PhD

A study on “Assessment and management of micronutrient deficiencies in Onattukara” was undertaken with an objective to assess the available micronutrient status of the Onattukara region to develop a multi micronutrient mixture for balanced crop nutrition and to evaluate the effect of multi micronutrient mixture on growth and yield of okra. Two hundred georeferenced soil samples were drawn at random from twenty soil series of the Onattukara region representing different crop production systems and analysed for 13 soil fertility parameters. The results of the analysis of various soil parameters were integrated in GIS for the preparation of thematic maps. The overall fertility status of this region indicated that the soil was very strongly acidic with high level of phosphorus, low oxidisable organic carbon and available potassium and wide spread deficiencies of calcium, magnesium, boron and zinc. Observational trials were conducted at 18 different locations to assess the response of the okra crop to adhoc recommendations by KAU for micronutrients. Micronutrient application increased the yield up to eighty percent in these trials.
Micronutrient fertilizer requirement was computed based on the available micronutrient status of the region and crop requirement. A multi micronutrient mixture having a composition of Zn (9.5%) + B (2.6%) +Cu (1.2%) +Mg (2.4%) +N (0.46%) @ 20kg ha-1 was developed and the effect of multi micronutrient mixture was assessed in the field experiments using okra variety Varsha Uphar as the test crop in two seasons during September- December in 2013 and February -May in 2014. The field experiment consisted of nine treatments and the treatments were T1 (Absolute control), T2 (Package of Practices (POP) ), T3 (Soil test based POP and secondary nutrients), T4 (Treatment 3 + computed dose of micronutrients mixture), T5 (Treatment 3 + 25% less of computed dose of micronutrients mixture),T6 (Treatment 3+ 25% more of computed dose of micronutrients mixture), T7 (Treatment 3+ foliar application of 0.5% solution of computed dose of micronutrients mixture), T8 (Treatment 3+ foliar application of 0.5% solution of 25% less of
computed dose of micronutrients mixture) and T9 (Treatment 3 + foliar application of 0.5% solution of 25% more of computed dose of micronutrients mixture).
Growth, yield and quality of okra increased significantly due to multi micronutrient mixture. Application of soil test based NPK and secondary nutrients + foliar application of 0.5 per cent solution of computed dose of micronutrient mixture @ 5 kg ha-1 in two splits at 15 DAS and 35 DAS (T7) yielded significantly higher (11.3 tha-1) over rest of the treatments. T7 recorded 80 per cent more yield than T3, which was the soil test based package of practices (POP) and secondary nutrients and more than double the yield of POP. Soil application of this mixture @ 20kg ha-1 (T4) was also significantly superior to the POP recommendations.
Soil status of micronutrients in the experiment site before the experiment was Zn (0.27 mg kg-1), Cu (0.21 mg kg-1) and B (0.17 mg kg-1). After two consecutive application of multi micronutrient mixture, the soil status of Zn, Cu and B were in the range of 0.62 to 1.58 mg kg-1, 0.74 to 0.99 mg kg-1 and 0.19 to 0.31 mg kg-1 respectively. Even after continuous application of micronutrients for two seasons the critical status was not attained for Cu and B in soil. So application of micronutrient fertilizers customized for agro ecological units and crops ensures increased yield and sustain soil health. In general the highest nutrient content and uptake in shoot and fruit were recorded by T7. The highest B: C ratio of 3.02 was also recorded by T7. From the investigation it can be concluded that foliar application of micronutrient mixture @ 5kg ha-1 in two splits at 15 DAS and 35 DAS was superior to soil application with respect to yield, quality and B: C ratio. The study revealed that micronutrient deficiency is one of the yield barriers which can be broken down by including micronutrient fertilizers in the nutrient schedule of crops.