Study On Partial Nutritional And Physiological Characteristics Of Rice Under Water Stress Condition

The developments of economy, society, science and technology of most countries in the world have been threatened seriously by the shortage of water these days. Our country has been troubled with the same problems. Limited water resource has become one of the main restrictive factors to sustainable agriculture. Traditional waterlogged cultivation of rice consumed a huge amount of water and led to some serious environmental problems especially when large dosage of fertilizer and pesticide had been applied. Water saving agriculture has evidently become the correct direction of the sustainable agriculture.As rice has the adaptation to both water-lodged and aerobic condition, the new kind of water saving mechanism, aerobic cultivation of rice is gaining more and more attention from scientists, government, and farmers. The importance of development of water saving cultivation of rice has been discussed through analysis of present water resources and tendency of water demand in the future. A series of pot and field experiments and imitating experiments in lab were carried out to study the scientific problems as follows, (1) effects of different water and nitrogen management conditions on the manganese nutrition of rice, (2) the effects of different water and nitrogen management conditions on partial physiological and morphological response of rice and (3) the effect of rare earth elements application on the growth and yield of rice cultivated in non-full irrigation condition.The main results are as follows.1. Although available manganese is usually abundant for the growth of rice cultivated in waterlogged condition, the rice crop may suffer from its deficiency when cultivated in aerobic soil since the soil properties are totally different from waterlogged. Solubility of manganese is very low in soils with high Eh and/or high pH. A field experiment with five different depth (10, 20, 30, 40 and 50 cm) of groundwater, and a pot-experiment with five treatments of ammonium-nitrate ratio (100/0, 75/25, 50/50, 25/75 and 0/100) were conducted to study the characteristics of manganese nutrition of rice in non-full irrigation condition. Moreover, the contents of manganese extracted by 1 mol·L-1 HCl of rice plant samples of 8 cultivars from both aerobic and waterlogged cultivation were analyzed to study the effect of water regimes on manganese content of rice plants. The results were as follows. (1) The average content of available Mn (3.96 mg·kg^-1) of 5 layers of the soil treated with 10-cm depth of groundwater was significantly higher than that (1.52 mg·kg^-1) with 50-cm depth of groundwater, and the...