Saturday, 15 July 2006
166-3

Effects of Long Term Fertilizer Application and Intensive Cropping on Dynamics of Soil Micronutrients under Tropical Agro Ecosystem.

Duraisamy Selvi1, Palaniappa Pillai Malarvizhi2, and Ponnusamy Santhy2. (1) Dept of Soil Science and Agricultural Chemistry, Tamil Nadu Agricultural Univ, Lawley Road, Coimbatore, 641003, India, (2) Dept of Soil Science,TNAU, Lawley Road, Coimbatore, 641003, India

The present investigation was undertaken in the on-going Long Term Fertilizer Experiment at Coimbatore, India with irrigated cropping sequence since 1972 inorder to find the nutrient management system which is more effective in nourishing the crops with adequate micronutrients. The experimental soil is calcareous, sandy clay loam with alkaline pH and EC 0.20 dSm-1. The ten treatments are: T1: 50% NPK; T2: 100% NPK (optimal); T3: 150% NPK; T4: 100% NPK with hand weeding (HW), T5: 100% NPK + ZnSO4 @ 25 kg ha- to maize alone; T6: 100% NP; T7: 100% N alone; T8: 100% NPK+FYM @10 tonnes ha-1 to finger millet alone; T9: 100% NPK (S free) and T10: Control. The available - Zn (2.58 mg kg-1) and Mn (2.74 mg kg-1) were in fair supply in soil but availability of Cu and Fe was insufficient to meet the crop needs. The analysis of surface soil samples after 31 years of intensive cultivation showed a steep decrease in DTPA – Zn except the continuous application of 100% NPK + ZnSO4 which resulted in 34 per cent build up and it continued to maintain the DTPA-Zn at a higher level of 3.48 ppm. The per cent depletion ranged from 63 to 88 and the rate of depletion was lower in 100% NPK+FYM. There was a build up in available Cu, Fe and Mn status irrespective of treatments including control and maximum in 100% NPK + FYM. Skipping of P lowers the micronutrient reserve and availability to a greater extent in soil. The cumulative uptake of micronutrients by the crops followed an order of Fe > Mn > Zn > Cu. The total Zn uptake of maize was the highest in 100 % NPK + ZnSO4 and FYM applied plots, the latter recorded the highest Fe, Cu and Mn uptake.


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