Response of integrated nitrogen management on nutrient content-uptake and economics in kharif sorghum

Introduction

Amongst cereals, sorghum is the fourth most important crop after rice, wheat and maize. Sorghum [Sorghum bicolor (L.) Moench], the king of millets holds promise for food, feed, fodder and ration for human, cattle and poultry. In India, it is popularly known as "Jowar". Its grains have about 10-12% protein, 3% fat and 70% carbohydrate. The sorghum crop exhausts more nutrients than other forage crops and being cereal crop, requires higher amount of nutrients for higher productivity. Among the various agronomic factors determining crop productivity, adequate and prudent use of fertilizer is considered the most important to achieve potential and targeted crop production. However, ill effects of chemical fertilizers on soil health, energy crisis, and prohibitive cost of chemical fertilizers and poor purchasing power of small and marginal farmers restrict the use of this vital input. Therefore, it is time to develop a strategy for integrated use of organic manures in conjunction with chemical fertilizer to the maximum possible extent with proper technology to boost crop production. Among the essential nutrients, nitrogen is universally deficient in Indian soils. Nitrogen is essential constituent of chlorophyll and implies dark green colour to the plants and an integral part of amino acids. It contributes to the building units of protein and growth of plants. It promotes shoot elongation, tillering and regeneration after defoliation and governs to considerable degree, the utilization of phosphorus, potassium and other elements in the plant. In plant nutrition, organic matter level of a soil is the key property that decides the availability status of essential nutrients. The role of organic materials in maintaining and increasing soil fertility is well established. Maintenance of optimal level of organic matter in soil is essential to sustain productivity. Although increase level of production can be achieved by increase the use of inorganic fertilizers alone but it may lead to pollution problem and deterioration in soil characteristics i.e. organic carbon and soil fertility. This can only be maintained at sustainable level by the application of organic manures. There is an increasing interest in the use of organic manures as a source of nutrient supply to crop production for sustainable soil productivity, ecological stability and to minimize the requirement of chemical fertilizers. Indian soils are poor in organic carbon due to its tropical climate. With the increasing soil degradation and cost of chemical fertilizers, there is a need to integrate them with organic sources, which are good for soil health besides supplying nutrients for longer period. The organic manures like FYM and castor shell compost are natural sources of slow release nutrients and inclusion in nutrient management has become necessity to improve the soil fertility and to sustain the productivity. Addition to these, it increases soil microbiological activities and plays key role in transformation, recycling and availability of nutrients to the crop. It also improves the physical properties like soil structure, porosity, reduces compaction and crusting and increases water holding capacity of the soil. Farmyard manure refers to the decomposed mixture of dung and urine of farm animals, litter and leftover material from roughages or fodder fed to the cattle. On average well decomposed farmyard manure contains 0.5% N, 0.2% P2O5 and 0.5% K2O. FYM increases the N-use efficiency of the crop and the status of organic carbon, available N, P and trace elements in the soil. FYM also improves the physical condition of the soil. The well decomposed castor shell compost contains 2.24% N, 0.82% P2O5, 1.74% K2O with pH 7.33 and EC 0.16 dS/m (Annual Report, 2020) [1] . Bio-fertilizers are cheaper, pollution free and renewable source of nutrients supply. Introduction of beneficial microorganisms into soil in a capacity of biofertilization could increases plant growth by providing nutrients in available forms. Azotobacter bacteria are free living non-photosynthetic aerobic N2-fixing bacteria which activate nitrogen cycle in the rhizosphere, and produce vitamins as thiamine and riboflavin and hormones as indole acetic acid, gibberellic acids and cytokinin's.

