Indigenous Nutrient Supplying Capacity of Vertisols under Cotton and Soybean

The current project was initiated to compare the Nutrient Expert®-Soybean (NE)-based fertilizer recommendation with the existing official fertilizer recommendation (SR) and farmers' fertilizer practice (FFP). Fifteen on-farm and one on-station soybean experiments were conducted in the Akola District of Maharashtra. Soybean variety JS-335 was grown under rain-fed conditions across all the experimental sites. The study was also aimed to characterize and assess the fertility status of soils in intensive cotton-growing areas of Maharashtra and determine the yield response of cotton while assessing the spatial and temporal variability of these nutrient responses.

Comparison of fertilizer nutrient use in soybean between NE and FFP revealed that N, P₂O₅, and K₂O fertilizer use in FFP varied from 11 to 60, 19 to 73, and 0 to 51 kg/ha, respectively, with respective averages of 32, 39, and 19 kg/ha. The corresponding NPK use based on NE recommendations varied from 20 to 27, 20 to 59, and 19 to 57 kg/ha, with averages of 25, 45, and 44 kg/ha. The NE-based fertilizer recommendation reduced the N application rate by 7 kg/ha, while increasing P₂O₅, and K₂O use by 6 and 25 kg/ha, respectively. Data on mean grain yield of soybean with NE was 2.5 t/ha, which was 6% higher than FFP (2.4 t/ha). A similar on-station replicated study conducted at the research farm of Dr. PDKV, Akola reported a grain yield of 3.4 t/ha with NE, which was 9% higher than SR (3.2 t/ha) and 18% higher than FFP (2.9 t/ha), respectively. The study also showed that omission of N, P, and K from the NE-based recommendation reduced soybean yield by 460, 630, and 280 kg/ha, indicating that P is primarily responsible for limiting soybean yield followed by N and K, respectively.

In cotton, the seed cotton yield was highest (2.4 t/ha) in the ample NPK treatment, followed by P omission treatment. The highest reduction (19%) in the seed cotton yield was recorded in the N omission treatment, while K omission resulted in a 13% yield reduction, indicating that cotton productivity is most sensitive to N, followed by K. Post-harvest soil analysis and nutrient uptake assessment is in progress. The data will be used to develop a site-specific nutrient recommendation tool for cotton similar to Nutrient Expert developed for major cereals and soybean.