120P60K60Zn25S0; and T12: control (without any fertilizer). The recommended (ample) dose of nutrients was 80:40:40:25:20 and 120:60:60:25:20 kg ha−<sup>1</sup> of N:P2O5:K2O:Zn:S in the *Kharif* and *Boro* season rice, respectively, and the treatment T1 received an ample dose of nutrients in both the seasons. In the case of T2, P, K, S, and Zn were applied in an ample dose, and 50% of the N was applied. In T3, N, K, S, and Zn were applied with an ample dose, 0% of N applied, and the same manner was applied for the remaining treatments up to T11, but in T12, no fertilizer was applied and considered as the control. The total amount of P, K, Zn, and S were applied as basal, while nitrogen was applied in three splits. The HYV and hybrid of rice were taken in the *Kharif* and *Boro* season with the same duration (Table 2).


**Table 2.** Variety/hybrid chosen, date of transplanting, and duration of rice (2014–2016).

#### *2.3. Cultural Practices*

The standard procedure of rice cultivation in the locality was adopted for both seasons. The treated seeds (with Carbendazim at the rate of 2 g kg−<sup>1</sup> of seed) were sown in the nursery during both seasons and the seeds were covered lightly with soil. For the main field preparation, the soil was first tilled thoroughly cross wise with a tractor-drawn harrow at an optimum moisture condition. Then tillage was done with a mouldboard plough (25 cm deep) to obtain a good tilth and it was followed by planking. The clods and stubbles of previous crops were removed from the land. The field was flooded with water and the puddling was done under saturated moisture conditions prior to three days of transplanting. After proper levelling, the field was laid out by making net plots (5 m × 4 m each), plot bunds, and channels for irrigation and drainage. After completion of the layout, nutrients were applied as per the treatments. The sources of nitrogen, phosphate, potash, sulphur, and zinc were urea, diammonium phosphate (DAP), muriate of potash (MOP), Bentonite-S (90% of S), and Zn-Ethylenediamine tetraacetic acid (EDTA), respectively. Among the different fertilizers, nitrogen was applied in splits. Half of the nitrogen and a full quantity of the other nutrients were applied as the basal treatment; however, the rest of the N was top-dressed in two equal splits during the maximum tillering and panicle initiation stages for *Kharif* as well as for *Boro* rice.

The 21-day old seedlings were transplanted in the main field at a spacing of 20 cm × 15 cm. In each hill, three seedlings were transplanted. The weeds were removed by hand weeding at early tillering (20 days after transplanting (DAT) and late tillering (40 DAT)). After transplanting, the field was kept saturated with moisture for three weeks to facilitate tillering and followed by a water stagnation of 5 ± 2 cm was maintained up to physiological maturity. Before topdressing of N, standing water was removed from the rice field and irrigated again on the next day and water stagnation was maintained. Ten days prior to harvest, stagnant water was removed. In the *Kharif* season, four irrigations were applied, whereas the in *Boro* season, the crop required six irrigations. The crop faced a mild attack of yellow stem borer and recommended protocols of the university were adopted to manage the pest. However, crop damage due to pest attacks were negligible. The crop was harvested from each net plot manually when it reached 80% maturity. The harvested crop was threshed, winnowed, and the sun-dried weight was recorded at 12% moisture.

#### *2.4. Measurements and Analytical Procedures*

#### 2.4.1. Growth and Yield Attributes

The third rows from the border of each side of a plot were sampled to record biometric observations. Different growth characters, namely, plant height, dry matter accumulation, leaf area index (LAI), and number of tillers were recorded at different growth stages (20, 40, 60, 80, 100, and 120 days after transplanting, DAT) and the crop growth rate (CGR) was calculated for different periods of the rice–rice cropping system for two consecutive years. For measurement of dry matter accumulation, five randomly selected plants were taken as a destructive sample; the leaves were separated, drying the leaves and the remaining portion of the plant separately in an oven to obtain constant weight (for 48 h at 65 ◦C). The area of the green leaves taken from the destructive samples was recorded by leaf area meter (Model No: WDY- 500 A, Swastik Scientific Company, India). The ratio of the leaf area weight of these leaves was used to measure the LAI (Equation (1)) [28]. In the case of

yield attributes, ten plants from a plot were randomly marked and at crop maturity; these were harvested, dried, and data on the yield parameters were noted.

$$\text{Leaf area index} = \frac{\text{leaf area}}{\text{ground area}} \tag{1}$$

2.4.2. Collection and Analysis of Plant and Soil Samples

N, P, K, S, and Zn content in plant samples was determined by the standard procedures (Table 1). Plant samples required for the determination of P, K, S and Zn were taken treatment wise after noting down the yields data and dried at 65 ◦C, pulverized, and digested in di-acid (9:4 *v*/*v*) of nitric acid (HNO3)/perchloric acid (HClO4). The nutrient content in straw and grain of rice was measured and nutrient uptake was determined by multiplying the nutrient content with the corresponding straw and grain yield [21].

