| Efficient irrigation and nitrogen management techniques have made great achievements which have decisive roles in solving agricultural water shortage,efficient utilization of fertilizer and food requirement issues.However,amounts of questions of paddy soil such as soil cracking,preferential flow and ammonia volatilization,as well as non-simultaneous management between nitrogen(N)supply and plant requirement should be stressed due to severe soil water stress and excessive N input.Benefits of zeolite(Z)in water and N retention have created interest in enhancing water and N uptake to improve water-N use through lessening ammonia volatilization,lowering the risks of preferential flow and soil cracking.What is more,Z in paddy soil is easily extended due to its ease of operation,high treatment efficiency,no sludge production,small area occupied by the plant and relatively low investment costs.Therefore,based on features of higher water-NH4+ absorption capacity and environment-friendly application of Z,4-year experiments with lab trials were conducted to detailedly processively study the effects of Z addition into paddy soil on water-N regulation,root morphology and activity,water-nitrogen unptake and yield formation process.Along with the processive content,the article determined the Z application method,efficient N managements with Z amendment and water-N coupling managements based on Z.Detailed and chaptered conclusions are as follows:i.Impact of Z addition on rice growth performance and water utilization.Under traditional fertilization regimes,Z80(<0.178mm)at 10t·hm-2 rate could comprehensively enhance rice leaf area index,effective tiller numbers,and plant height,but Z rate at 15t hm-2 could not further improve these items.The regulation that Z affected the rice growth performance was from No to N52.5 level,Z inhibited rice growth performance for its high absorption capacity while from N105 to N 157.5 level,Z input in paddy field could alleviate the inhibiting effects to enhance the growth characters.Under traditional fertilization regimes,Z application in paddy soil could dramatically increase rice grain yield by 10.1-15.3%,water productivity(WP)7.3-12.5%and effects of enhancement in yield and WP exhibited superior performance in water-saving irrigation regimes(Dry-wet Alternate Irrigation,AWD).In contrast to flood irrigation(IF),moderate dry-wet alternate irrigation(IM)and heavy dry-wet alternate irrigation(IH)respectively lowered the water consumption by 14.5%and 26.5%.With treatment of IM and IH,Z application at rice tillering stage and milky ripening stage could respectively save water input by 5.8%and 12.0%.However,at rice critical stage of water demands(Jointing-booting stage and heading-flowering stage),there was no water-saving effect and a statistically substantial increase in water consumption was observed in treatment of Z.ii.Impact of Z addition on controlled-release mechanism of water and nitrogen.From day 1 to 6 after applying urea with one-time input method,Z could accelerate the hydrolytic process of urea and then increase NH4-N content in a short time.From day 7 to 12,Concentratedly-applied N with Z as controlled-release N fertilizer(CRF1)could hold available NH4-N in exchanged size of Z and trigger N stress.From day 13 to25,Z amendment could desorb NH4-N and increase its content as well as NO3-N.From day 26 onward to day 45,in contrast to non-treated soil,there were significantly higher content of NH4-N and NO3-N.Hence,CRFi could impact the available N in soil for about 45 days.However,CRF3(third-split N fertilization with Z)could regulate the available N lasting to rice milky ripening stage.Compared to non-treated soil,Z at 7.5 and 15t·hm-2 on introduction into surface soil(0-30cm)could respectively enhance soil field capacity(FC)by 0.81%and 1.56%.When soil water potential changed from-lOkPa to-37kPa,the water content in soil treated by Z was significantly higher than that with non-treated soil.Consequently,the enhanced FC could regulate the soil water content and lower irrigation frequencies to save irrigation water at non-critical stage of water demand.However,at critical stage of water demands,the duration of soil moist status was short.Hence,Z tendentiously increased irrigation water due to the enhanced FC and higher evapotranspiration of rice.According to the dynamic changes of soil water content,potential of Z to save irrigation water is relatively large yet.?.Impact of Z addition on soil elements content and root system.The combination between AWD irrigation and Z could also improve rice essential nutrient elements such as K?Na and Ca in soil and hence further enhance rice production and WP.Under different water-nitrogen managements,Z could significantly enlarge root mian length,root volume,root dry matter and root activity associating with enhanced the ability of water-nitrogen transport to aboveground biomass to enhance water and nitrogen use efficiency.iv.Impact of Z addition on ability for N uptake of aboveground plant and yield formation process.Under different water-nitrogen managements,agronomic practice of Z amendment that took into account higher N uptake to alleviate N pollution into underground water could enhance the N content of rice root and grain but lower the N content of rice leaf and stem.The enhanced root system statistically clealy affect the N uptake and transport to aboveground biomass and eventually impact the formation process of rice grain yield.The mechanisms proposed to account for higher economic yield and stable grain filling process could also be that treatment of CRFi possessed characters of higher grain growth weight(2.12 g·100grain-1),active phase of grain filling(29.02 d)and lower maximal rice grain filling rate(0.11 g(100grain day)-1),average grain filling rate(0.073 g-(100grain day)-1).v.Lab experiment research on absorption-desorption mechnisms of Z.NH4+ exchanged by Z would be lessened by a power function with increase of Z dosage associating with addition of other ions such as Na+ through compete mechanism.However,NH4+ exchanged by Z could be improved through decreasing the amount of solution.In conclusion,combination between moderate dry-wet alternate irrigation(IM)and N157.5 with Z80 amendment(<0.178mm in size,5-10t·hm-2)could comprehensively improve rice grain yield and WP in paddy field.The management strategy having environment-friendly effects on groundwater for its higher N uptake,N use efficiency and N harvest index is the best production management strategy with features of water-saving,high rice grain yield,low labor force and enhanced nitrogen use efficiency. |
PDF Full Text Request