| Harmless treatment and comprehensive utilization of straw are urgent issues for agricultural clean process projects in China now.Straw mulching is an effective tillage method to deal with straw waste,it also plays an important role in improving the rhizosphere soil environment and promoting high yield and efficiency.This study aimed to explore the changes in cucumber growth characteristics,water consumption,rhizosphere soil physical and chemical properties under different combinations of irrigation quota and straw mulch,to identify the optimum combination of irrigation quota and straw mulch for autumn and winter cucumber by analyzing the effect of saving water and increasing production in solar greenhouse in the arid zone of central Ningxia,to fully analyze the response mechanism of rhizosphere soil moisture,air and heat for straw mulching measures,and to provide a theoretical basis for the large-scale promotion of straw returning to the field and realizing the utilization of resources.According to lab simulation experiments,four straw mulching levels T1(0.42 kg/m2),T2(0.83 kg/m2),T3(1.25 kg/m2),T4(1.67 kg/m2)and CK(no straw mulching)were set to study soil water infiltration characteristics.Field experiments were conducted with cucumber as the research object by using a twofactor randomized block design,including two levels of irrigation quota(W1,W2)and four levels of straw cover under the membrane(S1,S2,S3,S4)of Wuzhong National Agricultural Science and Technology Park in Ningxia.It was concluded that appropriate straw mulching had both positive and negative effects on rhizosphere soil,and had certain water-saving and yield-increasing effects on cucumber.The specific conclusions are as follows:(1)The results of lab simulation experiments study on soil water infiltration characteristics under straw mulch showed that the wetting front of vertical and horizontal moisture infiltration both showed a power function trend over time.The amount of straw mulch directly promoted the horizontal transport of water in the soil.The models of Philip and Kostiakov could well fit the relationship between the cumulative infiltration amount of soil water and time,and the migration distance of the vertical and horizontal wetting front under straw mulching.R2 was greater than 0.96,nRMSE was less than 10%,and IA was greater than 0.97.Straw mulch promoted the storage of soil water.In both vertical and horizontal directions,the moisture content of soil moist body was T4>T3>T2>T1>CK.(2)By studying the effects of irrigation quota and straw mulch amount under membrane on the soil environment of the cucumber root zone,it was found that straw mulching promoted the increase of soil pH by 0.2-0.41,and reduced the soil soluble salt content by 0.86-1.29 g/kg.Straw mulching could significantly increase the number of soil aggregates with particle size>0.25 mm and water-stable aggregates,improving the water stability and the soil aggregate structure.The R2.5 of soil aggregates and water-stable aggregates under straw mulching treatment were 84.52%～99.3%and 40.77%～55.1%,respectively.Compared with CK,it was significantly increased by 0.61%～16.57%and 2.29%～13.08%.Straw mulching was beneficial to the increase of soil organic matter,urease,catalase,cellulase and sucrase contents.Compared with CK,the organic matter content of the 2-year mulching treatments significantly increased by 10.75%-28.13%and 14.69%-27.63%,respectively.The contents of soil urease,catalase,cellulase and sucrase in straw mulching treatments were also significantly higher than those in CK.(3)By studying the effects and interaction mechanism of irrigation quota and straw mulch amount under membrane on the distribution characteristics of water,air and temperature in the cucumber root zone,indicating that straw mulching was beneficial to increase soil temperature in the 0-25 cm soil layer,increasing irrigation quota,and inhibiting soil temperature,showing W2>W1.Soil CO2 concentration decreased with the extension of the growth period,and increased with the increase of straw mulch,and showed W1>W2.The highest treatment of soil CO2 concentration was W1S4 in each growth period,which increased by 118%,76.96%,92.89%and 53.66%compared with the lowest treatment CK,respectively.For soil oxygen content,straw mulch amount irrigation quota,and the interaction between irrigation quota and straw mulch amount all had very significant inhibitory effects.The soil water storage capacity of 0-40 cm in the whole growth period was 65.77～77.51 mm.In the middle and late growth periods,straw mulching promoted the accumulation of water storage capacity,which increased by 0.62%～0.79%compared with CK.The oxygen content of soil decreased with the increase of straw mulch amount,which could be simulated by function yO=a1+b1e-cx at each growth stage.Soil water storage,soil temperature and carbon dioxide concentration increased with the increase of straw mulch amount at each growth stage,and soil water storage and carbon dioxide concentration could be simulated by function yw=a2+b2x and y=a+bx,and soil temperature could be simulated by function yT=<A1+(A2-A1)/[1+10(logx0x)p]at the first flowering stage,and soil temperature could be simulated by function yT=a3+b3x at the peak and end of the fruiting stage.The R2 of the above function was 0.8218～0.9990,and the simulation effects were good.According to the relationship between straw mulch amount and moisture,air and temperature,the relation formula of soil moisture-air-temperature in each growth stage was obtained.The relationship between water storage,temperature and oxygen content varied with the growth stage,showing that in a certain range,water storage increased with the increase of temperature and the decrease of oxygen content in the initial flowering stage in 2020 and 2021;at the height of fruiting,water storage increased with the decrease of temperature and the increase of oxygen content in 2020,and increased with both decrease of temperature and oxy gen content in 2021;at the end of growth,water storage increased with the both decrease of temperature and oxygen content in 2020 and 2021.The relationship between water storage,temperature and carbon dioxide concentration was consistent in every growth stage,showing that in a certain range,the water storage increased with the decrease in temperature and the increase of carbon dioxide concentration in 2020 and 2021.(4)Effects of irrigation quota and straw mulch under membrane on growth characteristics and yield composition of cucumber in greenhouse showed that the order of water consumption of cucumber in each growth stage was as follows:fruiting peak stage>initial flowering stage>stretch tendril stage>end fruiting stage.The increase of straw mulching amount under the membrane and the decrease of irrigation quota were conducive to the decrease of crop water consumption,showing CK>S1>S2>S3>S4,and W1 was higher than W2.The main water consumption stage of cucumbers was the initial flowering stage and the fruiting peak stage,and the sum of the water consumption modulus was more than 75%.The water consumption intensity under straw mulching was W1>W2,which was significantly lower than CK.The crop coefficient increased first and then decreased,and showed W1>W2.The dynamics of plant height,stem diameter,leaf number and total dry matter accumulation with planting time could be accurately simulated by the Logistic equation,in which nRMSE and D were in the range of 1.98-19.84 and 0.94-1,respectively.Appropriate straw mulching was beneficial to the accumulation of dry and fresh matter in plants,and to the improvement of yield,irrigation water use efficiency,and irrigation water compensation rate.The highest yield treatment W1S3 was 74280.95 kg/hm2(2020)and 105237.78 kg/hm2(2021).which was significantly increased by 68.69%and 13.37%compared with CK(P<0.05),respectively.The principal component analysis and the TOPSIS model were used to analyze the comprehensive benefits of various indicators of cucumber,and both of them showed the treatment W1S3 was the best Therefore,the optimal combination of irrigation quota and straw mulch amount for autumn and winter cucumber in Ningxia solar greenhouse was as follows:under full irrigation,and straw mulch amount was 1.25 kg/m2. |
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