$$\text{Nutrients uptake} \left(\text{kg ha}^{-1}\right) = \frac{\% \text{ mutant content in grain or starw} \times \text{dry matter}}{100} \tag{2}$$

Initial soil sample (0–15 cm) was collected prior to cultivation of *Kharif* rice in June 2014 and it was considered for determination of soil characteristics and initial fertility. After each harvest again soil samples were collected treatment wise to obtain the post-harvest soil nutrient status and it was further considered as the initial soil fertility for the next crop. Likewise, the final soil samples were collected in May 2016 after the harvest of *boro* rice. Collected soil samples were air-dried and ground to pass through a 2-mm stainless steel sieve for determination of soil parameters by standard methods as mentioned in Table 1. The initial soil fertility has also been mentioned in Table 1, however, the nutrient balance has been calculated crop-wise as well as for the system.

#### 2.4.3. Nutrient Balance

The balance sheet of available nutrients was computed by using the following formulae given by Tandon [29] (Equation (3)). The determined nutrient balance may be positive or negative.

Nutrient balance kg ha−<sup>1</sup> = Available soil nutrient status − Initial soil status before each crop (3)

#### *2.5. Calculations and Statistical Analysis*

The experimental data were analysed statistically by using analysis of variance (ANOVA). The standard error of the mean (SEm±) and critical difference at 5% probability level of significance (CD, *p* ≤ 0.05) [30] were calculated. The software used in the statistical analysis and drawing figures (including regression curve) was Excel from Microsoft Office Home and Student version 2019-en-us, Microsoft Inc., Redmond, Washington (DC, USA).

#### **3. Results and Discussion**

#### *3.1. Growth Parameters*

Different growth characteristics were calculated for the different periods of the rice– rice cropping system for two consecutive years. The data on plant height (Table 3) revealed that application of an ample dose of nutrients in *Kharif* rice (i.e., T1: N80P40K40Zn25S20) triggered a significant increase in height of the rice plants over the control (i.e., T12: no fertilizer) at different days after transplanting (DAT) in both years. The treatment N80P40K40Zn25S20 (T1) produced the tallest rice plants in both years, while the shortest plant was observed in the control plots. However, the treatments T2, T4, T6, T8, and T10 were statistically on par with the enhancement of plant height in both years.


= coefficient of variation; \*\* and \* significant at *p* ≤ 0.01 and *p* ≤ 0.05, respectively; NS = not significant; different letters within the continuous columns indicate significant differences at the 1% level of probability.

In the case of *Boro* rice, the application of T1 also produced the longest plants at all growth stages amongst all other treatments during the two years of study (2014–2015 and 2015–2016). The observation clearly showed that the application of 100% recommended dose of N:P:K:Zn:S (also termed as ample dose) increased the plant height at the different growth stages of rice irrespective of seasons, probably because of the proper nutrition obtained by the said treatment. Similar findings were also noted by earlier researchers [31], who also revealed that the application of balanced nutrients in a crop improved the growth and development of plants.

Dry matter accumulation of the *Kharif* and *Boro* rice in both years (2014 and 2015) was influenced by different levels of nutrients and there was an enhancement in dry matter with the progression of crops towards maturity (Table 4). A strong interrelationship between dry matter accumulation and yield was observed (R2 being 0.83 and 0.89, respectively, for the *Kharif* and *Boro* seasons). The treatment T1 in both the *Kharif* and *Boro* seasons resulted in the production of the maximum dry matter at all growth stages. The treatment T1 in *Kharif* rice increased the dry matter production significantly in both seasons over T3, T5, T7, T9, T11, and the control, but the treatment T1 was statistically on par with T2, T4, T6, T8, and T10.

A similarity between the two years was noted in *Boro* rice where T1 expressed its significant superiority over the control (T12, no fertilizer) as observed in different growth stages and T3 was statistically on par with control at the harvesting stage during both years of study. The ample dose of nutrients (T1) produced significantly more dry matter than T3, T5, T7, T9, T11, and the control. Although, treatment T1 was statistically on par with the T2, T4, T6, and T10 treatments in both seasons. The maximum dry matter in the T1 treatment was due to the application of 100% of the recommended dose of N:P:K:Zn:S that facilitated access to the required nutrients involving in dry matter production; this assumption was also confirmed by earlier studies [32,33].

