| Farmland of cinnamon soil in Shanxi Province amounts to2.861millionhm2, which accounts for54.9%of the total arable land area in Shanxi and playsa very important role in the agriculture of the province. Cinnamon soil in Chinais mostly distributed in rainfed agricultural area with semi-arid or semi-humid,partial-drought types of the warm temperate zone climate. Drought is the mainconstraints to the sustainable development of the agriculture on rainfedcinnamon farmland, and to improve the precipitation use efficiency and wateruse efficiency of crops under the conditions of limited water resource availablehas become one of the important topics in dryland agriculture research.Mulching is an effective measure of soil conservative management in arid,semi-arid and semi-humid, partial-drought types of climate zones. Themoisture, fertility, permeability and heat conditions in the soil environment canbe regulated by combining mulching with conservative tillage,0-tillage anddeep scarification, thus to maintain the sustainable virtuous circling of soilenvironment quality and subsequently to stabilize and improve crop production.The work of this thesis was supported by the research projects including theNational Special Research Project in Nonprofit Sectors (Agriculture)(201203030-08-03), the National Science and Technology Plan in Rural Areaduring the Twelfth Five-year Plan (2012BAD09B01-1) and the Fund of KeyOpen Laboratory of Rainfed and water conservation Agriculture, the Ministry ofAgriculture, and is based on the long-term experiments conducted in theNational Experimental Zone for Tackling Science and Technology Problems of Rainfed Agriculture located in Shouyang County, Shanxi Province. In the thesis,the moisture, fertility, permeability and heat conditions at the interface betweencrop root and soil as well as the water conservation and crop productionimproving effectiveness were studied through the analysis of data of six variousmulching methods and control, i.e. water-permeability plastic film mulching+straw mulching between rows (SJ), water-permeability plastic film mulching (S),common plastic film mulching+straw mulching between rows (PJ), commonplastic film mulching (P), straw mulching between rows (J) and0-mulching(CK). The main results are as follows:1. Effect of different mulching methods on farmland soil moistureThe moisture gathering and evaporation inhibiting abilities of differentmulching methods varied, showing the largest disparity of soil moisture amongdierretn treatments mainly in the soil depth between0-60cm, and this disparityof water storage grew smaller with the increase of soil depth. The treatments ofPJ and P exhibited the best moisture gathering and evaporation inhibitingabilities in the soil depth between0-60cm and0-200cm, followed by thetreatment of J, SJ and S. In the soil depth of0-60cm, he average soil waterstorage of PJ, P, J, SJ and S over6years were increased respectively by12.71,9.78,8.03,3.43and2.66mm as compared to CK; and in the soil depth of0-200cm, he average soil water storage of PJ, P, J, SJ and S over6years wereincreased respectively by8.8,5.5,3.9,4.9and3.5%compared to CK, withincrements of38.03,23.45,16.91,20.96and15.17mm, respectively. There werelarge interannual differences of soil water storage among different mulchingtreatments. But in years of various precipitations, PJ and P could significantlyimprove the soil storage during the whole growth period of spring maize.The variances of soil moisture in deeper soil layer showed that plastic filmmulching and straw mulching presented obvious moisture gathering andevaporation inhibiting effects. Mulching with plastic film and/or straw drives thewater in deeper soil layer upward so that soil water content was increased andmoisture stored in upper soil layer. At the same time, mulching narrows the fluctuation of moisture in different depths of soil profile, thus ameliorates theimpacts of drought and lowers the soil moisture of root zone during floods, andsubsequently helps stabilize or promote crop production.2. Effect of different mulching methods on farmland soil temperatureThe geothermal temperature varied in different mulching treatments.Water-permeability plastic film (S) or common plastic film (P) mulching showeda heating effect, while straw mulching exhibited a temperature-regulating effect,which means a “cooling effect” at high atmosphere temperatures and a“warm-keeping effect” at low atmosphere temperatures.In this study, the changes of geothermal temperature at the soil depth of5cm as a function of time within24hours in different mulching treatments weresimulated, and the daily representation time point at different soil depths wasdetermined for different mulching methods. The changes of geothermalmaximum amplitude against time and soil depth were analyzed. It wasdiscovered that geothermal maximum amplitude decreased successively with theincrease of soil depth in all mulching