Influence Of Soil Moisture Limits And Water Nitrogen Supply On Tomato Growth Under Alternate Partial Root-zone Drip Irrigation And Its Impact On Environment

As a kind of alternate partial root zone irrigation,alternate partial root zone drip irrigation has great advantage in water-saving and can be easily applied in agriculture production.However,the current research on alternate partial root zones drip irrigation?APRDI?is very limited,and most of them are limited to water-saving and yield-increasing effects.In addition,there are few studies on the impact of APRDI on fruit quality,as well as on the migration and utilization of nitrate nitrogen in the soil under APRDI with different water and nitrogen supply.In this experiment,tomato was taken as the study material to explore the best soil water limitation for the alternate of irrigation from one side to the other side.In addition,the coupling effects of different water and nitrogen supply on tomato growth and its environmental effects were studied under APRDI by simulating soil columns and labeling ¹⁵N supplied as K¹⁵NO₃ to a certain level of soil depth.The outcome of this research is expected to provides theoretical basis and practical guidance for the regulation of fertigation in alternate root zone drip irrigation,and evaluate the fate of residual nitrogen in soil profile and its potential for absorption by plant and its movement and loss from the root-zone.The main research results are as follows:?1?The first test sets up two irrigation methods:conventional drip irrigation and alternate drip irrigation.And three different soil moisture limits:80%?_??70%?_??60%?_??field capacity,?_??,two irrigation amount:high and low irrigation,total 8treatments.Test results found:Under the same amount of irrigation,compared with conventional drip irrigation,the root system has a stronger promoting effect when the lower limit of moisture control by alternate drip irrigation is 70%?_?;the aboveground part shows that the plant height has a different degree of reduction,the stem diameter is obviously thickened when the lower limit of moisture is 80%?_?and 70%?_?,and it is relatively thin at 60%?_?,and the total biomass is not significantly different under high irrigation volume,but significant decline in low irrigation volume.The leaves exhibited the highest chlorophyll content with a lower moisture limit of 70%?_?,but no significant decrease in photosynthetic rate,but the transpiration rate decreased significantly with low irrigation.The activities of protective enzymes such as SOD,POD,CAT activity and Pro content in leaves were strong when the lower limit of moisture was 70%?_?,which made the plants have the greatest effect on the resistance to adversity.The content of hormones in leaves during an alternate cycle also showed some regularity:with the extension of irrigation time,the lower limit of moisture content decreased,and the ABA content in leaves showed an upward trend,whereas IAA,ZR,and GA₃decreased overall.Leaf N,P and K concentrations and nitrate reductase?NR?activity also showed a significant increase in the lower limit of control moisture at 70%?_?,a significant decrease at 60%?_?,and a controlled lower limit of moisture of 70%?_?,significantly increased tomato yield,improved water use efficiency,and improved tomato quality,and alternate drip irrigation can significantly reduce nitrate-nitrogen leaching in the soil,save nitrogen resources,and reduce environmental risks.Under the reduced irrigation volume,compared with the corresponding high irrigation volume treatment,tomato root growth was significantly inhibited,the decline in plant height increased,the stem diameter further decreased,and biomass decreased significantly.When the lower limit of moisture is 70%?_?,the content of leaf chlorophyll decreases significantly,but the decrease is relatively small.The decrease of photosynthetic rate is lower and the transpiration rate decreases significantly.The activities of protective enzymes in leaves increased as a whole,and the protective enzyme activity was highest when the lower limit of moisture was 70%?_?,and the content of hormones in leaves also showed a significant increase with the prolongation of irrigation time,and the contents of IAA,ZR,and GA₃ continued in general.The N,P and K concentrations and the NR activity of the leaves decreased as a whole,but the decrease was smaller at the N,P and K concentrations,and the NR remained at a higher activity.At the same time,when the lower limit of moisture was70%?_?,the yield was not significantly lower than that of the CH80 treatment,the water use efficiency was significantly improved,and the fruit quality was significantly improved.In summary,comprehensive consideration of the influence of the lower limit of soil moisture on tomato growth,physiological response,quality improvement and environment,etc.,the alternate drip irrigation when controlling the lower limit of soil moisture at 70%?_?is the more suitable condition of alternation of tomato water.?2?In experiment two,two kinds of irrigation methods:conventional drip irrigation and alternate drip irrigation,were provided.The three types of high water,medium water,and low water irrigation,and the two kinds of nitrogen application,high nitrogen and low nitrogen,consisted of 6 treatments.By simulating soil columns,¹⁵N-labeled K¹⁵NO₃ was applied to certain layers of soil to study the effects of different water and nitrogen supply on tomato plant growth and ¹⁵N migration and utilization of soil profile residue under drip irrigation in alternating root zone.The following conclusions were obtained:Under the same nitrogen,compared with conventional drip irrigation,alternate drip irrigation significantly promoted root growth,and the fruit dry weight,total biomass,NPK absorption of leaves and total N uptake of plants were significantly increased at high irrigation volume.When the irrigation volume decreased by 31.39%,the root growth was not significantly inhibited by AMH treatment.The total biomass decreased by only 5.82%.The decrease of nitrogen,phosphorus and potassium absorption in the leaves was small,and the nitrogen uptake of fruits and plants did not decrease significantly.When the irrigation volume decreased by 47.19%,the root growth was significantly inhibited by ALH treatment,and the dry weight of fruits and total biomass were significantly reduced.The N,P and K uptake in the leaves and total nitrogen uptake in the plants were significantly reduced.When nitrogen was reduced by half,under the same irrigation volume,the growth of roots was inhibited when compared to the corresponding high nitrogen treatments,and the dry weight of fruits and total biomass were significantly reduced.The N,P,K uptake of the leaves and total N uptake of the plants were significant decline.¹⁵N mark in the 30-40cm soil layer,alternating drip irrigation treatment than conventional drip irrigation ¹⁵N migration distance of less than 10cm,and alternate drip irrigation more upward migration,less leaching,while the conventional drip irrigation is more leaching,the lower amount of irrigation,the lower the downward migration.The cumulative amount of ¹⁵N marked by alternate drip irrigation was significantly higher than that of conventional drip irrigation,while the nitrogen loss was significantly decreased,the lower amount of irrigation treatment,the lower the loss of nitrogen.In summary,the reasonable supply of water and nitrogen under alternating drip irrigation significantly affects the growth of crops,and under certain water stress,alternating drip irrigation increases the production effect more significantly,and the water-saving effect is more significant alternate drip irrigation can remarkably reduce the leaching of nitrate nitrogen in soil and reduce nitrogen loss,which will be of great significance to the efficient use of water and nitrogen resources,regulate the effectiveness of soil nutrient resources and reduce environmental risks.