| Farmland straw mulching planting is a sort of agricultural technique for field water conservation and fertility betterment of achieving the onsite collection, utilization and storage of rainwater through changing the micro-meteorological condition on the farmland surface, which is suitable for the dry flatland and gentle slope dry land in non irrigation area or irrigation lack area. Experiment was carried out at Rainfed Agriculture Base at Pengyang county in Ningxia Province of Northwest Agriculture & Forestry University(106°32′～116°58′E,35°41′～36°17′N)in 2007～2010. The main study results are as follows:1. The fixed position experiment of continuously for 4 years(2007～2010) indicated that there existed seasonal and hierarchical difference in effect of different straw mulching amounts on soil moisture, and in growth period of crop, Soil Moisture was generally positively correlated with straw mulching quantity. In cultivation experiment of wheat, under the treatments of straw mulching amounts of 9 000,6 000 and 3 000kg·hm-2, in the wheat growth period of 4 years experiment, compared with CK, the soil average moisture content in 0～80 cm soil layer increased by 7.26%(P<0.05),5.76%(P<0.05) and 2.85% respectively, increase of 0.81%～2.66% for 80～120 cm soil layer, while as for 120～200 cm soil layer did have an obvious difference among every treatment. In cultivation experiment of maize, with straw mulching amounts of 1 3500, 9000 and 4 500kg·hm-2 , in the maize growth period, soil water storage of the annual average from 2007 to 2010 in 0～200cm soil layer increased by 15.47,10.79 and 6.26 mm respectively compared with CK, with an obvious difference among every treatment(P<0.05). In this study, treatments with the most significant moisture conservation effect were with wheat field straw mulching amounts of 6 000 kg·hm-2and 9 000 kg·hm-2 and maize field of was up to 9 000 kg·hm-2.2. Under the continuous and fixed position experiment, after crop collection in 2010, soil nutrient content in 0～40 cm soil layer under different straw mulching amounts increased in different extent. In cultivation experiment of wheat, straw mulching amount up to 6 000kg·hm-2 had have an obvious effect. Under treatment of straw mulching amount of 9 000kg·hm-2, the soil organic carbon, total nitrogen, total phosphorus, total potassium, active organic carbon, available nitrogen and available potassium content in 0～20cm soil layer increased by 14.04%,4.05%,6.32%,10.82%,25.32%,11.71% and 18.96% ( P<0.05 )respectively compared with CK; under the straw mulching amount of 6 000kg·hm-2, the soil organic carbon, total nitrogen, total phosphorus, total potassium, active organic carbon, available nitrogen and available potassium content in 0～20cm soil layer had increase of 9.71%, 4.05%, 7.34%, 13.04%, 38.96%, 9.18% and 21.62%(P<0.05)respectively compared with CK, while for 3 000kg·hm-2 did not have an obvious increase over generally CK. In cultivation experiment of maize, under straw mulching quantity up to 9000kg·hm-2 the soil organic carbon, total nitrogen, total phosphorus, total potassium, active organic carbon, available nitrogen, available phosphorus and available potassium content in 0～20cm soil layer increased by 31.84%, 34.09%, 14.08%, 9.18%, 0.93 g·kg-1,18.84%, 15.32% and 39.87%(P<0.05)respectively compared with CK, increase of 26.18%, 34.09%, 11.27%, 12.79%, 0.64g·kg-1, 48.44%, 11.70% and 34.47%(P<0.05)for 1 3500kg·hm-2, while 4 500kg·hm-2 had no obvious increase over generally CK.3. The different straw mulching amounts enhanced the activity of soil invertase, phosphatase, urease and catalase in various degrees. After the winter wheat harvest in 2010, under the treatments of 9 000, 6 000 and 3 000kg·hm-2 , soil urease activity of 0～20 cm soil layer increased by 9.83%,10.40% and 9.83%(P<0.05)respectively compared with CK; soil invertase