| Water resource and its utilization in agriculture are mostly related to sustainable agriculture because of water shortage. Traditional water loddged rice cultivation will lead to huge water loss, and environmental problems due to large fertilizer and pesticide use. Rice has the adaptation to moise or dry condition, and it can be cultivated in aerobic condition with the same yield. As a new kind of water saving mechanism, aerobic cultivation of rice is gaining more and more attention form scientists, government, and farmers. A series of field experiments, pot experiments and imitating experiments in lab were carried out to study the effect of N forms on water use efficiency and on uptake of some nutrients, the effect of soil mulching on water use efficiency and grain yield and quality, and the effect of soil water moist on the growth and nutrient uptake of rice cultivated in aerobic condition.The main results are as follows.1. Water saving and grain yield were totally different in the different cultivation systems. With the same plant density and field management, net water consumption (transpiration plus evaporation) of aerobically cultivated rice was 47-67% of that of waterlogged cultivation with the water saving effects in aerobic cultivation being plastic film mulching > straw mulching > no mulching. Accumulated transpiration of plastic film muclched rice was higher than that of straw muched in early growth stage, and was lower in later growth stage. The grain yields of rice were 5846, 5401, 4528, and 4098 kg ha-1 in waterlogged cultivation, in aerobic cultivation with strawmulching, in aerobic cultivation with plastic film cover and in aerobic cultivation without mulching respectively.2. Supplying ammonium and nitrate at the ratio of 50/50 to rice crop in soil culture experiment could increase the chlorophyll content and photosynthesis rate, and thus increased grain yields and water use efficiency of rice crop. Soil available Fe, Mn, Cu and Zn content decreased by the utilization of high ratio of nitrate in nitrogen fertilizer, showing nitrate nutrition did make the soil more alkaline, which decreased the availabilities of micronutrients in soils.3. Rice fed with mixed nitrogen nutrition of nitrate and ammonium (with or without PEG) grew better than other treatments in hydroponic culture experiment. The highest water use efficiency was obtained at the ammonia-nitrate ratio of 75/25 without the addition of PEG6000 (a substance added to imitate dry stress) but the water use efficiency increased with the decrease of ammonia-nitrate ratio with the addition of PEG6000. Nitrate uptake of rice was increased in all treatments amended with both nitrate and PEG6000.4. Water content of rice plant was decreased from 93.2% to 76.2% twenty eight days after the treatment of water stress in the treatment of S AH while from 90.7% to 85.3% at the same time in the treatment of SWS, almost equal to those in the treatment of WC (from 93.5% to 88.3%). A significant decline of photosynthesis of the flag leaf of the rice was found in the treatment of SAH while there was no difference of photosynthesis of the flag leaves between the treatment of SWS and WC. Root activities seven days after earring in the treatment of SWS were significantly higher than those in WC but the reverse was true twenty one days afterwards. Dramatic decrease of root activities was found fourteen days after the treatment of water stress in SAH. There were no significant differences of productive ears, grains numbers per ear, percentage of filled grain and weight of one thousand grains between the treatments of SWS and WC but the percentage of filled grainsand weight of one thousand grains were significantly lower in the treatment of SAH than those in WC. In conclusion, non-full irrigation during the whole growth periods of rice crops can make almost the same growth situation as that in traditional waterlogged cultivation of rice, showing that the potential of water-saving in rice cultivation system is very challenging issue.
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