Materials and Methods

A field experiment was conducted at Agronomy Instructional Farm, Chimanbhai Patel College of Agriculture, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar during the kharif seasons of 2022 and 2023, entitled with "Response of integrated nitrogen management on nutrient content-uptake and economics in kharif sorghum". The experiment was laid out in a randomized block design comprising of 10 treatments viz., T1: absolute control, T2: RDF (80:40:00 kg N:P2O5:K2O/ha), T3: 25% RDN through FYM + 75% RDN through urea, T4: 50% RDN through FYM + 50% RDN through urea, T5: 25% RDN through castor shell compost + 75% RDN through urea, T6: 50% RDN through castor shell compost + 50% RDN through urea, T7: 25% RDN through FYM + 50% RDN through urea + Azotobacter, T8: 25% RDN through castor shell compost + 50% RDN through urea + Azotobacter, T9: 25% RDN through FYM + 25% RDN through castor shell compost + 50% RDN through urea, T10: 50% RDN through FYM + 50% RDN through castor shell compost + Azotobacter to sorghum replicated four times in a gross plot size of 6.0 m × 9.0 m. Sorghum crop variety 'GJ 43' was sown in June with recommended package of practices during both the years. Sowing of sorghum was done with recommended seed rate of 12 kg/ha by maintaining 45 cm distance between the rows. The application of fertilizer for sorghum was applied as per fertilizer treatment. According to content of nutrient, FYM and castor shell compost were applied to sorghum crop as per treatments at least 13 days before sowing and incorporated into the soil. Recommended dose of fertilizers (80: 40: 00: kg N: P2O5: K2O ha -1 ) were applied through urea and SSP as per the treatments. 25% inorganic N was applied at basal and remaining 75% as three equal splits at 20, 40 and 60 DAS. Seeds of sorghum were treated 10 ml Azotobacter per kg seed in specific treatments at the time of sowing. The 1 st irrigation was given immediately after sowing and remaining irrigations were given as per requirement of the crop. During the entire crop season experimental area was kept weed free and clean. Sorghum was harvested in the 1 st week of October during both the years. The (grain and fodder) samples of sorghum were subjected to analysis of N through Micro-Kjeldahl's method, P through calorimetrically Vanadomolybdic phosphoric acid yellow colour method, K through Flame photometric method (Jackson, 1973). The concentration of nutrients in grain and fodder were used to calculate the uptake of nutrients by sorghum crop. The uptake of nutrients by sorghum were worked out by using following formula.

Economics was worked out on the basis of prevailing market prices of inputs and output obtained from each treatment. The data collected from chemical study were subjected to statistical analysis and interpretation of data of various characters studied in present investigation as suggested by Panse and Sukhatme (1967). The critical difference (CD) at 5% was calculated where differences among the treatments were found significant in 'F' test. The co-efficient of variation percentage (C.V.%), illustration based on the data are given at appropriate places in respective table.

Results and Discussion

Effect on nutrient content Effect of applying different integrated nitrogen management treatments are shown in Table 2. A critical examination of data (Table 2) indicated that application of 50% RDN through castor shell compost + 50% RDN through urea (T6) to sorghum gave significantly higher nitrogen content in grain (1.679%) and fodder (0.855%) during pooled study, which was remained at par with treatments T9 (1.635%), T4 (1.630%), T5 (1.619%), T3 (1.605%) and T2 (1.604%) in pooled study of N content in grain. Higher content of nitrogen in castor shell compost promoted increase in available nitrogen in soil and improved soil structure due to increased organic matter that increased nutrients availability. The favorable conditions for microbial as well as chemical activities resulted in increased N content of grain and fodder. Incorporating organic sources along with chemical fertilizers resulted in the formation of clay-humus complexes in the soil which in turn promotes higher and prolonged availability of nitrogen to the crop Kumar et al. (2005) [5] , Singh et al. (2013) [8] , Yadav and Singh (2016) [11] , Rakesh (2017) [7] and Khushbu (2021) [4] . The mean data presented in Table 2 indicated that different treatments tried in the experiment showed that application of 50% RDN through castor shell compost + 50% RDN through urea (T6) to sorghum registered significantly higher phosphorus content in grain (0.341%) and fodder (0.218%) in pooled study. Treatment T6 was remained at par with T9 (0.333%) and T4 (0.326%) in pooled study of P content in grain. In case of phosphorus content in fodder T6 was remained at par with only T9 (0.209%). This could be attributed to the fact that added castor shell compost increased the phosphorus concentration in grain and fodder due to better root establishment into rhizosphere, resulting in higher absorption of phosphorus due to supply more plant available P as well mobilizes native soil P and converted into plant available form and sustain in increased growth led to higher content of P. Increased accumulation of nutrients especially N and P in vegetative plant parts concomitant with improved metabolism led to greater translocation of N and P in reproductive structure led to higher concentration. These results are in close proximity with the findings Kumar et al. (2005) [5] , Singh et al. (2013) [8] , Yadav and Singh (2016) [11] , Rakesh (2017) [7] and Khushbu (2021) [4] . An examination of data (Table 2) indicated that the different treatments tried in the experiment did not exert any significant effect on the potassium content in fodder in pooled study. A perusal of data indicated that the application of 50% RDN through castor shell compost + 50% RDN through urea (T6) to sorghum registered significantly higher potassium content in grain (0.614%) in pooled study. Treatment T6 was remained at par with T4 (0.610%), T5 (0.610%), T9 (0.608%), T2 (0.605%), T3 (0.596) and T10 (0.585%) in pooled study of potassium content in grain.