activity under different treatments had increases of 18.19%, 22.89% and 7.74%(P<0.05)respectively over CK; increases of 9.38%(P<0.05), 11.94%(P<0.05)and 3.45% respectively over CK for phosphatase activity under different treatments. In the maize cultivation experiment, under the mulching amounts of 13 500, 9 000and 4 500kg·hm-2, soil invertase activity of 0～40cm layer increased by 61.52%, 43.18%, 23.49%(P<0.05)significantly respectively compared with CK; significant increases of 11.37%, 9.10%, 5.41%(P<0.05)respectively over CK for soil urease activity under different treatments.4. Years of straw mulching had an obvious improving effect for the topsoil physical characters. Soil treated with straw mulching had good structure, which not only decreased soil bulk density, increased soil porosity, and also promoted the formation of soil aggregation. After the wheat harvest in 2010, under the treatments of 9 000,6 000 and3 000kg·hm-2, the soil bulk density of 0～20 cm layer decreased by 6.58%(P<0.05),7.69%(P<0.05),4.32% respectively compared with CK; this study shows that the mechanical stable soil aggregate contents of >5mm under the treatments of different straw mulching amounts were all higher than CK, while the mechanical stable soil aggregate contents of 2～0.5mm in 0～10cm and 10～20cm soil layers decreased to different degrees. After the maize harvest in 2010, under 13 500,9 000 and 4 500kg·hm-2 , the mean soil bulk density of 0～60cm layer decreased by 4.32%(P<0.05),3.60%(P<0.05),1.44% respectively compared with CK; with straw mulching amounts of from high to low, the soil water stable aggregate content of > 0. 25 mm in 0～10 cm layer increased by 97.08%,78.36%,49.71%(P<0.05)respectivly compared with control, increases of 86.24%,84.66% and 32.28%(P<0.05)for 10～20 cm soil layers over control, while no significant differences compared with 13 500 kg·hm-2 and 9 000kg·hm-2, while all had significant differences compared with 4 500kg·hm-2.5. The treatments of different straw mulching amounts had an obvious effect on the crop growth. After the mulching treatment, in the crop maturation stage, the winter wheat mean biomass of 3 years increased by 23.34%～27.87% compared with control. The determination under 13 500, 9 000kg·hm-2 in 2008 presented the increase in spring maize plant height by as high as 25.14% and 22.04% over control, increases of 17.04% and 14.14% over 4 500kg·hm-2, all with significant differences(P<0.05),while no significant difference between 4 500kg·hm-2 and CK(P>0.05). The maize photosynthetic rate, transpiration rate and single leaf water use efficiency under different mulching treatments all their increases. Under1 3500, 9 000 and 4 500kg·hm-2, at silking stage of the maize, the 12:00～15:00 photosynthetic rate increased by 7.26, 8.48, 2.63μmol·m-2·s -1 compared with CK, increases of 0.88, 0.91, 0.17μmol·m-2·s -1 respectively over CK for transpiration rate, and with significant differences between 1 3500, 9 000kg·hm-2 and control ( P<0.05); the 8:00～12:00 single leaf water use efficiency increased by 21.92%, 19.21% and 9.19% (P<0.05) respectively compared with CK.6. The preliminary study results of 4 years show that for winter wheat or spring maize cultivation, straw mulching can both increase crop yield and water use efficiency. Under 3 000,6 000 and 9 000 kg·hm-2, winter wheat yield of 3 years averagely increased by 15.92%(P<0.05), 8.47%(P<0.05)and 2.35%, water use efficiency increased by 33.05%, 35.72% and 41.68%(P<0.05), and water use efficiency under 9 000 kg·hm-2 increased by 6.48%(P<0.05)compared with 3 000kg·hm-2. Under 1 3500, 9 000 and 4 500 kg·hm-2, spring maize mean yield of 4 years increased by 12.03%, 14.23% and 2.42% respectively compared with control, and water use efficiency had increases of 8.87%, 10.64% and 1.59% over CK. |
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