Nutrient Use Efficiency and Productivity of Field Pea (Pisum sativum L.) Influenced by Combined Nitrogen and Sulphur Application 

The demand for pulses in India will increase with a growing population as well as sustained economic growth (Raja et al., 2017). Field pea (Pisum sativum L.) is a major crop of grain legumes for human and animal feeding. The crop is a major protein source with high levels of high nutritional value amino acids, lysine and tryptophan (Bhat et al., 2013). Field pea is one of important rabi pulse crop grown in Kashmir valley. The adequate supply of macro and micro nutrients is necessary for plant growth and to get optimal yield. The S and N plays vital part in the synthesis of proteins, thus these nutrients in plants are highly inter-related. Sulphur deficiency in crops has become widespread (Scherer, 2001) due to intensive cropping and use of sulphur free nitrogenous and phosphate fertilizer. Sulphur requirement is about 8kg per tonne of legume seed. Fazili et al., (2008) stated that deficiency of S limits the efficiency of added N, consequently, S addition becomes essential to improve the efficiency of applied nitrogenous fertilizer. Nitrogen always results in low N use efficiency and serious N losses (Ma et al., 2010) and consequently leads to pollution of surface water, groundwater and the atmosphere (Liu et al., 2005). In order to increase the nitrogen use efficiency and to reduce the rate of nitrogen application the current investigation was undertaken to study of the response of field peas (Pisum sativum L.) to combined sulphur and nitrogen fertilization.

The experiment was conducted at Agronomy farm of Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Faculty of Agriculture, Wadura during rabi 2016-17 and 2017-18 under rainfed conditions. The experimental site falls in temperate zone of North Western Himalayas. The soil was sandy loam in texture having neutral pH, organic carbon 1.82%, 208 kg/ha of available nitrogen, 12.8 kg/ha available P, 297 kg exchangeable K and 13.8 kg available S at the start of study. The experiment was laid out in factorial RBD with three levels of nitrogen (0, 15, 30 kg/ha) and four levels of sulphur (0, 15, 30, 45 kg/ha) with three replications. Field pea variety Shalimar Pea-1 was sown with row to row spacing of 30 cm. During both the years, the crop was sown on 2^nd week of October and harvested at physiological maturity. The urea and gypsum were the source used for nitrogen and sulphur respectively. Total quantity of nitrogen, phosphorous and potassium was applied as per the treatments just before sowing. Nodule count was done at start of flowering, for this reason 6 randomly selected plants from each plot were uprooted. The nutrient use efficiency was calculated as given by Dobermann (2007).           
                 
Y   = Yield from fertilized plot (kg/ha).
Y0 = Yield from unfertilized plot (kg/ha).
F = Quantity of fertilizer (N+S) applied (kg/ha).
 
The equivalent energy values (Table 1) of various inputs and outputs as suggested by Saad et al., (2016) and Devasenapathy et al., (2009) were used for computing total energy input and energy output of field pea.
 

 

Number of root nodules per plant
 
The data in Table 2 revealed that number of nodules per plant showed positive relationship with increased sulphur levels and negative relationship with increased nitrogen levels. However the significantly higher nodule count per plant was recorded with application of 30 kg S/ha without nitrogen. Further increase in sulphur had not significantly increased number of nodule per plant. Higher number nodules per at higher levels of sulphur were also reported by Chandra and Khaldelwal (2009) in chickpea and Munshi et al., (2001) in groundnut.
 

 
Yield contributing characters
 
During 2016, the application of 30 kg N/ha have recorded significantly higher yield attributing characters (number of seeds per plant and 100 seed weight) of field pea than no application of nitrogen, however was statistically at par to 15kg N/ha application (Table 3). Similar trend was observed during 2017. Higher yield contributing characters  observed at 30 kg N/ha could be due to greater partitioning of dry matter into the economic portion i.e., to seed and favourable growth nutrient uptake. This was evident by the consistent results exhibited by application of nitrogen in both the seasons. Low pod yield recorded under control plots during the study could be due to insufficient essential element (nitrogen) at early growth stages. Nannim et al., (2018) also found higher seed yield of field pea with the higher application of nitrogen. Similar results were also reported by Sinclair (2004).
 

