Study On The Mechanism Of Spring Maize Field Water Consumption And Regulation Of Efficient Utilization Of Water And Fertilizer Under Ridge-Furrow Rainwater Harvesting Planting System

Dry farming areas in North China play an important role in ensuring food security.Agricultural production in this area is facing a shortage of water resources.At the same time,the unreasonable application of fertilizers results in low water and fertilizer use efficiency.The ridge-furrow rain water harvesting planting system is a cultivation technique widely used in dry farming areas in Northwest China,which can effectively improve the water use efficiency of crops.However,the mechanism of efficient water utilization is unclear.Determination the temporal and spatial distribution characteristics of root water in ridges-furrow rainwater harvesting system and quantification of evaporation and transpiration are the key to clarifying the mechanism of efficient water utilization,which is of great significance for optimizing the ridge-furrow ratio and making a reasonable fertilization plan to ensure the efficient utilization of water and fertilizer and sustainable development of dry farming.The field experiment on spring maize of this study carried out in a typical semi-arid agricultural area in Northwest China during 2018 and 2019,3 planting methods(RF40,ridge-furrow rainwater harvesting system with a ridge-furrow of 60:40;RF60,ridge-furrow rainwater harvesting system with a ridge-furrow of 60:60;FP,traditional flat planting as control)and 4 fertilization levels(H,high fertilizer with N 285+P₂O₅ 140 kg ha^-1;M,medium fertilizer with N 230+P₂O₅ 115 kg ha^-1;L,low fertilizer with N 175+P₂O₅ 90 kg ha^-1 and N,no fertilizer)were set.The experiment is based on the stable hydrogen and oxygen isotope technology,using the Iso Source model,water balance model and isotope mass balance model to study the spatial distribution of soil water and characteristics of root water absorption and field water consumption structure under ridge-furrow rainwater harvesting system.And analyze the soil water,the accumulation and distribution of dry matter and nutrients,the grain yield and the water and fertilizer use efficiency of spring maize regulated by ridge-furrow ratio and fertilization rates.The main results obtained are as follows:1.Spatio-temporal heterogeneity of soil water and root response characteristics in spring maize fields under the ridge-furrow rainwater harvesting planting system(1)The ridge-furrow rainwater harvesting planting system changed the symmetrical soil water distribution on both sides of the plants,and significantly increased the soil water content(SWC)in the shallow soil in the furrow,which promoted the growth of roots in the shallower soil in the furrow,and this difference of water distribution also stimulated the root system under the ridge expands into the deep soil.In the RF60 planting pattern,the root length density(RLD),root surface area(RSA)and root dry weight(RDW)in the 0-40 cm soil layer in the furrow are 56.5%,62.0%and 24.3%higher than those under the ridge in the jointing stage;that is 43.2%,56.9%and 16.9%in the tasseling stage.Compared with FP,RF40 and RF60improved the soil moisture status and increased the RLD,RSA and RDW of each soil layer,and the increase gradually decreased with the depth of the soil layer.In the jointing stage,compared with FP,RF40 and RF60 significantly increased the RLD in the 0-20 cm soil layer by 27.7%and 25.6%,and that in the 20-40 cm soil layer was 29.0%and 15.2%.Compared with FP,RF40 and RF60 significantly increased RLD of 8.8%-34.6%in 0-20 cm,20-40 cm and 40-60 cm soil layers during tasseling and filling stage.(2)It is different in root distribution and root water absorption in different root zones.Under the RF60 planting pattern,the root water absorption of each root zone is different.In the jointing stage,the root in the three root zones under the ridge,the junction of the ridge and the furrow,and in the furrow all absorbed soil water in the 0-20 cm soil layer.In the tasseling stage,maize root absorbed water mainly from the 0-20 cm soil layer,followed by the 20-40cm soil layer.During the filling stage,the roots under ridges and at the junction of ridges and in the furrow mainly absorbed soil water from 40-60 cm soil layer,with an average contribution of 69.3%and 65.7%,respectively;the roots in furrows mainly absorbed water from 40-60 cm and 20-40 cm soil layer,with the average contribution of 38.8%and 42.0%,respectively.The contribution of shallower soil layer to root water absorption under ridges is lower than that of other root zones,therefore,more water was absorbed from the shallower soil layers.There is a significant positive correlation between the contribution of soil water to maize root water uptake and the proportion of root distribution.(3)Different ridge-furrow ratios changed the spring maize root distribution,which resulted in differences in root water absorption under ridge-furrow rainwater harvesting system.In the jointing stage and tasseling stage,maize under all treatment absorbed water mainly from 0-20 cm and 20-40 cm soil layer,respectively.In the filling stage,there were some differences in the main water uptake soil layer under different planting patterns.The maize root under RF40 and RF60 mainly absorbed soil water from 40-60 cm,and the average contribution of this soil layer were 77.4%and 70.8%respectively;while the maize root under FP mainly absorbed soil water from 60-80 cm,the average contribution of this soil layer was78.5%.In the jointing stage and tasseling and silking stage,spring maize under the three planting patterns mainly absorbed water from the same soil layers,while in the filling stage,compared RF40 and RF60 the FP treatment absorbed water from deeper soil.2.Characteristics of evapotranspiration structure of spring maize field under ridge-furrow rainwater harvesting system(1)Planting patterns significantly affect the soil moisture status,and the SWC varied significantly in soil layers during the growth period.Compared with FP,RF40 and RF60significantly increased SWC of each soil layer before sowing and in jointing stage,and there was no significant difference between RF40 and RF60.It is the critical water demand period of maize after jointing stage to the early filling stage,and the maize consumes a lot of water.Therefore,there were no significant differences in SWC during the tasseling stage and the filling stage between all treatments.