FERTIGATION STUDIES IN AEROBIC RICE – ZERO TILLAGE MAIZE CROPPING SYSTEM
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Date
2014
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
Abstract
A field experiment was carried out for two consecutive years (2011-12 and 2012-13) on a sandy loam soil of Regional Agricultural Research Station, Warangal with an objective to study the influence of irrigation schedules and nitrogen levels through fertigation in aerobic rice-zero tillage maize cropping system. The experiment was laid out in a split-plot design with four replications. Three irrigation schedules were taken as main plots and three nitrogen levels in sub plots in drip system for both rice and maize crops. Irrigation schedules for rice included I1: Drip irrigation (DI) at 100% pan evaporation (PE), I2: DI at 150% PE and I3: DI at 200% PE with nitrogen levels viz., N1: 90; N2: 120; and N3: 150 kg ha-1 through fertigation. For the subsequent maize crop, irrigation treatments included I1: DI at 75% PE, I2: DI at 100% PE and I3: DI at 125% PE with the three nitrogen levels i.e., N1: 120; N2: 160; and N3: 200 kg ha-1 in fertigation. Outside the layout of the main experiment, three checks and one check were tested in rice and maize crops, respectively. The checks for rice crop included, check 1: Aerobic rice nonirrigated with 120 kg N ha-1, check 2: Aerobic rice with supplemental irrigation at IW/CPE ratio of 1.5 with 120 kg N ha-1 and check 3: Puddled-flooded rice with 120 kg N ha-1. In maize crop, the check tested was surface irrigation at IW/CPE ratio of 1.2 with 160 kg N ha-1. The cultivars used for the study were ‘WGL 20471’ (Erramallelu) and ‘Pinnacle’ (private hybrid) in rice and maize crops, respectively during both the years.
Growth parameters, yield attributes, yield, nitrogen uptake, economics, water productivity and nitrogen use efficiency of aerobic rice and zero tillage maize were influenced by irrigation schedules and nitrogen levels through fertigation. During first year of study, leaf area index (LAI), SPAD chlorophyll meter reading and tillers m-2 of aerobic rice were significantly higher in 200% PE schedule compared to that of 100% PE but comparable with 150% PE. Drymatter accumulation at maturity, root volume and dry weight were more at 200% PE compared to that of lower schedules. The number of panicles m-2
and filled spikelets panicle-1 increased from 100% PE to 150% PE but not at 200% PE while sterility of spikelets was higher with 100% PE schedule. Higher grain and straw yield, nitrogen uptake, and economics were recorded with 200% PE over the other two schedules. Irrespective of the irrigation schedules, growth parameters (plant height, LAI, SPAD meter reading, tillers m-2 and drymatter accumulation), yield attributes (panicles m-2, panicle length and filled spikelets panicle-1) increased with level of N application from 90 to 120 kg N ha-1 while root volume and dry weight were higher at 150 kg N ha-1. The number of days taken to flowering was significantly lower with 150 kg N ha-1 while, sterility of spikelets was higher at 90 kg N ha-1compared to other doses. Grain yield, straw yield, nitrogen uptake and economic parameters were higher at 150 kg N ha-1. However, the maximum grain yield was recorded with puddled-flooded check followed by 200% PE schedule. Grain yield was reduced by 46 per cent in supplemental irrigated aerobic rice at 1.5 IW/CPE ratio compared to conventional flooded rice. The yield gap between aerobic and flooded rice was reduced to 17 per cent with drip irrigation at 200% PE. Considerable saving of water i.e., 75, 66 and 57 per cent was observed with 100% PE, 150% PE and 200% PE schedules, respectively over puddled-flooded check while it was 66 per cent with supplemental irrigated aerobic check.
In general, growth parameters (plant height, LAI, drymatter accumulation, root volume and root dry weight) yield attributes (cobs plant-1, kernels cob-1, kernel weight cob-1) kernel yield, stover yield and nitrogen uptake of no till maize increased with increase in water input from 75% PE to 100% PE irrigation schedule in drip irrigation but could not reach the level of significance at 125% PE. Tasseling and silking was hastened in 125% PE schedule. Increase in the level of N application from 120 to 160 kg N ha-1 resulted in the increase of all the growth parameters, yield attributes, kernel yield, stover yield and nitrogen uptake. Barrenness and test weight were unaffected by either the irrigation schedules or nitrogen levels. The economic indicators (gross returns, net returns and returns per rupee of investment) were higher with the irrigation schedule of 125% PE and nitrogen dose of 200 kg N ha-1 applied through fertigation.
Productivity of cropping system in terms of rice equivalent yield was the highest with the irrigation schedule of 200% PE and 125% PE and with the application of 150 and 200 kg N ha-1 to rice and maize crops respectively grown in the sequence. Water requirement increased with the increase in water input while its productivity reduced correspondingly in both rice and maize crops and the cropping system as a whole. However, nitrogen use efficiency enhanced with the increase in water input and reduced with increase in the N level. The investigations conducted for two consecutive years, clearly indicated the benefit of fertigation at 200% PE with 150 kg N ha-1 to rice and 100% PE with 160 kg N ha-1 to maize crops in increasing the productivity and profitability of aerobic rice - zero tillage maize cropping system.
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