Research And Extension Of Cultivation Techniques Of Mulching Whole Year In Wheat Field In Weibei Plaeau

With the growth of population and improvement of people's living standard, our needs for food and fiber increase remarkably, but what we have to confront is the rigorous situation that the land and fresh water resources have been shrinking day by day. Additionally, large assumption but difficult complement of under ground and surface water lead to the havoc of drought wrecks. So to develop irrigation agriculture is subjected to a lot of restrictions, forcing us to throw attention to dry land farming. The arid and semi-arid area and farmland area for 51,000,000 hectare in our country cover 56% and 51% of national territory separately. The study on dry land farming started late but developed rapidly. And the research and demonstration on dry land agriculture technique have been put into an important and strategic position.There are 3,600,000 hectare farmlands in Shaanxi province,2,400,000 hectare of those depends on natural rainfall accounting for 66% of the total farm land. Though the coverage of farmland per person is large, the soil layer is deep, the light and air temperature are feat, the potential of agriculture production is large, some problems such as drought seriously limit the continuous and quick developing of agriculture. According to the statistical data, there occurred 972 times drought wrecks from 1 to 1990 A.D totally, one time every two years. So to resolve the problem on water shortage in dry land become a strategic choice to develop agriculture production.The arid area covers 75% of total farmland in Weibei Rainfed Highland with 3.1 mu per person and average rainfall for 500～700 mm.. The large storage of moisture, ample resource of light and heat and large occupation of farmland per person produce a vigorous potential in production of provision, vegetable oil, and fruits. On the contrary, threat from drought, insufficient rainfall without coinciding with crops'growing period and invalid evaporation reaching to 80% of total rainfall due to the greenhouse effect make up another important aspect. Such how to exert the cultivated measures and preservation moisture fully is a key problem in dry land farming.At present, most people emphasize on the hydraulic engineering but only a few ones advocate innovation and breakthrough in new cultivation techniques. Based on the problems of preservation of soil moisture in Weibei Rainfed Highland, the study on straw mulching in the entire growth stages were carried out through reforming the cultivation techniques to reduce the moisture evaporation. The main results are as follow: (1) amount of natural rainfall were recorded in Ganjing town Heryang County , which average rainfall for 582 mm and 333.6 mm in fallow period in summer which covers 57% of the total . And the nutrient content in rain water and snow were measured. (2) Dynamic determination of soil moisture was carried out. Based on the measurement of depth of Loess soil, nutrients contents in underground water and forms and quality of soil moisture, the law of bi-directional implementation of soil moisture was put forward. By determination the loess soil of seepage flow law under the natural state and the action of straw mulching techniques, the largest storage of moisture was 542.4 mm in 2 m depth of soil profile , which occupied 86% of field moisture capacity by straw covering under different crops planting. Thought the available water capacity reached 336.5 mm, the supplement to ground water caused by straw covering was not obvious; (3) By selection wheat cultivars and identity their disease resistance, the vital role of the variety in the covering cultivation was definited under straw mulching in entire stage. The effective method for the appraisal of wheat blue dwarf was found. The new rating standard of evaluation blue dwarf and the viewpoint that the blue dwarf had the outbreak center were proposed. There obtained the viewpoint that straw covering technique was very strict to the variety selection and the most varieties were not suitable for this technique. By screening test the suitable varieties with drought resistance , high and stable production and anti-blue dwarf were as follow: Yan D27 , Dong Feng No.1, Jin-mai 47 and Shi-86-5144; (4) By analysis of the experiment results of wheat straw-covering-cultivation and the runoff observation , the mechanism that the straw covering reduces soil moisture evaporation was opened out, the effect that the straw covering preserved moisture and increased the crop yield was determined, the effect of the ground temperature on the soil moisture evaporation was definited, the influence to heat preservation and temperature decreasing from straw covering and the function to prevent soil erosion and to improve biological cultivation (increasing earthworms and roots) caused by straw covering were also determined. (5) Arranged the experiment to prevent the main weeds under the cover condition, screened the chemicals"world masurium", which was secure to wheat but effective to the Japanese brome; and proposed weeds preventing and controlling method in the non-planting period; (6) By the planting time experiment under straw covering situation, pointed out the suitable sow time was 7 to 10 day and the serious occurrence of blue dwarf and the weeds in the early planting time was discovered. The machines and tools matching to straw mulching situation were designed, developed and screened independently, including pesticide spraying machines, fertilization and seed sowing machines. Their patents were obtained and the mechanized work flows proposed. (7) The present problem and current situation such as the reason of extension straw covering cultivation techniques but not pushing broadly was analyzed during the research. The extension direction was also pointed out and standing stalk mulching were proposed finally in the entire growth stage.