| Gravel mulching is such an indigenous field technology and has been used for improve crop production for over 300 years in the Loess Plateau of Northwest China for many years.A number of studies performed both at home and abroad have shown that cover soil with gravel has a significant effect on water conservation and soil warming as well as crop production in arid and semi-arid regions.However,systematic field studies concerning its effects on soil hydrothermal environment and crop yield are insufficient.Moreover,agriculture has been considered one of the contributors to GHG emissions,and its contribution continues to increase with an increase in crop production.As a global strategy to mitigate climate change and enhance agricultural sustainability,greenhouse gas(GHG)emissions and carbon footprint(CF)are expected to decrease due to the impact of field practices.Both the GHGI and CI are poorly understood,with particularly limited study in dryland cropping systems.Studies should also focus on its potential influences on GHG emissions mitigation and agroecosystem carbon balance.Therefore,a 2-yr field experiment was conducted during the two consecutive cycles of Wheat-Maize cropping system in the Yangling District of Northwest China,to reveal the effects of gravel mulch on soil moisture,soil temperature,rain-fed crop growth as well as yields.Based on the above,we also monitored greenhouse gas emissions to assess the mitigation potential of gravel mulching on greenhouse gas emissions and carbon footprint.In addition,multi-level water productivity and crop productivity is also an important part in our research,to clarify the mechanism by which gravel mulching produces more crop and ecosystem production with less water and thus aid in optimizing gravel mulching technical parameters.Furthermore,this study can be regarded as a basic case to assess the influence of gravel mulching on ecological effects and agricultural water management.The main conclusions obtained in this paper are given as follows:(1)The results showed that,soil moisture was significantly and positively correlated with different gravel mulching degree,abbreviated as GMD.Compared with the control,soil volumetric moisture content increased with the increase of GMD,100% of surface gravel mulch treatment obtained the maximum soil water storage(△W).Results also showed that,gravel mulching acted as a water capacity layer,which not only reduced water loss in drought period,and guarded rainfall not been reduced by runoff in wet period.Both the ability of water containing in dry period and the rainfall interception ability in rainy period were calculated by the formula presented in this paper.Second,gravel mulching has an effective effect on soil temperature conservation,the daily average soil temperature in different depth of the four gravel mulch treatments were all higher than the control,and 100% gravel mulch was the maximum.To study how gravel mulch affected soil temperature and the difference in hot weather period and cold weather period,we plus tested the soil temperature in extreme coldest and hottest weather conditions during the wheat and maize growing season.Overall,in this study gravel mulching acted as a regulator of soil temperature,thus soil temperature can actively respond to extreme cold or hot weather.In extreme cold period,air temperature was around-5℃ to 0℃,soil temperature of GM4 was 5℃ higher than CK,and soil temperature of the other three gravel mulch treatments were all higher than CK;in extreme hot period,air temperature was around 40℃ to 45℃,soil temperature of GM4 was 3.7℃ less than CK,and soil temperature of the other three gravel mulching treatments were all less than the CK.Soil warming ability responded to air temperature and soil moisture were significantly different,the four gravel mulch treatments were all higher than the control treatment,and 100% gravel mulch treatment was maximum,gravel mulch could well insulated the soil temperature so it doesn’t grow too much of fall too fast.(2)Study the effects of gravel mulch on crops growth and yields,plant height and leaf area index were not significant different in winter wheat growing season,while in summer maize growing season,plant height and leaf area index of the four gravel mulch treatments were all significant higher than the control,and the 100% gravel mulch treatment was maximum.Study also showed that,wheat and maize yields increase with the increase of GMD,the average winter wheat or summer maize yields of the 2 growing seasons of 100% gravel mulch treatment were 15.34% and 26.66 respectively higher than the control.Moreover,system yield improved by 19.87% and 15.59% by applying 50 mm irrigation,53.58% and 43.18% by applying gravel mulching and 60.64% and 48.28% by applying gravel mulching and 50 mm irrigation over the control during both the cycle of Wheat-Maize rotation,respectively.These results demonstrated that,the gravel mulch technology could effectively promote the crop growth and gain better growth targets,ultimately affect the crop production.Overall,the gravel mulching technology provided an effective way to positively cope with sustainable agricultural production in dry land farm.(3)This study focuses on soil GHG emissions as affected by varying gravel mulching practices in a typical wheat-maize rotation system on the Loess Plateau of China.GHG emissions were significantly correlated with soil temperature and soil water-filled pore space(WFPS)throughout the experimental period.Compared to the control,gravel mulching has significantly decreased soil CO2 and CH4 emissions during the two cycles,but the patterns of soil N2 O emissions were inconsistent.This also led to the inconsistent results of the GWP.However,gravel mulching still played a positive role in reducing GHG intensity(GHGI)and carbon intensity(CI)(CF/Yield).The GHGI,relating to the GWP and crop production,significantly decreased by 35.1%,53.7% and 55.9% over cycle 1 and by 16.7%,19.6% and 37.2% over cycle 2 in WCK,GM and WGM compared to CK,respectively.The two-year average values of CF in WCK,GM and WGM treatments were 69.5%,45.5% and 11.2% % lower than that in CK.However,during cycle 1 the CI did not significantly affected,whereas during cycle 2 it affected,with a minimum value of-0.43±0.05 kg CO2-Ce kg-1 in WGM and-0.40±0.03 kg CO2-Ce kg-1 in GM,respectively.Although CI did not significantly affected by the application of gravel mulching during cycle 1,the impact of gravel mulching on CI tended to decrease with time.Therefore,further study should be conducted to investigate perennial influence of gravel mulching applications.These results indicates that gravel mulching has the potential to mitigate greenhouse gas emissions and enhance agroecosystem carbon balance for the wheat-maize cropping system in the Chinese Loess Plateau.(4)This study provided insight into crop yield and multilevel water use by evaluating crop productivity,ecological effects and water productivity as affected by gravel mulching in a typical wheat-maize rotation in a semi-arid region of Northwest China.Annual NPP and NEP,as affected by gravel mulching,increased,although there was a small change in NPP during cycle 1,but NPP during cycle 2 and NEP during both cycles significantly increased.Based on these results,multilevel water use efficiency,i.e.the ratio of productivity to water use at the vegetation,ecosystem,biomass and yield levels,was calculated in our study.No evidence of an effect on the annual WUEveg and WUEbio was observed under the two gravel mulching treatments,whereas in cycle 2,there was a significant effect,with a maximum value of 14.4 kg ha-1 mm-1 in WGM and 47.1±5.1 kg ha-1 mm-1 in GM,respectively.Compared to the control,the annual WUEeco increased by 40.6% and 49.2% under gravel mulching and by 39.1% and 53.8% under gravel mulching combined with irrigation,and the annual WUEyield increased by 57.6% and 51.4% under gravel mulching and by 39.8% and 37.7% under gravel mulching combined with irrigation during the two cycles,respectively.Our study also indicated that applying the gravel mulching during the first year has a great effect on crop yield,WUEeco and WUEyield,but elicits a slow increase during the subsequent year.Taking into account crop yield,ecological effects and water use,covering the soil with gravel is an effective approach to enhance multilevel water use efficiency while increasing the productivity of wheat-maize cropping system in semi-arid regions of China. |
PDF Full Text Request