Effects Of Rainwater Harvesting Patterns And Nitrogen Application Rates On Soil Water And Temperature Conditions And Crop Water And Nitrogen Uses

Precipitation shows great variability in arid and semi-arid region in northwest China where crop production is generally dependent on rainfall.At the same time,the quantities of nitrogen fertilizer applied in the agricultural production in northwestern China are often larger than the threshold levels.The main purpose of this study was to explore the effects of different rainwater harvesting patterns and nitrogen application rates on soil hydrothermal regimes,nitrate nitrogen distribution in soil,crop growth,nitrogen absorption,crop yield,and water and nitrogen use with a winter wheat/summer maize rotation system.To achieve these goals,field experiments were carried out at the Key Laboratory?108°24?E,34°20?N?of Agricultural Soil and Water Engineering in Arid and Semiarid Areas sponsored by Ministry of Education,at Northwest A&F University.The first experiment?from October,2013 to October,2016?contained four different rainwater harvesting patterns.They were ridge-furrow planting with transparent film mulching over ridge only?M1?,ridge-furrow planting with corn straw mulching over furrow only?M2?,ridge-furrow planting with transparent film mulching over ridge and corn straw mulching over furrow?M3?,ridge-furrow planting with black film mulching over ridge and corn straw mulching over furrow?M4?,and a control treatment of flat planting without mulching?CK?.The second experiment?from June,2013 to June,2016?consisted of conventional urea?U??at 0?U0?,80?U80?,160?U160?,and 240?U240?kg/hm²;40%applied as a basal fertilizer and 60%top-dressed at jointing stage?and controlled release nitrogen fertilizer?C??at 0?C0?,60?C60?,120?C120?,180?C180?,and 240?C240?kg/hm²;all applied as a basal fertilizer?with no nitrogen fertilizer application as a control?CK?.The results were as follow:1.Effects of rainwater harvesting patterns on soil water?1?The four rainwater harvesting treatments could significantly improve soil moisture in0¹00 cm layer.The treatments with mulching both over ridge and furrow were superior to the treatments with mulching either over ridge or over furrow.The M1 was superior to M2 in improving upper soil moisture,while M2 was superior to M1 in improving lower soil moisture.?2?In winter wheat seasons,the M4 was the best in reducing soil water consumption and total water consumption.In summer maize seasons,the M3 was the best in increasing soil water storage and reducing total water consumption.2.Effects of rainwater harvesting patterns on soil temperatureThe soil temperature effects of rainwater harvesting treatments were mainly in the early stage of crop growth and the differences among treatments decreased with the increasing soil depth.In contrast to no mulching,corn straw mulching over furrow could reduce soil temperature.Compared with transparent film mulching,black film mulching over ridge could reduce the temperature under film.3.Effects of rainwater harvesting patterns and nitrogen application rates on soil NO₃^--N?1?The four rainwater harvesting treatments could improve the average soil NO₃^--N accumulation in 0²00 cm soil layer during main crop growth stages.The increased degree was greater in the M3 and M4 than the M1 and M2.Compared with summer maize,the increased degree of NO₃^--N accumulation with four rainwater harvesting treatments was smaller in winter wheat seasons.?2?M3 and M4 had a greater infiltration depth of NO₃^--N than other treatments at crop harvest.Compared with winter wheat,the peak depth of NO₃^--N content among treatments was higher in summer maize seasons.?3?Compared with urea,the application of controlled release nitrogen fertilizer could significantly increase NO₃^--N accumulation in 0¹00 cm soil layers in the middle and late growth stages of winter wheat and summer maize.?4?In contrast to urea treatments,the NO₃^--N content of the controlled release nitrogen fertilizer treatments had less variation and the maximum NO₃^--N content were shallower in0²00 cm soil layer at crop harvest.Compared with winter wheat,the differences of peak value of NO₃^--N among treatments were smaller in summer maize seasons.4.Effects of rainwater harvesting patterns and nitrogen application rates on crop growth?1?Compared with CK,the four rainwater harvesting treatments could improve plant height,aboveground dry matter,root characteristic parameters,chlorophyll content and photosynthetic rate.The effect of M3 and M4 was the best in winter wheat seasons