Study On Synthetical Effects Of The Conservation Tillages And Its Ecological Economic Benefits

With the integrated methods the experiment was conducted to explore the regularity of soil water consumption and water use efficiency, contribution to the change of soil temperature, soil nutrients and moisture , efficiency for growth and development of crops and the yield output in different conservation tillage measure at Dingxi County, a typical semi-arid area of the Loess Plateau and Hexi corridor, and to evaluate the ecological function of conversation tillage by protecting water erosion and wind erosion in these area. The main results showed as follows:1. The dynamic change of soil water in the arid land can be divided into 3 periods: Water-conservation period, water-retaining period and water-consumption period. The water-conservation period begins from beginning of crop harvesting time, ends in mid-August, how lang of water conservation period and how much water can increase depends on rainfall character, covered or naked land and tillage situation. NT could increase the water storage during this period. From the end of water conservation period to sowing time next year is water-retaining and water loss period. In this period how much water loss depends on cover situation of farming land, NTS was suitable for water storage. Soil water situation depends on three factors e.g. natural rainfall, consumption of crops and water loss amount during the growth stage of crops, at seedling stage water storage varied with rainfall and water loss like undulation, at fast growth stage of crops the soil water storage was decreased, and at anthesis stage the water storage retained at the lowest level. The decrease of water storage depends on situation of crop growth. Crop rotation wheat-pea had more effective water storage ability than crop rotation pea-wheat.The variety of water storage in total section (0-200cm) was similar as in upper layer (0-30 cm), however, it was not obvious dominance in NTS at total horizon, it was very important to protect the water in upper layer(0-30cm). Different crop consumes different water amount, the consumption of water by spring wheat was much more than that by pea during the whole growth stage.2, The study on water situation and water-saving under irrigation condition in Hexi Corridor released that straw mulch on spring wheat field is a very important measure for water-saving. The optimum irrigation ration is 900m3 /hm2, conservational irrigation period is from mid- Sep. to the beginning of Nov. Effects of water -storage and water-conservation caused by straw incorporated were apparent. It was suggested that an amount of 600 m3 /hm2 +straw incorporated treatment is the best measure for water-saving and water-storage.3. The content of total N was increased by different conservation tillage measures during the experiment, especially in the top 0-30 cm soil layer, the average content of ammoniacal-N is 6.69 times as much as that before the experiment began. The increaseunder plough condition is more than that under no-tillage, the content of ammoniacal-N in soil layer of 0-30 cm in treatment T, TP and TS increased to 9.78, 7.19 and 8.14 times in comparison of the normal respectively. 5.00, 4.01 and 6.52 times in treatment NT, NTP and NTS. The change of ammoniacal-N was not obvious under rotation model, but increase of ammoniacal-N was very apparent in NTS treatment. The change of nitrate-N in rotation of wheat-pea was decreased (-0.97 times) and increased in rotation of pea-wheat (+1.42 times).Conservation tillage improved the content of available P. in the top of soil layer (0-30cm) the content of available P increase up by 193.59% in rotation pea-wheat, while 153.66% in rotation wheat-pea. In different conservation tillage the increase of available P was more in treatment NTP, NTS than that in other treatments. The change of available P in different section layers from 0 to 200 cm had no significantly different.Different tillage and crop rotation systems decreased the content of available K. the content of available K in upper layer (0-3 0cm), decrease more than deep horizon, and the averag...