| The dryland farming plays a crucial role in food production.Most of the loess plateau is a typical arid and semi-arid region in China.Water and nutrient are the two most important factors limiting food production of this region.How to make efficient use of limited rainfall to improve the matching degree between rainfall and water demand for winter wheat,and to optimize the nutrient management is the key to realize the high yield and high efficiency of agricultural production in this region.As an efficient water-saving cultivation technique,the ridge and furrow?R?system is widely used in this area.However,the effects of fertilizer amounts and supplementary irrigation on winter wheat production under R system are rarely studied,and the regulation effects of R system on winter wheat based on the response of different soil water storage before sowing?SWSS?and rainfall in growign season are still unclear.In view of the above problems,this study carried out field experiments in ningnan mountain area for 5 consecutive years from 2012 to 2017.Two field experiments were set under two planting systems?R system and traditional bare planting system?B??with four fertilizer amounts treatments and three supplementary irriagtion treatments.In the fertilizer amount experiment,there were four fertilizer amounts:high,medium,low,and no fertilizer amount.In the supplementary irrigation experiment,there were three treatments,supplementary irrigation at the early growing stage?I1?,supplementary irrigation at both the early and late growing stage?I2?,and no supplementary irrigation during the whole growing stage?I0?.The main results are as follows:1. Effects of fertilizer on grain yield,and water and fertilizer utilization of winter wheat under R system?1?In the early growing stage of winter wheat,the R model can significantly reduce the soil water consumption and increase the soil water content,thus promoting plant growth and increasing dry matter accumulation.The accumulation of dry matter in R mode is bound to consume more soil water.SWC in R mode tends to be balanced with that in B mode at the heading stage,and then it is gradually lower than that in B mode.The R system can significantly reduce the consumption of soil water and increase the soil water content?SWC?,thus promot the plant growth and increase the dry matter accumulation in the early growing stage of winter wheat.Higher dry matter accumulation of R system is bound to consume more soil water.The SWC of R system tended to be balance with B system at heading stage,and then it is gradually lower than that in B mode.At high and low SWSS the water consumption of winter wheat during the whole growth period under R system was significantly increased by 2.7-7.5%and 4.9-7.9%compared with the B system,respectively.In addition,the increasing fertilizer amount also increased water consumption,and the trend was gradually obvious after returning stage.The excavation ability of fertilizer under high SWSS was obviously higher than that under low SWSS.?2?R system,SWSS,rainfall during the growing period,and fertilizer significantly promoted the net photosynthetic rate,stomatal conductance and transpiration rate of winter wheat at the heading and filling stages.The SWSS and rainfall conditions required to obtain the same high level of these photosynthetic characteristics under R system were lower than in B system.It was also found that the increase of R system on photosynthetic characteristics was higher under low SWSS than under high SWSS.Further more,fertilizer had more significant effects on photosynthetic characteristics in years with more rainfall during growth period.?3?The grain yield of Rsystem was 4.4-61.6%and 30.4-78.2%higher than that in Bsystem under high and low SWSS,respectively.The variation coefficient of the grain yield under R system?30.1%?was significant lower than that in B system,which may indicate certain yield stability.The number of spikes per hectare in R system was lower than that in B system,but the grain number per spike and 1000-grain weight were significantly higher than that in B system under high SWSS.However,the yield components in Rsystem were higher than that of B system under lower SWSS.The water use efficiency?WUE?of R system was significantly increased by 2.1-11.1%and 22.2-65.2%compared with B system under the high and low SWSS,respectively.The results of path analysis showed that the determation of the factors on the grain yield and its components of winter wheat were followed as SWSS>rainfall in early growing stage>fertilizer amount>rainfall in late growing stage,and the decision coefficients of the four factors on grain yield were 82.9%,14.4%,9.5%and7.3%,respectively.The number of spikes per hectare and grain yield of winter wheat was significant increase with the increasing fertilizer under high SWSS,but they were no longer significant increase after fertilizer amount reached the medium level under low SWSS.The grain number per spike and 1000-grain weight were significant increase with the increasing fertilizer amount under high and low SWSS,but the increase were not significant when fertilizer amount up to medium level.WUE of high,medium and low fertilzer amount in R system was 2.5-6.9%,3.2-7.2%,and 8.3-9.5%significant higher than that in medium,low,and no fertilizer amount under high SWSS,respectively.However,there was no significant difference between the WUE of high and medium fertilizer amount under low SWSS.?4?The nitrogen and phosphorus uptake of winter wheat at the flowering stage in R system was significantly increased by 7.2-60.3%and 16.7-70.1%compared with that in B system under high SWSS,respectively,and the incerase at maturlty were 6.7-51.3%and31.0-55.9%,respectively.The nitrogen and phosphorus uptake of winter wheat at the flowering stage in R system was significantly increased by 27.9-56.8%and 