treatments, which can be represented asexponential equations.The seasonal changes of geothermal temperature were also analyzed. In thewhole growth period of spring maize, the “heating effect” of S, SJ, P and PJtreatments and the “temperature-regulating effect” of J treatment were largeduring the early growth stages and became small during the later growth stages.Both effects abated gradually over time.3. Effect of different mulching methods on farmland soil nutritionDifferent mulching methods showed a large impact on topsoil total nitrogencontent, but did not exhibited significant effect on topsoil total phosphorous andtotal potassium contents. The treatment of J obviously increased soil organicmatter content; SJ and PJ treatments slightly improved soil organic mattercontent, whereas no changes were found in soil organic matter content of S andP treatments. Mulching increased the contents of available phosphorous, slowlyavailable potassium and alkali-hydrolyzable nitrogen. The treatment of J increased the rapidly available potassium content in topsoil, which was found tobe slightly reduced in other mulching treatments. The activity of soil enzymeswas sensitive to the changes of soil environment, and various activity values ofsoil urease, alkaline phosphatase and catalase were found in different treatments.Mulching reduced nitrogen accumulation in soil regardless of variousannual precipitations, but the accumulation occurred at different soil depths indifferent treatments. In dry years, mulching increased nitrate nitrogenaccumulation in the soil depth of0-100cm and effectively decreased itsaccumulation in deeper soil layer. In wet years, mulching increased nitratenitrogen accumulation in deeper soil layer and a proportion of fertilizer nitrogenwas leached away from the root zone of maize.4. Effect of different mulching methods on growth, production andwater use efficiencyAll mulching treatments brought forward the phonological periods ofspring maize, shortened the total growth period, but elongated the reproductivestages, which was conducive to the accumulation of solid matter in maize grains.Meanwhile, the emerging of maize seedlings was earlier and the canopy grewmore rapidly compared to0-mulching control due to the increase in geothermaltemperature in the early stages of growth after mulching, LAI and dry mattercontent of maize increased significantly in mulching treatments. Thephonological periods of maize were postponed in treatments with strawmulching as compared to control, but LAI and dry matter accumulation pickedup right after jointing stage when the temperature rose, and overtook those of0-mulching control. The dynamics of dry matter accumulation was inaccordance with that of LAI.All mulching treatments significantly improved maize production (p<0.05).There were differences of2.95-16.13t/hm2in grain production betweenmulching treatments and0-mulching control, with increments of5.29%-28.93%.There were differences in grain production of maize among the mulchingtreatments, and the annual average production of the treatments followed a sequence of SJ>S>PJ>P>J>CK. All mulching treatments significantly improvedwater use efficiency and precipitation use efficiency of spring maize. Of variousannual precipitations, both S and SJ treatments showed highest WUE and PUE,followed by P and PJ treatments, and J treatment exhibited lowest WUE andPUE. The average annual water conservation effectiveness of J, P, PJ, S and SJover6years was increased by52.76,157.76,183.30,230.60and252.19RMB/hm2respectively as compared to CK.The reasonable combination of straw and plastic film mulching effectivelyovercome their respective downside and significantly promotes growth,development and production of spring maize. In the present study,water-permeability plastic film mulching+straw mulching between rows (SJ)exhibited the best production improving capability with the highest WUE andsoil moisture storage and conservation effects. Water-permeability plastic filmmulching (S) showed less production improving capability and lower otherparameters tested, but with no significant differences to those of SJ treatment. SJand S represented best net profit and water conservation effectiveness. Strawmulching (J) showed less water storage and conservation effects, productionimproving capacity and lower WUE as compared to common plastic filmmulching+straw mulching between rows (PJ) and common plastic filmmulching (P) treatments, but showed better effects than CK. In addition, Jtreatment saves the investment of plastic film and labor, gives higher net profitand is in voidance of environmental pollution. Taken into account all theabove-mentioned research results, water-permeability plastic film mulching (S),water-permeability plastic film mulching+straw mulching between rows (SJ)and straw mulching (J) are suitable for application and extension in farmingpractice. |
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