A scrutiny of data (Table 3) revealed that application of 50% RDN through castor shell compost + 50% RDN through urea (T6) show significantly higher N uptake by grain (36.36 kg/ha) and fodder (120.14 kg/ha) of sorghum crop during pooled analysis and remained statistically at par with treatment T9 (34.04 kg/ha) and T4 (33.32 kg/ha) during pooled study in nitrogen uptake by grain. While treatment T6 remained statistically at par with treatment T9 (110.39 kg/ha) in nitrogen uptake by fodder. It can be inferred from the data that significantly higher P uptake (7.40 and 30.60 kg/ha in grain and fodder, respectively) by sorghum crop recorded under the application of 50% RDN through castor shell compost + 50% RDN through urea in pooled study and it was remained at par with treatments T9 (6.96 kg/ha) and T4 (6.67 kg/ha) in phosphorus uptake by grain. In case of P uptake by fodder treatment T6 remained statistically at par with only treatment T9 (28.42 kg/ha). A perusal of data indicated that significantly higher K uptake by grain (13.26 kg/ha) and fodder (188.15 kg/ha) of sorghum were registered under the treatment of (T6) 50% RDN through castor shell compost + 50% RDN through urea in pooled study, which remained at par with treatments T9 (12.68 kg/ha), T4 (12.47 kg/ha) and T5 (12.33 kg/ha) in K uptake by grain. In case of K uptake by fodder treatment T6 remained statistically at par with T9 (179.57 kg/ha), T4 (177.89kg/ha), T5 (175.57kg/ha), T3 (172.90 kg/ha) and T2 (169.75kg/ha). The maximum N, P and K uptake by grain and fodder of sorghum might be due to fact that castor shell compost release nutrients easily and furthermore, because of prolonged availability of moisture due to castor shell compost might be resulted into increased uptake of nutrients and also dry matter accumulation and higher yield recorded with application of castor shell compost which directly related with the higher uptake of nutrients observed by sorghum. This was in concomitant with the findings of Kumar et al. (2005) [5] , Vidyavathi et al. (2012) [10] , Singh et al. (2013) [8] , Yadav and Singh (2016) [11] and Khushbu ( 2021) [4] . The organic acids produced from decomposition of organic matter might be responsible for quick release of nutrients from native pool, result in greater availability on nutrients to growing plants and increase nutrient uptake by crop. The results are in line with those reported in the Castor Annual Report, 2020 [1] .

Economics

Among the different integrated nitrogen management treatments in Table 4, 50% RDN through castor shell compost + 50% RDN through urea (T6) recorded the maximum net (₹101472/ha) realizations but BCR (4.79) was fetched under treatment T2 RDF (80:40:00 kg N:P2O5:K2O/ha), which was closely followed by the treatment T2 for net (₹96848/ha) realizations and treatment T6 for BCR (4.00) and the minimum net realization (52947₹/ha) was procured with the treatment T1 (absolute control) and the lower BCR (2.39) recorded under treatment T10 (50% RDN through FYM + 50% RDN through castor shell compost + Azotobacter). This indicated that us e of 50% RDN through castor shell compost + 50% RDN through urea found more remunerative with respect to net return and BCR as compared to rest of the treatments. This could be attributed due to higher grain and fodder yield of sorghum received in these treatments. These findings are in accordance with those reported by Tudu et al. (2023) [9] and Javiya (2019) [3] .

Conclusion

Based on the findings of two years of experimentation, it is concluded that for securing higher grain and fodder yield, nutrient content-uptake and net profit from kharif sorghum crop under integrated nitrogen management, apply 50% RDN through castor shell compost + 50% RDN through urea to sorghum,