and summer maize seasons,respectively.?2?The four rainwater harvesting treatments could speed up the crop growth process from seedling stage to filling stage relative to CK.However,the duration of filling stage to maturity stage was greater in rainwater harvesting treatments than CK,except for the M1.The growth cycle of winter wheat and summer maize showed that M3 and M4 were significantly longer than other treatments.?3?The plant height,aboveground dry matter and root characteristics were significantly higher in nitrogen application rates than without nitrogen application treatment.However,these indexes increased first and then steady with the increasing nitrogen application rate.There was no significant difference in crop indexes between C120 and U160,and between U240,C180 and C240,respectively.?4?Compared with the flat planting without mulching and no nitrogen application treatment,the root length of winter winter and summer maize under different rainwater harvesting treatments and nitrogen application treatments were shallower.5.Effects of rainwater harvesting patterns and nitrogen application rates on plant nitrogen accumulation,distribution and diagnosis?1?The treatment of M3 and M4 was better in increasing the nitrogen accumulation of plant and fruit for winter wheat and summer maize,respectively.?2?Compared with urea treatments,the plant nitrogen accumulation of controlled release nitrogen fertilizer treatments were small in early crop growth and followed by an accelerated accumulation rate.?3?The critical nitorgen concentration and shoot dry matter of winter wheat and summer maize both under urea treatments and controlled release nitrogen fertilizer treatments fitted a power function.The curves were validated with data from another growth season and their performances were proved to be stable.Compared with winter wheat,the plant nitrogen accumulation for summer maize with the same nitrogen fertilizer type and nitrogen application rate was less.6.Effects of rainwater harvesting patterns and nitrogen application rates on crop yield and water and nitrogen use efficiency?1?The M1 in single mulching treatments and the M3 in dual mulching treatments were better in improving yield and water and nitrogen use efficiency in winter wheat seasons.The M2 in single mulching treatments and the M4 in dual mulching treatments were better in improving yield and water and nitrogen use efficiency in summer maize seasons.?2?The annual yield and annual water use efficiency of M3 and M4 were significantly higher than that of M1,M2,and CK.?3?Crop yield and yield components presented a trend of increasing and then decreasing along with the increasing nitrogen application rate.The yield of C80 and U240 in winter winter seasons and the yield of C120 and U160 in summer maize seasons were not significantly different from each other.?4?Combined with the regression analysis of crop yield,nitrogen application rate and plant nitrogen accumulation,and the nitrogen diagnosis results based on nitrogen nutrition index model and nitrogen accumulation deficit model,the appropriate nitrogen application rate of urea and controlled release nitrogen fertilizer was 160²25 kg/hm² and 120¹91kg/hm²,respectively,for winter wheat,and was 160¹82 kg/hm² and 120¹46 kg/hm²,respectively,for summer maize.?5?A single season nitrogen application rate of 160 kg/hm² with urea or 120 kg/hm² with controlled release nitrogen fertilizer was reasonable in the rotation system.Compared with U160 and U240,C120 and C180 could obtain the same annual crop yield and increase annual productivity of nitrogen fertilizer,annual nitrogen agronomic efficiency and annual nitrogen apparent efficiency,respectively.In summary,the four rainwater harvesting treatments play important roles in conserving soil water,promoting crop growth and nitrogen uptake,and increasing crop yield and water and nitrogen use efficiency.The treatment of M3 and M4 is the appropriate rainwater harvesting pattern for winter wheat and summer maize,respectively.The treatments of C180and U240 in winter wheat and the treatments of C120 and U160 in summer maize do well in promoting plant growth,increasing nitrogen uptake,improving yield and nitrogen use efficiency,and reducing NO₃^--N leach.Compared with U240 and U160,C180 and C120 can obtain statistically equivalent crop yield with reduced nitrogen application rate,respectively.These results have great significances for improving precipitation use,completing rainwater harvesting system,promoting the application of controlled release nitrogen fertilizer.