High variation in pod yield of groundnut was observed in winter planted irrigated peanut, depending on the time of planting. A field experiment was conducted with different dates of planting starting from beginning of the winter until end of the winter at 15 d intervals. Crop developmental stages were divided into three stages: vegetative, reproductive, and maturity. Weather parameters like maximum temperature, morning and evening relative humidity, sunshine hours, and evaporation were recorded from the observatory adjacent to the experimental field. Simple correlations and step down regression analyses were carried out between weather parameters in development phase and fruit attributes, pod yield, and harvest index. The results revealed that fruit attributes like hundred kernel weight, shelling percentage, and harvest index were significantly and negatively correlated with minimum temperature which prevailed over pod filling phase, accounting for 83.0, 94.8, and 82.8% variations respectively (R 2 5 0.830, 0.948, and 0.828), while haulm yield was significantly and positively correlated with minimum temperature which prevailed during pod filling phase, accounting for 82.1% variation in haulm yield (R 2 5 0.821). Pod growth rate and pod yield were significantly and positively correlated with diurnal variation in temperature, accounting for 63.5 and 69.0% variations respectively (R 2 5 0.635 and 0.690). The relationship between weather parameters, fruit attributes, and pod yield was established through a set of regression equations.
Key words Available soil moisture Can evaporimeter Cumulative can evaporation High frequency irrigation Scheduling irrigation Uptake of nutrientsSummary Field experiments were conducted during 1979 and 1980 summer seasons on sandy loam soils of low moisture retentive capacity to study the effect of high frequency irrigation at different levels of N on groundnut yield and nutrient uptake (NPK).Four irrigation frequencies (irrigation at 2, 4, 6 and 8cm cumulative can evaporation, corresponding to irrigation once in 3, 5, 7 and 10 days respectively) and four levels of nitrogen (0, 20, 40 and 60 kg N/ha) were tested in a factorial randomized block design with three replications.Pod yield of groundnut was maximum (3,293 kg/ha) when irrigations were scheduled at 4 cm cumulative can evaporation (once in 5 days). Addition of N did not increase the pod yield. N and P uptake by the crop was maximum (180kg N and 18 kg P/ha) with high frequency irrigation of scheduling irrigation at 4 cm cumulative can evaporation. Highest uptake of N (183 kg/ha) and P (19 kg/ha) was with a combination of 20 kg N/ha and high frequency irrigation (4 cm CCE). K uptake was low with low irrigation frequency, while it was highest (67 kg K/ha) at 20 kg N/ha.
When water supplies are restricted, so that full evapotranspiration demands cannot be met, limited irrigation is practised. Management strategy of limited irrigation is to optimise production per unit of applied water rather than to maximise yield per unit of land. Principles that help to facilitate limited irrigation strategies can be broadly grouped into three: agricultural water management, crop considerations and agronomic options. When anticipating low water year, choose crops which maximise production with limited water. In decreasing order of efficiency, short season indeterminate and long season indeterminate crops should be chosen judiciously. Deficit irrigation practices, localised irrigation methods, reducing water losses,conjunctive use of water resources etc can help minimise yield losses due to soil moisture stress. Additional agronomic management options that can maximise production include conservation tillage, advancing or delaying planting dates in order to coincide the crop’s critical period with water availability, decreasing plant competition byreducing seeding density and controlling weeds. Available options to address the challenge of limited irrigation have been briefly presented.
Summary Three levels of irrigation, three plant densities and three fertiliser schedules were tested in 33 factorial confounded design with two replications in winter on sandy loam soils of Tirupati campus of Andhra Pradesh Agricultural University.Pod yield did not vary due to the plant densities and the fertiliser schedules when the crop was sown in optimum time during 1980. When the sowings were delayed, as in 1979, 444000 plants per ha and 60kg N ha -~ , 40kg P ha -~ and 100kg K ha -~ was optimum. Scheduling irrigation at 25 or 50% DASM (depletion of available soil moisture) was optimum for the groundnut crop.There was no difference in the uptake of NPK due to irrigations at 25 and 50% DASM in both the years. Low plant density was as effective as high plant density for efficient use of fertilisers. Uptake of NPK by the crop was relatively high at higher fertiliser levels. However, this higher uptake did not contribute to high pod yield, probably due to utilisation of absorbed nutrients for rank vegetative growth.
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