Dry soil bulk density increased from 1.42 g/cm 3 with ordinary ploughing to 1.69 g/cm 3 with puddling twice and to 1.80 g/cm 3 with soil compaction. Consequently, saturated hydraulic conductivity decreased from 113 mm/day with ordinary ploughing to 48 mm/day with puddling twice and to 29 mm/day with soil compaction. The irrigation requirement was 2295 mm with ordinary ploughing compared with 1350 mm with soil compaction. Dry weight of weeds was only 0.6 and 0.7 t/ha with puddling twice and soil compaction, respectively, and 3.9 t/ha with ordinary ploughing. The highest grain yield of rice (4.5 t/ha) was obtained with puddling twice, due to effective weed control. Weeds shared 57 and 35% of the nutrient (N+P+K) with ordinary ploughing and puddling once, respectively, as compared with only 8 and 15% with puddling twice and soil compaction, respectively. The ratio of total biological yield (grain + straw + weeds) to total nutrient (N+P+K) uptake was 59.0 with puddling twice and soil compaction as compared with 53.5 with puddling once and 50.0 with ordinary ploughing. This suggests that tillage practices may affect the efficiency of the use of soil and applied nutrients by the rice crop.

Effect of tillage practices on irrigation requirement, weed control and yield of lowland rice

Chlorophytum borivilianum Sant. and Fernand (Safed musli) plants were raised in fertile soil in earthen pots and subjected to various durations of water deficit and waterlogging (5 and 10 days). The analysis of macroelement in the leaf tissue revealed that water deficit caused a decline in levels of phosphorus and potassium while there was accumulation of calcium, magnesium and sulphur. In the leaf tissue of waterlogged plants reduction in phosphorus and potassium content was noticeable while the levels of calcium, magnesium and sulphur were increased. Potassium and sulphur contents were found to be reduced in the tuber tissue by both water deficit as well as waterlogging treatments. An increase in phosphorus and magnesium content was noticed in water deficit stressed tuber tissue while similar trend was noticed in case of magnesium under waterlogging stress. The micronutrient composition was also altered due to both kinds of stresses. The contents of iron, zinc and manganese in the leaf tissue were incre...

Influence of water deficit and waterlogging on the mineral status of a medicinal plant Chlorophytum borivilianum.

Four soil moisture and two nitrogen levels were combined in eight treatments to study moisture and nitrogen effects on Dular (June–September crop) and Patnai-23 (June–November crop) varieties of rice. Both the varieties when grown under natural precipitation yielded significantly less than at other moisture levels. Whereas there were no significant differences amongst the three treatments of submergence (15–10 cm), cyclic submergence (15–0 cm) and cyclic wetting-drying (saturation to field capacity) for Dular rice, the former two treatments proved better than the latter for Patnai-23 rice. Dular responded to the treatments of cyclic wetting-drying in a way similar to that of submergence because the crop completed its life cycle during the period of low evaporative demand. Among the levels of nitrogen, 40 kg N/ha proved optimum for Dular rice and 6O kg N/ha for Patnai-23 rice. The increase in yield of grain was associated with increase in the number of panicles, number of spikelets/panicle and percentage of ripened spikelets. The concentration of N, P, Fe and Mn in the plant was maximum under submergence followed by cyclic submergence, cyclic wetting-drying and natural precipitation. Higher levels of nitrogen increased only N and P contents in the plant.

Water and fertility management of rice varieties under low atmospheric evaporative demand.

Limited moisture supply caused reduction in leaf area, number of effective tillers, ratio of sound to unsound grains and the nitrogen, phosphorus, iron and manganese content of rice. Crop yield was adversely affected in the absence of standing water. Two levels of nitrogen (40 and 60 kg.N/ha.) caused no significant difference in yield in 1965, but in 1966, when 30 and 60 kg. N/ha. were used, the latter gave better yields.

Panjab Singh

Papers

Effects of Moisture and Nitrogen on Growth, Yield and Mineral Content of Rice