Yield prediction in cashew based on foliar nutrient levels
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Date
1990
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Department of Soil Science and Agricultural Chemistry,College of Horticulture, Vellanikkara
Abstract
A study was undertaken during 1988-90 with cashew plants of -variety BLA-39-4 of the NPK fertilizer trial of the Kerala Agricultural Development Project at Madakkathara, Thrissur to standardise foliar diagnostic technique for cashew in relation to nitrogen phosphorus and potassium content of the leaf and to predict the yield based on leaf nutrient levels. The experiment was laid out in 3 factorial randomised block design consisting of three levels each of nitrogen (250, 500 and 1000 g N/plant/year) phosphorus (125,250 and 500 g P2O5 /p la n t/y e a r) and potassium (250, 500 and 1000g K20 /plant/year).
For the standardisation of leaf position and period of sampling for diagnostic purpose, the leaves were serially numbered selecting the last fully matured leaf which was not having an inflorescence in the leaf axil as leaf N o.l. Before flushing and flowering of the shoots the leaves were grouped into three, viz ., top leaves, middle leaves and basal leaves. After flushing and flowering, the leaves at different leaf positions were grouped into four groups each consisting of two leaves; they^are group 1, group 2, group 3 and group 4. For the purpose of standardising the season best suited for- the collection of leaf intended for foliar diagnosis, samples were colleci ted at different stages of plantg rowth. The stages of sampling were : (1) Preflushing stage (2) After flushing but before flower opening (3) After the beginning of flower opening (4) After the opening of all the flowers of a panicle (5) At immature nut stage (6) At the time of harvest; and (7) Two months after harvest. Attempts were also made to establish the critical levels of N, P and K in leaf and to predict yield based on the regression model worked out.
Observations revealed that the N content in the leaf varied from 1.24 to 2.76 per cent. Pattern of variation in the content of N in the leaf at different stages of sampling followed a regular pattern. Prior to flushing, the content of N in the leaf was very low and it increased during the next two stages and thereafter the N content in the leaf declined. The distributions of N in the leaf at different leaf positions at different stages of sampling were rather inconsistent. The P content in the leaf varied from 0.063 to 0.316 per cent when all the leaf positions and stages of samplings were considered. Phosphorus content in the leaves was very low before flushing. With flushing the P content in the leaves increased upto the third stage of sampling and thereafter decreased. Potassium per cent in the leaf varied from 0.54 to 2.74 per' cent when all the leaf positions and stages of sampling were considered. Similar to 'N and P, the K content in the leaves at different stages of sampling also followed a regular pattern with the advancement of stages of sampling.’ Maximum K was noted in the younger leaves collected during the fourth stage of sampling. During this stage, leaf was sensitive to levels of applied K. The potassium per cent of the fruiting shoots decreased with increasing age of the leaf.
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