A Study On Growth And Nitrogen Nutrition Of Barley-rice Cultivated In Different Water Management Systems In Long Term Field Experiment

Rice cultivation in waterlogged condition is a traditional way, which wastes a lot of freshwater resource. It is of great importance to practice water-saving cultivation and improve soil quality in development of sustainable agriculture. In past years, a novel cultivation system of rice crop in aerobic soil showed a greart potentail of water saving agriculture. But the systematized research was rarely reported about the barley-rice crops cultivated in different ground covering. Field experiments were carried out in Yancheng Academy of Agriculture Science, Jiangsu province from 2002 to 2004 to study the water and nitrogen management in barley-rice rotation system with the rice cultivated both in aerobic and waterlogged conditions. In rice cultivation, there were a waterlogged soil treatment and three aerobic soil treatments with different surface covers, such as plastic film (PF), rice straw mulching (SM) and without any mulching (B). After rice season, barley was planted in same year with nothing mulching in all treatments. Results obtained are listed as follows:The contents of NH₄⁺-N and NO₃^--N in soil changed with the environmental condition such as crop uptake, fertilizer application, and soil water content. They could reach mg kg^-1 and 40mg kg^-1 respectively in surface layer after fertilizer application in rice season, while 10mg kg^-1 and 120mg kg^-1 in barley season. But they all were below 10mg kg^-1 in layer of 20-80 cm in the two seasons. The ratio NH₄⁺-N to NO₃^--N was changed with the different contents of water in soil resulted from different ground covering. The ratio was increased with the increase of water contents. The soil covered with rice straw could decrease nitrogen loss significantly. The soil without any mulchings had high content of NO₃^--N because of the intensive nitrification, and the waterlogged soil had almost no nitrate.The grain yields of rice cultivated in aerobic soil mulched with straw were lower than waterlogged rice in 2004, while they were higher in 2003. However, the grain yields of ricecultivated in aerobic soil mulched with straw were always higher than the other two aerobic treatments in the two seasons. The rice grain yields in the treatment of bare soil were the lowest among all treatments. Barley crop rotated in the treatment of waterlogged rice cultivation grwoed worst, but the best in the treatment of soil covered with rice straw in rice season. Compared to the treatment of bare aerobic soil, grain yields of barley cultivated in soil covered with straw was increased by 14%, while treatments of waterlogged soil and plastic film covering soil decreased by 9% and 4.5% respectively in 2002. Compared to previous waterlogged soil in 2003 rice, the grain yields of barley grown soil previously covered with plastic film, straw and nothing mulching were increased by 14%, 20% and 3% respectively, while in 2004 they were decreased by 20%, 13% and 24% respectively.Great difference in nitrogen uptake intensity between barley and rice existed. For barley, the major nitrogen uptake period was in full fruit period and before these periods the nitrogen uptake was about lkg hm^-1 d¹. But for rice, the major period of nitrogen uptake was in booting period, and in these periods the nitrogen uptake rate was during 0- 4kg hm² d^-1.Nitrogen use efficiency (NUE) was diffenent in defferent treatments. In 2002, the NUEs by barley growing in the soils previously covered with plastic film, bare ground and waterlogged were decreased by 9%, 7.8% and 7% compared to the treatment of soil previously covered with rice straw, respectively, In 2003, the NUEs by rice growing in soils covered with plastic film, straw and nothing mulching were decreased by 4.2%, 5.6% and 2.7% respectively, compared to waterlogged treatment, while in 2004 they were increased by 6.0%, 3.4% and 12.2%.Different soil surface mulching changed the distribution of nutrient in plant leaf segment by changing content of water and nutrient in soil. The treatment of ground covered with straw improved the content of nutrients o...