Dynamic Change Of Soil Water And Fertilizer Under Conservation Tillage Practices Upon Minor Grain Crop

Sandy Area along the Great Wall in Northern Shaanxi is an important rain-fed agriculture area in the north of China. This area is featured by short period of free frost and little amount of rainfall which is unevenly distributed and mainly come from June to October, resulting in the severe spring drought and sowing difficulty, combined with the soil erosion and harsh ecological environment, the output of crop in this area is low and unstable. Even worse, the grain farming practices upon minor grain crop, a staple one in this area, added to the unfavorable condition. Therefore, the research on protective practices on minor grain crop is of vital importance to the agriculture development in this area.In order to reveal the dynamic change of soil water and fertility in the farming field, explore on and analyze the effect of protective farming practices on the growth and output of minor grain crop and the ecological effect it brings with in preventing wind and water erosion, such farming practices as no-tillage, soil loosening method, stubble mulch and film mulching techniques were conducted in Gushui village of Hengshan county in northern Shaanxi, and studied was the water effect and output benefit of adzukibean and broomcorn millet rotation system, water and fertilizer effect and output benefit of adzukibean and broomcorn millet soybean rotation system and water use efficiency and yield benefit of mung bean. The results were showed:1,Deep loosening farming techniques and no-tillage can help improve water use efficiency(WUE) of grains. The water consumption of broomcorn millet in the whole growth stage under deep loosening farming conditions was the same as the check, but the WUE was improved by 15.8%, in the case of no-tillage, the water consumption was 7.8mm more than the check, and WUE was enhanced by 15.7%, both indicating that deep loosening farming techniques and no-tillage play an important role in improving yield and WUE of minor grain crop. When the WUE was at the same level, the total water consumption under deep loosening farming condition was 7.34 mm less than that under no-tillage condition, showing that the deep loosening farming techniques is more preferable in WUE improvement in years suffering drought.In both cases of adzukibean and broomcorn millet, there was significant difference in output when different farming practices were performed. Contrasted with the check, protective farming practices was capable of decreasing farming times, saving labor force and financial input and obtaining high output. In 2004 with normal amount of rainfall, the yield of adzukibean under deep loosening farming condition was highest, and the net income was also highest, 1871.5 RMB more than that of the control per ha, and 1486.5 RMB more than that of the control when under no-tillage condition. In 2005 suffering drought, the yield of broomcorn millet under no-tillage condition was highest, and the net income was also highest, 270 RMB more than that of the control per ha, and 182.5 RMB more than that of the control when under deep loosening farming condition.2,WUE of adzukibean and soybean were highest with stubble height of 60 cm under no-tillage condition. Under no-tillage condition with stubble height of 10cm, 35cm, 60cm, the water consumption was the same for stubble height of 60cm and 35cm, but the WUE of grains with stubble height of 60cm was 0.707 kg/mm·hm~2 higher than that with stubble height of 35cm. Water consumption with stubble height of 60cm under no-tillage condition was 4.9% higher than that with the same stubble height but under conventional farming condition, and the same trend was applied to WUE of grain, which was 34.1% higher, indicating high stubble height under no-tillage condition is most favorable to improve WUE of grain.After three successive years of conservation tillage practices, the amount of organic matter, soil alkali hydrolyzable nitrogen unfolded an increasing trend, and available potassium and phosphorus decreased. Stubble mulch could improve the contents of organic matters in the tilth soil. Among the six treatments, largest improvement occurred in TS60 treatment. The amount of soil alkali hydrolyzable nitrogen under no-tillage condition with different stubble height was more than that under conventional farming conditions. When the same farming practices were conducted, the amount of soil alkali hydrolyzable nitrogen was highest with the stubble height of 35cm. the average amount of available phosphorous under no-tillage condition with different stubble height was lower than under conventional farming conditions. On the basis of same farming practices, the more stubble height, the less amount of available phosphorous. Significantly more was the amount of available potassium under conventional farming condition with different stubble coverage than that when no-tillage was performed.highest yields of adzukibean and soybean were reached when no-tillage was conducted with stubble height of 60cm, 348kg/hm~2和756.0 kg/hm~2, respectively.3,WUE of grain and dry matter was highest when film-covered double-furrow practice was carried out, 60.4% and 24.3% higher respectively than that in open cultivation(check), and there was significant difference in WUE of grain among different treatments.Highest yield was obtained under film-covered double-furrow practice, reaching 73 kg/hm~2, respectively 235.5kg/hm~2 and 73 kg/hm~2 more than under open cultivation and horizontal film covering condition Bio-mass was also highest under film-covered double-furrow condition.