Effects Of Different Irrigation Regimes On Grain Yield,Water Use Efficiency And Nitrogen Use Efficiency Of Winter Wheat

The field experiment was carried out at Shandong Agricultural university, Tai’an,Shandong province, China (36°09′N,117°09′S) in the growing seasons of2009/2010and2010/2011. The experimental design was a complete randomized block design with threereplicates. The experimental winter wheat (Triticum aestivum L.) cultivars, Shannong15(SN15) and Tainong18(TN18), were sown on9and10October in2009and2010, respectively,at a seeding rate of270seeds m-2as part of a larger experiment. Four irrigation levels wereused:(1) W0, no irrigation was applied.(2) W2, irrigating at jointing and anthesis.(3) W3,irrigating at before-wintering and jointing and grain filling.(4) AFI (alternate furrowirrigation), irrigating at jointing, before-wintering and grain filling was alternately irrigatedbetween the two neighboring plot (one of the two neighboring plots irrigating before-wintering and jointing, the other one irrigating at jointing and grain filling.). Effects ofdifferent irrigation regimes on yield, water use efficiency, and nitrogen use efficiency ofwinter wheat were investigated. The main results are shown as follows:1The effects of different irrigation regimes on grain yield and its componentsWith the increase of irrigation, the spike numbers and kernel numbers of per spikeincreased, but1000-grain weight decreased in the treatments. The spike numbers in the AFItreatment was significantly higher than that of W2treatment with the same irrigation amount.1000-grain weight in AFI treatment was significantly higher than that of W3treatment.With increasing amount of irrigation, the grain yields increased. The grain yield intheAFI treatment was significantly higher than that of W2treatment, and there was nosignificant difference in grain yield between AFI and W3. The results indicated that the AFImethod could maintain the same grain yield as that of conventional irrigation with highirrigation amount. 2The effects of different irrigation regimes on water use efficiencyWith the increase of irrigation amount, total water consumption amount and ratio ofirrigation amount to total water consumption amount both increased significantly, but theamount of soil water was decreased. The variation coefficient of proportion of soil waterconsumption amount to total water consumption amount was significantly higher than that ofprecipitation to total water consumption amount, and this indicated that the regulation rangeof soil water use efficiency was relatively larger. The proportion of soil water consumptionamount to total water consumption amount of treatment AFI was significantly higher than thatof treatments W2and W3.With increasing amount of irrigation, the water use efficiency (WUE) decreased. The WUE oftrearment AFI was significantly higher than those of other irrigation treatments, whichirrigation water use efficiency was also rather higher. The results above indicated thattreatment AFI was the best irrigation treatment that got high yield and high efficiency.3Factors affecting water use efficiency of different irrigation regimesThe changes of water use efficiency (WUE) in different irrigated winter wheat plantingcould be attributed to amount of soil evaporation, photosynthetic characteristics, soil waterconsumption and physiological and biochemical indexes of flag leaf. In two growing season,from anthesis to maturity, the cumulative evaporation in treatmemt W0was significantlylower than that of other irrigation treatments. The difference in the total accumulatedevaporation of two cultivars was observed among different irrigation treatments with the rankof W3> W2> AFI. Results showed that soil evaporation is one of the important ways to soilmoisture loss, and alternate irrigation can reduce soil surface evaporation loss1/3, soilevaporation mainly through the loss of irrigation furrow. The alternate irrigation by reducingthe surface humid area can significantly reduce soil evaporation among plants.With the increase of irrigation water, soil water consumption of wheat growing season in0-200cm soil layer decreases. Soil water consumption in treatment W0was the highest, andtreatment W3was the lowest. The results showed that water deficit increased soil waterconsumption of wheat, and waterlog is not conducive to improving the use efficiency. Nosignificantly difference of the soil water consumption amount of0~60cm soil layer betweentreatments W2and AFI, and the soil water consumption amount of60~140cm soil layer intreatment W2was lower than that of treatment AFI. Alternate irrigation can make moreeffective use of soil water, especially in deep soil water storage, to improve water useefficiency.Photosynthesis water use efficiency (WUEphoto) in the whole grain filling stage decreasedgradually. Before irrigation at grain filling, photosynthesis water use efficiency in treatment AFI was significantly higher than that of treatment W2, and there were no significantlydifference between treatments AFI and W3. After irrigation at grain filling, photosynthesiswater use efficiency in treatment AFI was significantly higher than that of treatment W3. Theresults show that alternate irrigation method can keep the same photosynthetic rate, but canreduce the transpiration rate, thus can enhance photosynthesis water use efficiency.Compared to treatment W2, the same irrigation amount, the water potential, osmoticpotential and relative water content of flag leaf in treatment AFI was significantly higher thanthat of treatment W2; but there was no significant difference between treatments AFI and W3.The results suggested that alternative irrigation reduce the amount of irrigation, saving waterresources, and make the wheat flag leaves maintained higher water potential and osmoticadjustment ability.4The effects of different irrigation regimes on nitrogen use efficiencyThe total nitrogen accumulation amount of plant derived from fertilizer proportion is33.76%~40.49%, derived from soil proportion59.51%~66.24%. With the increasing ofirrigation amount, total nitrogen accumulation amount, nitrogen accumulation amount derivedfrom fertilizer and soil increased. Compared to treatment W2, the same irrigation amount, thederived from fertilizer amount in treatment AFI was significantly higher than that of treatmentW2, but there was no significant difference between treatments AFI and W3. The derivedfrom fertilizer proportion in treatment AFI was significantly higher than that of treatment W3.The results showed that alternate irrigation is more conducive to the absorption of nitrogenfertilizer, to improve the utilization rate of fertilizer nitrogen.With the increase of irrigation amount, the total nitrogen accumulation, nitrogenproductive efficiency and nitrogen uptake efficiency increased significantly, while thenitrogen use efficiency and nitrogen harvest index decreased. The total nitrogen accumulation,nitrogen productive efficiency and nitrogen uptake efficiency in treatment AFI weresignificantly higher than that of W2treatment, the nitrogen use efficiency and nitrogenharvest index in treatment AFI were significantly higher than that of treatment W3. Theresults showed that the alternate irrigation increased N uptake efficiency, nitrogen harvestindex and nitrogen fertilizer production efficiency, promote the wheat to nitrogen uptake andutilization and to the distribution of grain, energy utilization rate of the relationship betweengrain yield and nitrogen in wheat, obtain high yield and high efficiency.With increase of amount irrigation, the soil NO3--N content of irrigation treatments in0~200cm soil layer gradually reduces with increasing the soil depth. In the same irrigationamount,0~200cm soil NO3--N accumulation in treatment AFI was significantly higher than that of treatment W2. With increasing amount of irrigation, the soil NO3--N content ofirrigation treatments in0~100cm soil layer significantly reduces with increasing amount ofirrigation, but increases in varying degrees in100~200cm.0~100cm soil NO3--Naccumulation in treatment AFI was significantly higher than that of treatments W2and W3. Itshowed that, alternate irrigation reduce the content of soil NO3--N leaching from0~100cmsoil layer to100~200cm soil layer.