Indigenous Nutrient Supplying Capacity of Vertisols under Cotton and Soybean

The current project was initiated to characterize and assess the fertility status of soils in intensive cotton and soybean growing areas of Maharashtra using nutrient omission plots, and to assess the spatial and temporal variability of these nutrient responses. Fifteen on-farm nutrient omission trials on cotton and soybean were conducted in farmers’ fields in Akola District. The trials compared four treatments: 1) ample NPK and other limiting nutrient application, 2) omission of N from the ample treatment, 3) omission of P from the ample treatment, and 4) omission of K from the ample treatment. Soybean was grown under rainfed conditions, while cotton was grown under both rainfed as well as with supplementary irrigation.

Cotton was planted in 2013 and harvested in 2014. The yield of seed cotton varied from 2.2 t/ha with no N application to 2.7 t/ha with full NPK application. Lowest seed cotton yield was recorded with omission of N at all sites. The yield-attributing characters and nutrient uptake was highest with the ample NPK treatment. The yield-attributing characters in cotton revealed that the number of bolls was significantly higher under ample NPK, while they were lowest with omission of N. The number of bolls opened during first picking were significantly lower under omission of K. The average boll weight was lowest with the omission of N. The fiber properties of cotton were not influenced significantly due to various treatments under study. The nutrient use efficiency (kg seed cotton per kg nutrient applied) of N, P and K was lowest due to no P application in cotton. The nutrient use efficiency of N, P and K was found most sensitive to P followed by K and N application in cotton.

The soybean planted in rainy season of 2014 showed that ample NPK application produced 1.8 t/ha of grain yield. The soybean yield obtained in 2014 with ample NPK was lower than the previous year due to an erratic monsoon. Omission of N, P and K from the fertilization schedule reduced soybean yield by 330, 400 and 140 kg/ha as compared to the ample treatment. The nutrient use efficiency (kg grain per kg nutrient applied) of N, P and K was lowest due to no K application in soybean. The nutrient use efficiency of N, P and K was found most sensitive to K followed by N and P application in soybean.