(2)The analysis of quantification of evaporation(E)and transpiration(T)by the stable isotope technique showed that the trend of T during the growth period increased firstly and then decreased with the growth stage advanced.The maximum T Appears in jointing to tasseling stage(60-90 days after sowing),followed by tasseling to filling stage(90-120 days after sowing).At sowing to jointing stage(0-60 days after sowing),water is mainly consumed in the form of E.Compared with FP,RF40 and RF60 significantly improved T and T/ET in the growth period.During the whole growth period,compared with FP,RF40 and RF60increased T/ET by 30.9%and 26.3%.In 2018,There were no significant difference in the T and T/ET between RF40 and RF60 in 2018,but RF40 was significantly higher than RF60 in2019.3.The regulation of ridge-furrow ratio and fertilization on efficient water and fertilizer utilization of spring maize under ridge-furrow rainwater harvesting system(1)Ridge-furrow rainwater harvesting system with all different ridge-furrow ratios significantly increased the dry matter accumulation of spring maize during all growth stages,and the nitrogen and phosphorus accumulation in all organs of maize during maturity stage,and the increase in the grain is the greatest.The dry matter accumulation of spring maize under RF40 is significantly higher than RF60,about 3.8%-6.8%higher.RF40 has a more obvious advantage over RF60 especially at the no fertilization level,with an increase of 18.0%.The increase of dry matter accumulation of spring maize in each growth period by fertilization under the rainwater harvesting planting patterns were lower than that of the FP.Dry matter is mainly distributed in the grains during the maturity stage.Ridge-furrow rainwater harvesting system and fertilization significantly increased the dry matter,nitrogen and phosphorus distribution in the grains,and the increase rate decreased with the increase of fertilization rate.The interaction of planting patterns and fertilization has a significant impact on maize dry matter,nitrogen and phosphorus accumulation in all organs and distribution in grains.(2)Both RF40 and RF60 significantly increased the number of kernels per ear,100-kernel weight,grain yield and biomass yield,and the grain yield and biomass yield under two ridge-furrow rainwater harvesting planting patterns increased by an average of 63.5%and 48.6%,respectively.As the fertilization rate increased,the differences between planting patterns gradually decreased.Fertilization also significantly increased the grain yield and biomass yield of spring maize,and the increase of the fertilization level of H was the greatest and increased by an average of 6.5 times and 4.6 times compared with that of N.The effect of ridge-furrow ratio on the grain yield and harvest index was different in two years,there was no significant difference between RF40 and RF60 in 2018,while RF40 significantly higher than RF60 in2019.The low temperature and excess rain during the filling stage of spring maize in 2019resulted in a significant reduction of grain yield and harvest index compared with 2018.(3)The ridge-furrow rainwater harvesting system with two ridge-furrow ratios significantly improved water use efficiency(WUE),precipitation use efficiency(PUE),the partial factor productivity(PFP)and agronomic efficiency(AE)of nitrogen and phosphate fertilizers.RF40 and RF60 increased WUE by 62.1%on average,increased PUE by 63.2%on average,increased PFP and AE of N fertilizer by 56.4%and 51.6%on average,increased PFP and AE of P fertilizer by 55.6%and 50.4%on average.There was no significant difference in WUE,PUE,PFP(N),AE(N),PEP(P),and AE(P)between RF40 and RF60 in 2018,and RF40 was significantly higher than RF60 at all fertilization levels in 2019,with an average increase of 24.3%,23.5%,14.7%,9.8%,14.8%,and 9.4%.(4)With the increase of fertilization rate,the WUE and PUE under all planting patterns have been continuously improved.Under each planting pattern,PFP and AE both increased firstly and then decreased with the increase of fertilization level,and reached the highest value at M fertilization level.Compared with the H fertilization level,the M fertilization level increased PFP and AE of nitrogen fertilizer were 7.7%and 5.0%,respectively,and increased the PFP and AE of phosphorus fertilizer are 5.8%and 3.2%,respectively.Compared with the L fertilization level,the M fertilization level increased PFP and AE of nitrogen fertilizer 4.9%and 13.1%,respectively;and increased the PFP and AE of phosphate fertilizer to 7.9%and16.4%,respectively.The research on spatio-temporal heterogeneity of soil water and root response characteristics and in evapotranspiration construction characteristics of spring maize fields based on the stable isotope technology found that the ridge and furrow rainwater harvesting planting system significantly improved water use efficiency.Under the ridge and furrow rainwater harvesting planting system,the maize root mainly absorbed water from the shallow soil in the furrow,and from the deep soil under the ridge,and the main water uptake layer was shallower than FP,thereby reduced soil evaporation synergistically with plastic film mulch,increased plant transpiration synergistically with soil water,and ultimately improving water use efficiency.By optimizing the ridge-furrow ratio and the amount of fertilization applied,the spring maize yield and water and fertilization use efficiency under the ridge-furrow rainwater harvesting system can be improved.In a comprehensive analysis,the greatest fertilizer use efficiency under RF40 was reached at a medium fertilizer level,and maintain spring maize field at a high yield and efficient water utilization at a stable state.Therefore,RF40 with N 230+P₂O₅ 115kg ha^-1 is recommended as an appropriate cultivation and management measure to efficiently use water and fertilizer and ensure sustainable development in this semi-arid region.