Evaluation On Water Utilization In Combination Of Carbon And Nitrogen In Winter Wheat-summer Maize Cropping System In The North China Plain

North China Plain is one most important area of cereal producing in China, and land use isdominantly arable with winter wheat and summer maize cropping system, which is of great significanceto national food security. Water shortage in North China Plain has been the main factor restrainingagriculture sustainable development, and optimizing management of water and fertilizer and improvingwater use efficiency are considered as two effective measures to the challenge. Organic fertilizer canimprove soil physical and chemical properties, retard water shortage, coordinate the contradiction ofcrop water requirement and soil water supply and improve water use efficiency. However, theinformation of various management concerning the effects of organic fertilizer rate, carbon and nitrogencombination on soil moisture dynamic, water consumption and water use efficiency were remainlimited.Two experiments of inorganic fertilizer and organic fertilizer and water, carbon and nitrogencombination micro-plot were conducted in Lingxian county and Huantai county, respectively. In orderto check the effects of inorganic fertilizer and organic fertilizer,19treatments were designed withthree replicates, which were composed of2factors of inorganic nitrogen fertilizer and organicnitrogen fertilizer with10N levels of0,60,120,180,240,300,360,420,500,600kgN·hm^-2. Thewater, carbon and nitrogen combination micro-plot experiment was designed6treatments in a certainrate of N fertilizer, including （1） normal irrigation （each time with100mm）+inorganic N fertilizer(wheat,200kgN·hm^-2; maize,152kgN·hm^-2)（W1C0N2）;（2） normal irrigation+inorganic Nfertilizer (wheat,100kgN·hm^-2; maize,76kgN·hm^-2)+organic N fertilizer (wheat,100kgN·hm^-2;maize,76kgN·hm^-2)（W1C1N1）;（3） normal irrigation+organic N fertilizer (wheat,200kgN·hm^-2;maize,152kgN·hm^-2)（W1C2N0）;（4） decrement irrigation （each time with50⁶0mm）+inorganicN fertilizer （W2C0N2）;（5） decrement irrigation+inorganic N fertilizer+organic N fertilizer（W2C1N1）;（6） decrement irrigation+organic N fertilizer （W2C2N0）. We studied the dynamicchanges of soil annual moisture, crop water consumption, yield and water use efficiency during winterwheat and summer maize growing stage, and aimed to provide theoretical basis for improving waterand nutrient use efficiency. Our major conclusions were described as following:1. Under the same irrigation and N level, soil carbon can improve the capacity of soil waterstorage in rainy season and soil water conservation in dry season, and also decrease significantlywater losses during rotation, whilst an obvious effect was observed for soil water of storage early anduse later. Compared to the treatments with inorganic nitrogen, soil water storage （0¹00cm） beforewinter wheat and summer maize sowing were increased in the treatments with organic nitrogen underthe same nitrogen levels, increasing by0.987%¹9.3%（2.44⁴5.6mm） and0.543%¹3.9%（1.30³0.5mm）, respectively. Compared to C0N2, C1N1also increased soil water storage （0¹60cm）at the early stage of winter wheat and summer maize sowing, and the ranges were2.93%⁷.56% （12.1³1.6mm） and1.73%³.94%（7.17¹4.2mm）, respectively. Annual loss of soil water duringcrops rotation was varied from26.8to41.1mm （0¹60cm）, and the mean losses was1.58².42mm·d-1. The treatments with organic nitrogen decreased the annual loss of soil water losses duringcrops rotation compared to inorganic fertilizer, at11.5%²6.2%（4.73¹0.4mm）. The capacity of soilwater storage and soil water supply was improved in treatments with organic nitrogen, and it wassignificant correlated with soil aggregate, soil organic carbon and total nitrogen.2. Organic N fertilizer could improve water consumption and crop yield under low N levels, andinorganic N fertilizer showed similarly. The water consumption of winter wheat showed increasinglywith the carbon increase below a threshold value of199.4kgN·hm^-2(5293kgC·hm^-2), and similartrend was observed in inorganic N fertilizer with a threshold value of113.2kgN·hm^-2. Carbonapplication could improve winter wheat yield with the rate increasing below a threshold value of220.6kgN·hm^-2(5855kgC·hm^-2), and similar trend was found in inorganic N fertilizer with athreshold value of110.7kgN·hm^-2. Overall, the treatments of inorganic N fertilizer affected the waterconsumption and winter wheat yield more obviously than organic N treatments under low N levels.3. Under high N levels, crop yield and water consumption affected by increasing carbon but notobviously; organic N treatments obtained equal levels of crop yield and showed a better water-savingeffect compared to inorganic N treatments. No significant difference was observed for waterconsumption and yield when the organic N was over the rate of220.6kgN·hm^-2(5855kgC·hm^-2) orthe inorganic N was over the rate of113.2kgN·hm^-2. Compared to inorganic N treatments, organic Ntreatments showed an equal impact on winter wheat yield when the N rate was over220.6kgN·hm^-2,but water consumption was reduced by4.86%（21.1mm）; water use efficiency （WUE） was increasedby15.1%in organic N treatments when the N rate was over the value of372.0kgN·hm^-2(over thevalue of9874kgC·hm^-2). Overall, organic N treatments showed better water-saving effects underhigher N level.4. The optimum rates of organic N and inorganic N fertilizer were obtained from our results. Nosignificant difference was observed at the rates of110.7kgN·hm^-2and220.6kgN·hm^-2for organic Nand inorganic N fertilizer, respectively; and higher winter wheat yield and water use efficiency couldbe achieved at the rates of481.7kgN·hm^-2(12786kgC·hm^-2) and220.6kgN·hm^-2for organic N andinorganic N fertilizer. Therefore, organic N fertilizer rate of220.6⁴81.7kgN·hm^-2(5855¹2786kgC·hm^-2) and inorganic N fertilizer rate of110.7³67.6kgN·hm^-2were considered as the optimumfertilizer range. Compared to inorganic N fertilizer, the rate of organic N fertilizer increased by86.2¹14.1kgN·hm^-2(2288³029kgC·hm^-2), not only can obtain the equal crop yield, but alsoimprove water use efficiency.5. An optimal combination of water, carbon and nitrogen was ascertained based on our results.As a result, the treatment of W2C1N1was regarded as the most optimal management due to its bettercapacity of soil water conservation, crop growth characteristics, photosynthetic performance, and cropyield and water use efficiency.In conclusion, Organic N fertilizer application affected obviously on conserving water, reducing soil water losses, increasing yield and improving water use efficiency. However, the rate of yieldincreasing showed no significant difference at the over-high rate of organic fertilizer. Therefore, theoptimum range of organic fertilize is220.6⁴81.7kgN·hm^-2. Overall, W2C1N1was the most optimalin our designed experiment, because of its better growth characteristics, photosynthetic performance,and yield and water use efficiency.