        
Sulphur application also registered significantly higher yield contributing characters of field pea upto to 30 kg S/ha (Table 3). However further increase in sulphur level (45 kg/ha) had not significantly increased yield contributing characters. Similarly the levels of sulphur up to 40 kg/ha showed linear increase the growth, yield attributes, seed and stalk yield of chickpea (Nawange et al., 2011).
 
Seed yield
 
The seed yield increased with increase in sulphur and nitrogen levels during both year of study (Table 4). However significantly higher seed yield was recorded with application of 30 kg S/ha and 15 kg N/ha. Further increases in sulphur and nitrogen levels had not registered significant increase in seed yield of field pea. This may be attributed to higher number of nodules/ plant, seed/plant and 100 seed weight with higher levels of sulphur application and higher number of yield contributing characters with higher levels of nitrogen. Similar results were also reported by Nawange et al., (2011) in chickpea, Jamal et al., (2005; 2006) in soybean and Rao et al., (2001).
 

 
Nutrient use efficiency
 
The nutrient use efficiency was significantly influenced with application of varied rates of nitrogen and sulphur fertilizer. The response (kg grain increase/kg nutrient applied) of field pea was maximum (21.53 and 20.69) with combined nitrogen (15 kg/ha) and sulphur (30 kg/ha) application in both years compared to other treatments (Table 5). Similar findings were also reported by Fazili et al., (2008). While the lowest response (11.6 and 8.6) was recorded with application of 15 kg sulphur alone in both years. Similar findings in rice-wheat cropping system were also reported by Singh et al., 2017.
 

 
Energy use efficiency
 
Energy consumed, net energy return and energy productivity with different rates of nitrogen and sulphur fertilisation is depicted in Table 6. Higher energy was consumed with application higher rates of sulphur and nitrogen. Similar trend was recorded related to output energy. The net energy return was found higher with application of 15 kg N/ha and 30 kg S/ha compared to other treatments. Ramesh et al., 2018 also found variation in energy input and out put energy with different levels of fertilizer application in maize based cropping system. Lowest energy productivity (kg/MJ) was recorded with no application of nitrogen and sulphur fertilizer, followed by combined application of 15 kg N/ha and 30kg S/ha compared to other treatments. Variation in input energy and output energy with different nitrogen rates in maize-wheat cropping system was also depicted by Khokhar et al., (2017).
 

 
Economics
 
Combined application of 15 kg N/ha with 30 kg S/ha recorded higher mean benefit cost ratio (3.94) compared to other treatment combination (Table 7). Higher B:C may be attributed higher grain yield than N₀S₁, N₀S₂, N₀S₃, N₁S₀, N₁S₁ ­, N₂S₀ N₂S₁­ (Table 4) and lower cost of cultivation than N₁S₃, N₂S₂, N₂S₃. Nina et al., (2021) also found that combined use of nitrogen with sulphur reduced the nitrogen surplus in cabbage and was economical viable.
 

Based on the results a significant interaction was found between sulphur and nitrogen in terms of number of nodules per plant, seed yield and nutrient use efficiency in field pea. The combined application of nitrogen (15 kg/ha) and sulphur (30 kg/ha) was economically viable and also have lower energy consumption. The existing recommended starter dose of nitrogen in field pea is 30 kg/ha in Kashmir valley. From the findings of present study (30 kg S/ha and 15 kg N/ha) the farmer can save 50% of starter dose of nitrogen in field pea. Further, the reduced application of nitrogenous fertilizer will reduces losses of different forms of nitrogen to surface water, groundwater and to the atmosphere. Hence, to save the environment and to get higher productivity of field pea, it is recommended to apply 30 kg of sulphur and 15 kg N/ha in Kashmir Valley.