Assessing the indigenous nutrient supplying capacity of soils to Soybean in Vertisols of Northern Karnataka
A study was undertaken in the farmer fields growing soybean in Northern Karnataka with the following objectives 1. To assess the fertility status of soils in soybean growing areas of Northern Karnataka and to study the response of soybean to major nutrients and response variability across spatial and temporal scale. 2. To study the nutrient uptake pattern, nutrient use efficiency and residual soil fertility through nutrient omission technique. 3. To create awareness among farmers for optimized nutrient use and best nutrient management practices for soybean
IPNI-2014-IND-531
29 Apr 2016
2015 Annual Interpretive Summary
The current investigations were undertaken to determine the soybean yield response to applied nutrients in Vertisols of northern Karnataka. Replicated on-station experiments were conducted at a) Agricultural Research Station (ARS), Dharwad farm and b) Main Agricultural Research Station (MARS) in the University of Agricultural Sciences, Dharwad. The study consisted of six treatments; one with ample NPK (30-100-80 kg N-P2O5-K2O/ha); three treatments with omission of N, P and K from the ample NPK; State Recommendation/RDF (40-80-25 kg/ha), and an absolute unfertilized control. Deficient secondary and micronutrients were applied to all the five treatments based on the soil test results. Soybean variety JS-9305 was sown during the first week of June 2015 and prior to sowing, the seeds were treated with specified Rhizobium culture.
At ARS Dharwad, the growth and yield observations due to omission of major nutrients revealed that the grain yield of soybean in ample NPK treatment was 2,050 kg/ha and yield response to application of N, P and K was 410, 340 and 200 kg/ha, respectively. The yield reduction due to omission of N, P and K was 20, 16.6 and 9.6%, indicating that N followed by P are the most limiting nutrients for growing soybean on these medium deep black soils. The yield recorded for the RDF and absolute control were 1,890 and 1,430 kg/ha, which were 8 and 30% lower than the ample NPK treatment. The higher grain yield of soybean in ample NPK treatment was attributed to significantly high dry matter per plant, more number of pods per plant, high test weight of seed and taller plant height, whereas the relationship between grain yield and number of nodules per plant was non-significant.
Similar results were measured at MARS Dharwad, a grain yield of 2,200 kg/ha was recorded in the ample NPK treatment, which was higher than the omission of N, P, K, RDF, and absolute control by 37, 22, 6, 3, and 42%, respectively. Grain yield difference between ample NPK and RDF and ample NPK and K omission was statistically non-significant. The high yield of soybean in the ample NPK treatment was attributed to significant growth observations in terms of plant height, number of pods per plant and 100-seed weight.
The above information will be used in the development of fertilizer decision support tool for soybean and help in providing better fertilizer recommendations to soybean-growing farmers.