Effects Of Mulching Combined With Nitrogen Application On Soil Physico-chemical Properties And Potato Growth In Semi-arid Areas Of Southern Ningxia

Aiming at the spring drought in the rain-fed areas of southern Ningxia,the evaporation is strong,the application of nitrogen fertilizer is excessive,the waste is serious,and the utilization rate of water and fertilizer is low.In this study,different cover materials and nitrogen fertilizer use cracking zone tests were carried out in the dry area of southern Ningxia.The main factors of common mulch film(M1),water permeable degradation film(M2)and mulch film(M3).Nitrogen application rates of 120(low nitrogen application N1),180(conventional nitrogen application N2),240(medium nitrogen application N3)and 300 kg/hm2(high nitrogen application N4)were secondary factors,and the conventional nitrogen application rate was(M1N2)as a control,studied its effects on soil physical and chemical properties and potato yield and quality,providing a theoretical reference for high-yield potato cultivation in the southern mountainous areas of Ningxia.The main findings are as follows:(1)Covering combined nitrogen application has water storage and preservation effect on 0-100 cm layer soil.The soil moisture changes in the 0-100 cm layer under different treatments during the potato growth period decreased first and then increased,and decreased to the lowest during tuber formation.Under the same covering material,there were differences in the treatments at different growth stages.Under the different mulching materials,the M2 treatment significantly increased the soil water storage in the bud stage,tuber formation stage and tuber expansion period by 10.8%,12.1%and 28.1%,respectively.The M3 treatment increased significantly by 10.3%,10.7%,and 21.6%,respectively,compared to M1.The interaction between coverage and nitrogen application had a significant effect on the soil water storage during the whole growth period of potato.In all treatments,the soil water retention effect was the best under the coverage of water-degradable membrane+nitrogen application rate of 300 kg/hm2 and hemp film coverage+nitrogen application rate of 120 kg/hm2.The water-permeable degradation membrane covered+nitrogen application rate of 180 kg/hm2.The water-permeable degradation membrane covered+nitrogen application 240 kg/hm2 and the mulch film coverage+nitrogen application rate 240 kg/hm2 treatment,while the common membrane cover combined with each nitrogen application level had the worst water retention effect.(2)Covering combined with nitrogen application can regulate the soil temperature of 0-25 cm layer.The average soil temperature at each layer of 0-25 cm under all treatments during the growth period of potato showed a trend of decreasing continuously,and the seedling stage was the highest.Under the same covering material,there was no significant difference in the treatment of potato growth period.Under the different mulching materials,the average soil temperature with M2 treatment in potato seedling stage,bud stage,tuber formation stage,starch accumulation and harvest period was decreased by 8.6%,7.I%,5.2%,12.2%,and 15.4%compared with M1.M3 treatment was 19.0%,8.9%,8.6%,2.6%,16.0%,and 16.9%lower than M1,respectively.The interaction of the combined nitrogen application has a significant effect on the average soil temperature during the growth period of the potato.In all treatments,the treatment with mulch film+nitrogen application rate of 300 kg/hm2 had the best cooling effect,and the mulch film coverage+nitrogen application rate was 240 kg/hm2,while the common mulch film coverage+nitrogen application rate was 120 kg/hm2.And the common film cover+nitrogen application rate of 240 kg/hm2 treatment had a warming effect.(3)Covering combined nitrogen application had different effects on soil physical and chemical properties during the potato harvest.Water-permeable degradation film coating could improve>0.25 mm the mechanical stability aggregate content at 20-40 cm layer,soil available phosphorus,total phosphorus and organic matter content at 0-40 cm layer,while the mulch film cover could increase the soil available potassium,total nitrogen and organic matter content at 0-40 cm layer.Treatment with nitrogen application of 120 kg/hm2 could increase>0.25 mm the mechanical stability agglomerate content at 20-40 cm layer and soil porosity at 0-40 cm layer.The treatment of nitrogen application of 180 kg/hm2 could increase>0.25 mm Mechanical stability agglomerates,soil porosity,available phosphorus,available potassium,total phosphorus and organic matter content at 0-40 cm layer.Treatment with nitrogen application of 240 kg/hm2 could increase soil porosity,alkali nitrogen and available potassium content at 0-40 cm layer.Treatment with 300 kg/hm2 treatment could increase the soil alkaline nitrogen and total nitrogen content at 0-40 cm layer.(4)Covering combined with nitrogen application could increase nitrogen content in soil and plants.The contents of soil alkaline nitrogen,ammonium nitrogen and nitrate nitrogen in the 0-40 cm layer under different treatments decreased first,then increased and then decreased,and peaked at the seedling stage and tuber expansion stage.The content of soil alkaline nitrogen was the most significant with mantle film cover+nitrogen application rate of 240 kg/hm2,while the content of soil ammonium nitrogen and nitrate nitrogen was the best with mantle film and nitrogen application rate of 180 kg/hm2.The nitrogen content in leaves,stems and roots of potato under different treatments showed a trend of decreasing continuously.The seedling stage was the highest,the nitrogen content of tuber in potato growth period decreased first and then increased,and decreased to the lowest during the tuber expansion.Under the different mulching materials,the nitrogen content of stems,roots and tubers in M2 treatment was 24.4%,6.5%and 13.9%significantly lower than that of M1,respectively,while the content of nitrogen in leaf with M3 treatment was significantly increased by 4.3%and 14.0%,respectively.(5)Covering combined with nitrogen application could improve soil water and temperature environment,and promote potato growth and development.The plant height,stem diameter and aboveground biomass during the growth period of potato with the different treatments increased first and then decreased,and reached the maximum in the tuber expansion period.The treatment with water-degradable membrane and nitrogen application rate of 180 kg/hm2 was promoted significantly,and the potato growth was the best.The SPAD value in the main growth period potato with each treatment decreased with the growth period,and it was the largest in the bud stage.The treatment with common mulching film and nitrogen application rate of 120 kg/hm2 was the best.(6)Covering combined with nitrogen application could increase potato yield and water use efficiency.The treatment with water-degradable membrane and nitrogen application rate of 180 kg/hm2 was the best.The effect of covering and nitrogen application on potato quality was extremely significant.In all treatments,the quality of potato with mulch film coverage+nitrogen application rate of 180 kg/hm2 was the best,followed by the control,while the common mulch film coverage+nitrogen application rate 300 kg/hm2,water-seepage degradation fi]m coverage+nitrogen application rate 300 kg/hm2,hemp film coverage+nitrogen application rate 120 kg/hm2 and hemp film coverage+nitrogen application rate 240 kg/hm2 treatment effect was poor.