Study Of Farmland Ecological Effect On Dry Area With Straw Mulching Conditions In South Of Ningxia

This research conducted winter wheat and spring maize cultivation experiments by setting different stalk cover rates on dry farmlands in semiarid areas in Southern Ningxia for two successive years. Through deep analysis of soil moisture, soil nutrient, enzyme activity and crop growth response under different rates, this paper aims to perfect stalk cover cultivation model and comprehensive technology of water reducing and saving in semiarid areas.1. By mulching treatment, crop growth is significantly superior to the control group. Plant height of wheat improves by 7%～14.9% and biomass accumulation increases 26.9%～40% compared with the control group. Increasing with the stalk cover amount, agronomic characters observed values of spring maize, as plant height, stem diameter, leaf area, and etc, improve obviously. In mature period, plant height of spring maize receiving high, middle, low mulching cover amount treatment improve by 25.9%,16.4%,13.2% respectively; stem diameter increases by 17.7%,16.3%,6.6% respectively; leaf areas increase by 48.9%,33.6%,21.4% respectively.2. Increasing with mulching cover amount, soil water content is superior to the control group. After harvesting of wheat under treatment of mulching cover amounts of 3000 kg/hm2,6000kg/hm2,9000kg/hm2 ,soil water contents increase by 13.1%﹑19.8%﹑26.1% averagely compared with the control group. When mulching cover amount is 3000 kg/hm2 , wheat yield and water use efficiency improve by 16.7% and 33.8% respectively. When yield is 3331.42 kg/hm2, spike length and grain number per spike increase by 28.7% and 27.6% respectively. In maize cultivation experiment, increasing with mulching cover amount, soil water preserving and storage effect increases also. By mulching cover treatment, during whole growth period of maize, water consumption amount decreases by 2.72%～6.66%. In this two-year experiment, every year the crop yield reaches the highest when the mulching cover amount is 9000 kg/hm2, and the yield is 5439.3 kg/hm2 and 5516.5 kg/hm2 respectively, increasing by 18.7% and 14.9% compared with the control group. When mulching cover amount is 4500 kg/hm2, moisture conservation effect is not obvious, with water use efficiency increases by 3.25% averagely. When mulch cover amount is 9000 kg/hm2 and 13500 kg/hm2, moisture conservation effect is significant, with water use efficiency of maize increase by 28.34% and 27.26% averagely compared with the control group.3. By mulching treatment, Crop photosynthetic rate and single leaf water use efficiency improve obviously. Under different mulching cover amounts, maize photosynthetic rate, transpiration rate and single leaf water use efficiency all increase, positively correlated with the mulching cover amount. In big trumpet period, maize photosynthetic rate increases by 22.5%～44.9%, transpiration rate increases by 8.57%-33.6%, and single leaf water use efficiency increases by 8.59%～21.4%, compared with the control group.4. Under mulching cover treatment for two years, soil nutrient content amount increases greatly. Content of available nitrogen, available potassium and organic matters in soil layer of 0～40cm deep of cornfields increase by 11.8%～15.7%, 6.4%～11.8% and 44.4%～55.5% respectively. Influence of Mulching cover amount on comprehensive soil nutrients content amount in cornfields is mainly in the farmland deep of 0～20cm, with organic matters content increases by 24.9%～25.9%,total phosphorus content increase by 6.9%～16.7%,total potassium content increases by 3.7%～7.2%. Influence rules of straw mulching amount on surface soil available nutrients contents is generally similar. By mulching cover treatment, available nutrients content in soil deep of 0～20cm increase all, correlated with the mulching cover amount.5. By mulching treatment, invertase enzyme activity and phosphatase enzyme activity increase significantly, but urease membrane activity and catalase activity receive no obvious effect. After harvest in cornfields in year of 2009, invertase enzyme and phosphatase enzyme increase by 7.7%～11.4% and 30.9～42.9% respectively. Influence of cornfields on soil enzymes activity is mainly in the soil layer of 0～20cm, with invertase enzyme and phosphatase enzyme increase by 3.1%～19.4% and 13.7～35.3% respectively compared with the control group. Influence in the soil layer of 20～40cm is not obvious.6. By mulching treatment, soil bulk density decreases significantly. After crop harvest, mulching cover amounts of 9000 kg/hm2,6000kg/hm2,3000kg/hm2 on soil bulk densities in soil layer deep of 0～20cm decrease by 5.5%, 2.3% and 0.8% respectively compared with CK. After maize harvest, under different mulching cover amounts, soil bulk density in soil layer deep of 0～60cm decreases by 0.7%～3.6% obviously compared with the control group. Mulching cover amount also has obvious effect on soil aggregate composition. After maize harvest, mulching treatment makes soil aggregate bigger than 5mm in soil layer below 20cm obviously higher than that in surface layer. Contents of particles large between 0.25 to 1mm receiving different mulching cover amounts treatment is obvious higher than the control group. After maize harvest, agglomerates of particle size >0.25mm has trend of increasing with mulching cover amount in the soil layer deep under 20cm, and he highest content of agglomerates of particle size >0.25mm is receiving mulching cover amount treatment of 9000 kg/hm2.