| The method to improve water conditions of the orchards has been the key to get prolific and dependable crop in the northwest loess plateau dryland region. Demonstration and utilizing drought-resistant technology, like ground mulching largely alleviated the restrictions of limited precipitation and seasonal drought on fruit production in mid-east loess plateau dryland region of Gansu Province.Select mature orchard where average annual rainfall is about 500 mm in semi-arid hilly and gully region on the northwest loess plateau, a location field experiment was conducted to study the effects on water/heat control, water balance utilizing, water use efficiency and yield under the condition of PFM(plastic film mulch), SM(straw mulch) and CT(clean tillage), tested and analyzed the changes of the chlorophyll fluorescence characteristics, photosynthesis of peach leaf and fruit quality.Tested and analyzed spatial and temporal variation of soil water/heat, soil nutrient, soil mineralization character, the microbial biomass and enzyme activity of different soil layer(0 ~ 30 cm and 30 ~ 60 cm) under the condition of PFM, JM and CT either. Results and conclusion are as follows:1. Compared with CT, PFM increased soil temperature, and SM(P<0.05) decreased. Two kinds of cover increased the gravimetric water content absolute value of 1.9~2.9%; Evapotranspiration decreased by 82.5mm(SM) and 49.3mm(PFM). Under the cover condition, WUE increased from 5.7 kg?m-3(CT) to 8.1 kg?m-3(PFM) and 9.0 kg?m-3(SM), and the yield increased from 25.2t?ha.-1(CT) to 32.2t?ha.-1(PFM) and 32.5t?ha.-1(SM).2. In the fruit rapid expansion period, PN(net photosynthetic rate) of PFM and SM were 13.1 μmol?m–2?s–1and 12.2 μmol?m–2?s–1, increased by 14.9% and 7% than CT(11.4 μmol?m–2?s–1). Chlorophyll fluorescence kinetics analysis at 13:00 showed that J point on OJIP curve of CT rised significantly compared with PFM and SM, and relative variable fluorescence intensity VI differences between each treatment were not significant. Compared with CT, maximal photochemistry efficiency(TR0 / ABS) of PFM and SM increased by 3.8% ~ 5.1%, Photochemical performance index increased by 36.4%~41.2%.3. There were differences in the change of soil organic matter content and soil nutrient content of different depth between each treatment. In 0~30 cm layer, soil organic matter content in PFM was signidicantly lower than in CT and had no great change in JM. The change rules of total nitrogen content and organic content were accordant. Soil total phosphorus content increased in PFM and JM than in CT. In 30~60 cm layer, soil total phosphorus content in PFM and JM were significantly lower than in CT.4. Both PFM and JM treatment significantly improved the orchard soil available nutrients, but there was difference. In 0~30 cm soil layer, alkali-hydrolyzable nitrogen in PFM and JM increased by 27.7% and 14.6% than in CT. Compared with JM, available phosphorus in PFM decreased by 31.0%, and available potassium increased by 5.0%. In 30~60 cm soil layer, compared with JM, alkali-hydrolyzable nitrogen in PFM increased by 9.7%, available phosphorus and available potassium in PFM decreased by 11.5% and 12%.5. Soil organic carbon, nitrogen, phosphate mineralization rate ranges with the soil depth, and there were differences between each treatment. Mineralization rate were faster in 0~30 cm soil layer than in 30~60 cm layer, and the rate of organic carbon in JM was the fastest, PFM was the slowest. Compared with CT, the rate of nitrogen in PFM and JM increased by 41.4% and 23.7%, The rate of phosphorus in PFM and JM increased by 23.8% and 10.2%. Mineralization rates of nitrogen and phosphorus in PFM increased by 12.5% and 11.1% than in JM. In 30~60cm soil layer, mineralization rate of nitrogen in PFM increased by 10.1%. Generally, mineralization rate of each nutrient were faster than in CT.6. PFM and JM significangtly incresed the activity of soil urease and phosphatase, decreased the rhizosphere catalase activity, increased the microbial carbon and nitrogen contents. In 0~30 cm soil layer, urine enzyme activity in PFM and JM increased by 21.5% and 51.42% respectively, phosphatase activity increased 11.2% and 21.4% respectively than CT, JM was more beneficial to the improvement of the microorganism and enzyme activity.In conclusion, in the peach orchard, PFM and SM significantly improved the rhizosphere soil water content, PFM improved the soil temperature, SM decreased soil temperature. PFM and SM significantly increased WUE and the yield. In the fruit rapid expansion period, PFM and SM improved the leaf net photosynthetic daily average rate. PFM and JM improved soil enzyme activity and promoted the decomposition of soil organic matter, accelerated the N,P,K mineralization rate, increased the contents of soil available nitrogen, phosphorus and potassium, increased the fruit yield and quality. JM(uncovered at the end of June) is more advantageous to the improvement of the soil environment. |
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