| Plastic film,straw and sand-gravel mulches are commonly used in farmland practice,which can greatly reduce the loss of soil surface moisture evaporation,improve soil temperature,and promote the increase of crop yield and quality.But at present,the results related to the effects of direct water control on soil water heat and the growth process of summer maize have not been compared.Different mulching techniques,i.e.,plastic film,gravel-sand and straw,have been applied in China for many decades,but have not been compared systematically for effects on soil water storage,evapotranspiration,crop growth,yields and water use efficiency?WUE?various crop growth stages.A Two-year summer maize growth experiment was conducted in containers under a rain-shelter to analyze the effects of plastic film,gravel-sand and straw surface mulches on soil water dynamics and crop growth processes.A lysimeter was designed for each container to dynamically measure soil-plant water dynamics.Eight treatments were designed including a control?no mulching-CK?,two straw mulch treatments with chopped-straw-length of 1mm?ST1?and 100mm?ST100?,black plastic-film-mulch?BPF0?,transparent plastic-film-mulches?TRPF0?,1-mm-straw below black plastic film?BPF1?,1-mm-straw below transparent film?TRPF1?,and 69 kg/m2gravel-sand-mulch?SAND?.24sets of high-precision lysimeter observation systems which established by under-ground soil columns and weighing sensors were used to observe the dynamic changes of soil moisture.In order to determine whether the meso-scale lysimeter observation system could truly and accurately reflect the change of soil temperature in the field,the soil temperature of the above-ground?the buried meso-scale lysimeters observation system and the field were compared and analyzed.At the same time,based on the data of two-year summer maize experiments,the original Shuttleworth-Wallace model and the improved one were used to simulate the summer maize evapotranspiration under the condition of plastic film mulching,and compared them with the measured values.By analyzing the differences of soil moisture,summer maize growth and evapotranspiration simulations under different mulching conditions,the following conclusions were obtained:?1?The trend of soil temperature?minimum,maximum and average soil temperature?observed at four different times of each year were similar in the above-ground,and fields for in the two years.However,the minimum,maximum and average temperatures of the soil in the buried lysimeters and field at four different times were similar for each day alone in2015.In 2015,the correlation of soil temperature?minimum,maximum and average soil temperature?between the buried lysimeters and the field was good,especially at 8:00,the correlation was much better than that between the minimum soil temperature for above-ground lysimeters and the field,but the correlation decreased slightly at 14:00 and 18:00.For the maximum daily variation of soil temperature in profile,the reduction accuracy of the buried lysimeters for field was higher than that of the above-ground lysimeters.In general,the restoration for the field of the minimum,maximum and average soil temperatures in the above-ground lysimeters were not very good,but still in a reliable range.And the restoration for the field was better by the buried lysimeters as a whole.?2?The results revealed that,all 7 mulching treatments decreased soil water evaporation during early crop growth stages.For the 2015 and 2016 growing seasons,average soil water storage during the jointing stage increased 32%,39%,48%,57%,61%,62%and 66%,yield increased 13%,18%,23%,28%,29%,34%and 29%,and WUE increased 1.4,2.1,3.0,3.2,3.5,4.1,and 3.6 kg·hm-2·mm-1 compared with the CK treatment,for the ST100,SAND,ST1,TRPF0,TRPF1,BPF0 and BPF1 treatments,respectively.In general,yield and WUE increases were greatest in the BPF0 treatment,followed by TRPF1,BPF1,TRPF0,ST1,SAND and ST100.Yield and WUE increases in the ST100 and SAND treatments were small.This research revealed that plastic mulch had the largest yield and?water use effiency?WUE increase,of which,black plastic film was better than transparent plastic film.The yield and WUE increase of gravel-sand-mulching was larger than 100-mm-in-length-straw-mulching but less than 1-mm-in-length-straw-mulching.?3?The daily evapotranspiration simulated by the SW model before and after the adjustment under the condition of black and white plastic film mulching is higher than the measured evapotranspiration in the early and late growth stage of summer maize in 2015 and2016.In the middle growth stage of summer maize,the evapotranspiration simulated by the two models was similar to the measured value,but most of the time the original SW model still overestimated the evapotranspiration,and the evapotranspiration obtained by the improved SW model during the whole growth stage of summer maize had strong consistency with the measured value.It could be seen that the adjusted SW model significantly improves the simulation accuracy of evapotranspiration.Both the original SW model and the adjusted SW model simulated evapotranspiration well in the rapid growth period of summer maize,and both models overestimated evapotranspiration in other growth periods,but the simulation accuracy of the adjusted SW model was much higher than that of the original SW model.The daily evapotranspiration values obtained from the adjusted SW model in 2015 and 2016 were well distributed along the 1:1 straight line,and the correlation coefficients were 0.88 and 0.87respectively,the determination coefficients were 0.86 and 0.88 respectively,and the consistency index were 0.87 and 0.89 respectively,indicating that the simulation effect of the improved SW model is reliable. |
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