The data on *Kharif* and *Boro* rice for LAI was measured at different growth stages, where an ample dose of nutrients enhanced the LAI over the control (T12, no fertilizer); although, an improvement in the LAI did not differ significantly in all the growth stages in both years (Table 5). The LAI value of rice gradually increased for the *Kharif* and *Boro* rice during both the years for all treatments and reached its maximum values at 60 DAT, followed by a decline as the crops reached maturity. In the case of *Kharif* rice, the maximum LAI was noted at 60 DAT with T1 and it was statistically on par with all treatments in 2014 and 2015. Similar to *Kharif* rice, the LAI of *Boro* rice at different growth stages in both years also did not differ significantly for all treatments. Among these treatments, the higher value of LAI was recorded in the T1 treatment and the minimum LAI value was in the control plots; although, the LAI for all treatments did not differ significantly. Considering the growth stages, the higher LAI was observed at 60 DAT in both years and the minimum value was at 100 DAT (Table 5). The application of the recommended dose of nutrients produced a higher LAI value, due to the proper nutrition in the plant helping it attaining sufficient vegetative growth (LAI) and keeping the crop healthy irrespective of growth stages and year. This assumption was also confirmed by several earlier studies [34,35], who also revealed an increase in LAI with the recommended dose of N:P:K:Zn:S.

The number of tillers m−<sup>2</sup> of *Kharif* and *Boro* rice was also influenced by nutrient management, observed during two consecutive years (Table 6). Application of an ample dose of nutrients, i.e., N80P40K40Zn25S20 in *Kharif* rice and N120P60K60Zn25S20 in *Boro* rice, resulted in the production of the maximum number of tillers over the control at all the growth stages. Considering the growth stages, tillers m−<sup>2</sup> of the *Kharif* rice at 20 DAT were significant in both years, and 40 and 60 DAT only for all treatments; although, the maximum tillers m−<sup>2</sup> was recorded in T1 and the lowest was in the T12 (control) treatment. With little exception, tillers m−<sup>2</sup> for T1 was statistically on par with T2, T4, T6, T8, and T10 in increasing the number of tillers during both years; however, T1 significantly produced more tillers than T3, T5, T7, T9, T11, and T12 (control).


 stages.

different letters within the continuous columns indicate significant differences at the 1% level of probability.


**Table 5.** Effect of nutrient management on the leaf area index of rice at different growth

 stages.


 stages.

*Plants* **2021** , *10*, 1622

different letters within the continuous columns indicate significant differences at the 1% level of probability.

A similar trend was also noted in *Boro* rice, where an ample dose of recommended nutrients (T1) produced maximum tillers per unit area. Treatment T1 showed its significant superiority to T3, T5, T7, T9, T11, and the control (T12, no fertilizer) during both years, but T1 remained statistically on par with T2, T4, T6, T8, and T10. Omission of all nutrients in T12 was totally dependent on inherent soil fertility and, due to lack of sufficient nutrients, it did not produce the desired number of tillers. On the other hand, the treatment T1 received an ample dose of recommended nutrients that facilitated proper nutrition and resulted in maximum tillers per unit area at different growth stages of *Kharif* and *Boro* rice during both the years of study. The beneficial effects of fertilizers in enhancing tillers were earlier observed by researchers [36,37].

#### *3.2. Yield Attributes and Yield*

Yield attributes such as panicles m−2, grains panicle−1, spikelets panicle−1, test weight, and panicle length were recorded for both *Kharif* and *Boro* rice during both seasons (Table 7). Considering both seasons data of these parameters, panicles m−2, grains panicle<sup>−</sup>1, spikelets panicle−1, and test weight varied significantly only in the first season. The recommended dose of nutrients (T1) registered higher values than T3, T5, T7, T9, T11, and T12 (control) in both years. However, the treatment with an ample dose of nutrients (T1) was statistically on par in increasing the values of the yield attributes.

The yield-attributing characters of *Boro* rice did not differ significantly in both years, where T1 exerted higher values over T3, T5, T7, T9, T11, and the control (T12, no fertilizer) during 2014–2015 and 2015–2016. However, T1 was statistically on par with the T2, T4, T6, T8, and T10 treatments. The results corroborate the findings of earlier studies [34,35], where researchers revealed that balanced doses of all nutrients influence the proper growth and development of plants, leading to improved yield-attributing characters of rice.

The 'R' values of the yield attributes were reflected in the productivity of the *Kharif* and *Boro* rice in terms of grain and straw yields during both the years of study (Figures 2–7). The data showed that the grain yield of *Kharif* rice was at its maximum (5.46 and 5.67 t ha−<sup>1</sup> in 2014 and 2015, respectively) with the treatment T1 (Figure 8). In 2014, the treatment with an ample dose of nutrients (T1) produced significantly more grain yield than T2, T3, and the control (T12); but, in 2015, T1 yielded significantly more than T3 and the control. The other treatments were statistically on par with T1. The grain yield of *Boro* rice was higher with the application of an ample dose of the recommended fertilizer (T1) that yielded 6.6 t ha−<sup>1</sup> in both years. The treatments were statistically on par with the other treatments, except for T2, T3, and T12 (unfertilized control), in increasing the grain yield of *Boro* rice during both years. In the rice–rice cropping system also, both the *Kharif* and *Boro* rice yielded more with the ample dose of nutrients application. A similar type of impact of an ample dose of recommended nutrients was earlier noted by Mohapatra [38] and Trivedi et al. [39].

