ALBERT

Description: SummaryExperiments made over a period of 3 years (1971–73) at Pantnagar, India, on the effect of plant density and spatial arrangement of a hybrid variety of maize (Ganga 2) and a local cultivar (Rudrapur) indicated that a density of (at least) 75000 plants/ha is necessary to obtain maximum grain yield. With increasing density from 25000 to 75000 plants/ha the date when 75 % of plants were silking was delayed 2–5 days and the percentage of barren plants increased from 1·7 to 28·7. In dense stands, grain yield of the hybrid variety was less affected by increasing row width from 60 to 90 cm than it was in the local cultivar.The average increase in yield with narrow (60 cm) row width as compared with wider (75 cm) row width was 6.8 % and it is argued that, in the context of the national need for increased food production, this increase cannot be overlooked.

Description: SUMMARYA laboratory incubation study followed by a field experiment was made in a silty clay loam soil (pH 6·9) at Pantnagar, India, on the effectiveness of ordinary urea, coated urea (sulphur and shellac-coated), urea-isobutyraldehyde condensation product (isobutylidenediurea, IBDU) and urea blended with nitrification inhibitor AM (2- amino-4 chloro-6-methylpyrimidine) and neem (a non-edible oil seed obtained from Azadirachta indica) cake. Whereas untreated urea and IBDU hydrolysed rapidly leaving no trace of urea-N after 2 weeks, sulphur-coated urea mineralized quite slowly and retained urea-N for as long as 4 weeks after incubation. Urea blended with neem cake was intermediate. Of all the materials tested, sulphur-coated urea showed maximum nitrification inhibition. A combination of one third sulphur-coated urea at planting + two thirds ordinary urea 30 days later yielded 12·3% more maize grain than ordinary urea in the same proportion at the same times of application.

Description: SUMMARYIn order to examine whether high yield of maize could still be maintained at high plant densities by creating an ‘erectophile canopy’ through artificial defoliation of laminae, an experiment at Pantnagar, India, was made on the effect of density, stage and degree of defoliation in two divergent seasons, Kharif (rainy) and spring, of the year 1972. The defoliation treatments were either partial (clipping off the apical half of individual leaves) or complete (full leaf removal) and were imposed at three stages of plant growth, namely when 10 or 16 leaves were fully open or 12 days after silking. These treatments were applied at two plant densities, 60000 and 90000 plants/ha.Grain yield of maize increased significantly with the increase in population density in the spring season. The trend was diametrically opposite in the Kharif season. Defoliation at the 10th fully open leaf stage produced more grains than defoliating 12 days after silking, which in turn produced more than defoliating at the 16th fully open leaf stage, when plants were in full bloom. Increase in the degree of defoliation at the latter two stages of plant growth reduced grain yield, the effect being more at the 16th leaf stage. However, 50% defoliation at the 10th leaf stage increased grain yield in the Kharif season.The percentage protein content of grain declined with the increase in population density whereas increase in degree of defoliation increased the grain protein content. Higher protein content of grain was recorded in the spring than in the Kharif season. The leaf protein decreased as the plants neared maturity, especially at the higher degree of defoliation treatments.Sucrose and reducing sugars declined significantly with the increase in degree of defoliation. The reduction in sucrose was large enough to account for the reduction in total sugar percentage. Similar trends were observed in the sugar-to-protein ratio.

Description: SUMMARYData are presented from an experiment made in two crop seasons, to examine the effects of plant density and degree of defoliation at different stages of growth in maize at Pantnagar, India, on the dry-matter accumulation in different plant parts, leaf area index (LAI), time of silking and grain yield components.Different patterns of dry-matter accumulation in various plant parts was observed. Silking was delayed by increasing plant density. Defoliation (even partial) at the 16th fully expanded leaf stage resulted in substantial reduction in LAI and such yield components as number of ears, ear length, ear diameter and 1000-grain weight. On the other hand, partial defoliation done at the 10th fully expanded leaf stage to simulate an ‘erectophile canopy’ led to yield increases even under high plant density (90000 plants/ha) in the Kharif (rainy season), mainly through an increase in number of ears, 1000-grain weight and grain to stover ratio coupled with a reduction in barrenness and percentage of lodging. It is suggested that an increase in the photosynthetic efficiency per unit area of leaf resulting from the ‘erectophile canopy’ is the reason for these effects.

Description: SummaryThe effects of differing degrees of leaf removal was studied in maize at different stages of growth and in varying plant densities. In control (untreated) plants significantly lower grain yield/unit area at the higher density (90000 plants/ha) was associated with greater barrenness, percentage of lodging and time taken for silking. Increase in plant density from 60000 to 90000 plants/ha led to a reduction in length and diameter of the ear and in weight of 1000 grains. Delay in the time of leaf removal from the tasselling stage until 10 days later increased yield, number of ears, ear length, diameter and test weight and decreased percentage of barrenness and lodging.Leaf removal adversely affected yield and yield components (number of ears, percentage of lodging, ear size and test weight of 1000 grains). Complete leaf removal at tasselling time delayed silking and reduced lodging.

Description: SUMMARYExperiments made over a period of 2 years (1975–6) covering three crop seasons at Pantnagar, India, on the comparative utility of intercropping the principal maize crop with legumes in economizing fertilizer N requirements of the former, indicated that among soya bean, cowpea, pigeonpea and groundnut, soya bean was the most suitable. At 40 kg N/ha intercropping maize with soya bean gave 19·5% more yield than taking it as a pure crop. When the option to use adequate fertilizer N does not exist, as is invariably the case with the average Indian farmer, intercropping maize with legumes, such as soya bean, is the logical way out. All the intercropping treatments left sufficient residual fertility to significantly increase yield of a wheat crop given no fertilizer which followed maize.