38.8-60.6%compared with that in B system under low SWSS,respectively,and the incerase at maturlty were 35.6-61.8%and 27.0-58.7%,respectively.The results showed that the nitrogen transport rate of R system was lower than that in B system,but the phosphorus transport rate was higher than that in B system.Both the nitrogen absorption efficiency?Nup E?and phosphorus absorption efficiency?Pup E?in R system were higher than that in B system,but nitrogen utilization efficiency?NUE?and phosphorus utilization efficiency?PUE?were lower than that in B system.With the increase of fertilizer amount the nitrogen and phosphorus uptake of winter wheat increased at flowering and maturity stage,and the increase was higher under high SWSS than low SWSS.With the increase of fertilizer amount the nitrogen transport rate decreased under higher SWSS,but the phosphorus transport rate was increased.Both the nitrogen and phosphorus transport rate showed an increasing trend with the increased fertilizer amount under low SWSS.Under the two planting systems,Nup E and NUE tended to decrease with the increase of fertilizer amount.2. Effects of supplementary irrigation with R system?RI?on grain yield,and water and fertilizer utilization efficiency of winter wheat?1?RI reduced 1/2 supplementary irrigation amount than BI?border irrigation?,so the water consumption and soil water content were lower than BI.The water consumption of RI1 and RI2 was significantly reduced by 5.0-10.1%and 9.3-13.2%compared with the corresponding BI treatment under high SWSS,and reduced by 9.4-10.1%and 14.5-24.1%under low SWSS,respectively.?2?The net photosynthetic rate,stomatal conductance,and transpiration rate of RI at two supplemental irrigation treatments were higher than those of corresponding BI.Through the analysis of SWSS,rainfall during growth period and photosynthetic characteristics,it was found that the required rainfall under RI to obtain the same high level net photosynthetic rate,stomatal conductance and transpiration rate was lower than BI.And it verified the water-saving potential of RI.However,the effects of SWSS on the photosynthetic characteristics of winter wheat at heading and filling stage were weaken,which indicate that the regulation effect of SWSS was limited in time and space.?3?RI reduced the number of spikes per hectare,but increased the grain number per spike and 1000-grain weight under high and low SWSS.The grain yield of RI1 was higher than that of BI1 by 1.4-4.5%and 1.9-4.6%under the high and low SWSS but the difference was not significant.The grain yield of RI2 was lower than that of BI2 under both high and low SWSS.In addition,the utilization efficiency of irrigation water of RI was significantly higher than that of BI,in which the IWUE of RI1 and RI2 significantly increased by102.8-109.2%and 86.5-94.9%compared with the corresponding BI treatments,respectively.Although RI with supplementary irrigation has a small effect on rainfall utilization efficiency,the RUE of RI0 is significantly higher than that of BI0,and the increase is greater under low SWSS.Under the high and low SWSS,the WUE of RI1 was 6.5-10.2%and 12.2-14.4%signifiant higher than BI1,RI2 was 4.7-10.3%and 6.8-16.9%signifiant higher than BI2,and RI0 was 5.2-6.2%and 27.2-35.2%signifiant higher than BI0,respectively,which indicate that RI had higher regulation effect on water use under low SWSS.The path analysis showed that SWSS had the maximum decision on grain yield of RI with the decision coefficients of 65.6%,followed by the rainfall in the early stage of growth with the decision coefficients of 36.0%;SWSS had the maximum decision on grain yield of BI with the decision coefficients of 57.1%,followed by the irrigation amount with the decision coefficients of 6.7%.The rainfall in the early stage of growth had the maximum decision on the number of spikes per hectare in RI,but in BI was SWSS.The factors with the maximum decision on the grain number per spike and 1000-grain weight in RI and BI systems were SWSS and rainfall in the late growing stage.?4?The absorption and transfer of nitrogen and phosphorus of RI1 and RI0 at flowering and maturity stages were significantly higher than those of corresponding BI treatments,but RI2 was lower than BI2,which indicate that excessive irrigation may limit the ability of winter wheat to improve nutrient absorption and transshipment under RI system.The pre-flowering nitrogen transfer rate of RI was lower than BI under high SWSS,but higher than BI inder low SWSS;the pre-flowering phosphorus transfer rate of RI was higher than BI under both high and low SWSS.Nup E and Pup E of RI1 and RI0 were higher than that of corresponding BI treatments,however,Nup E and Pup E of RI2 was lower than BI2.In a comprehensive consideration,the effect of R system on the growth,grain yield,and water use efficiency of winter wheat under low SWSS was more significant than that of high SWSS.To achieve the aim of high yield and efficiency,higher fertilizer amount(N 270+yield,while in years with lower SWSS?<310 mm?can reduce fertilizer amount(N 90+P2O560 kg ha-1)or no fertilizer.Therefore,on the base of soil water storage before sowing to determine fertilizer amount is an effective measure to increase crop yield,utilization efficiency of water and fertilizer under R system in semi-arid areas.On the basis of improving the utilization efficiency of rainfall,RI can maintain or even increase the grain yield of winter wheat with half of the irrigation amount of BI.Hence,less or no irrigation is an irrigation mode that improves the efficiency of rainfall and irrigation water,which minimizes the amount of irrigation water.It is a new technical approach to solve the shortage of agricultural water.It can also provide a theoretical basis for the extension of R system to irrigated areas. |
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