| The dry farming plays an important role in food production,energy and economic development of China.The Loess Plateau is a typical dry farming area,however,due to unreasonable agricultural intensive activities since thousands of years,the area has been suffered from serious soil erosion and soil degradation,reduced soil water storage capacity,and serious loss of soil nutrients.In addition,seasonal droughts occur frequently in this region,leading to a decline in regional land productivity and a low and unstable crop yield.Improving soil water storage capacity and soil nutrient levels is a practical issue facing agricultural development in the region.Conservation tillage is considered as an effective measure to improve soil water storage capacity and nutrient levels,but single conservation tillage measures often show some disadvantages,such as soil compaction and high-level stratification of nutrients.Rotational tillage uses different farming methods in rotation,which can effectively overcome the disadvantages of a single farming method,so it can be conceived as an effective method to solve the drawbacks of a single farming measure.However,the practice of rotational tillage on the Loess Plateau is lacking,and the effects of soil moisture conservation,nutrient promotion,and yield of rotational tillage is still unknown.In view of this,a long-term in-situ tillage experiment(2008-2019)under the spring maize monoculture was conducted with a single factor random block design,to explore the effects of soil moisture conservation,nutrient promotion,and yield of rotational tillage.Nine rotational tillage including: continuous no-tillage treatment(NT),continuous subsoiling(ST),continuous plow tillage(PT),and two-year tillage rotation of no-tillage and subsoiling(NS),subsoiling and plow tillage rotation(SP),plow tillage and no-tillage rotation(PN),and three-year tillage rotation of no-tillage-no-tillage-subsoiling(NNS),no-tillage-plow tillage and subsoiling(NPS)and plow-plow-subsoiling(PPS).Soil water dynamics,soil structure,soil nutrients,soil bacterial characteristics and yield,economic profit were measured and analyzed.Our findings may provide a basis for the improvement of soil water conservation,soil nutrient and yield improvement of dry farmland in the region.The main findings are as follows:1)The implementation of rotational tillage significantly increased rainfall infiltration during the winter fallow period,increasing soil water supply during fallow period compared with PT,and then increased soil moisture and relieved spring drought.During 2008 to 2019,the average value of soil moisture replenishment during 11 fallow periods was: NPS> NT> SP> PN> ST> PT> NS> NNS> PPS.The NS had the highest soil moisture content at the end of fallow period,in the dry years,significantly increased soil moisture by 9.0% than PT(P<0.05).In the normal years,the PPS observed the highest soil moisture,5.2% higher than that of PT(P<0.05).In the wet years,soil moisture in NNS was the highest,and significantly increased by 5.2% compared with PT(P <0.05).Additionally,rainfall model and tillage had significant influence on soil water storage at growth stages.In dry years,NNS and NS significantly increased soil water storage by 14.5% and 13.9% at the tasseling stage compared to PT(P<0.05).NPS significantly increased soil water storage at filling stage by4.4% compared with PT(P<0.05).In normal years,the NNS and NPS significantly increased the soil water storage capacity by 7.3% and 4.9% compared to PT(P<0.05),whilst the NNS,NPS,NS,and ST significantly increased the soil water storage at filling stage than PT(P<0.05).0.05),by 8.1-11.9%.The increment can alleviate soil water stress caused by insufficient rainfall,ensure sufficient water supply and yield formation.In wet years,compared with PT,NT treatment significantly(P <0.05)increased soil water storage in the tasseling and filling stages by 6.5% and 4.6%,respectively.During the whole growth period,NNS,NPS,and PPS had the highest soil water storage at the depth of 0-200 cm in dry years,and NNS and NPS had the highest soil water storage in normal years,while NNS had the highest soil water storage in wet years.After 12 years of tillage management,the soil water consumption in each rotational tillage mainly occurred at 200-500 cm,and the highest soil water consumption was observed under ST treatment.2)With the extension of the tillage management,the soil bulk density,porosity,field water capacity,and soil water deficit showed the fluctuating trend.In the 0-60 cm soil depths,the average soil bulk density and porosity among the different rotational tillage differed weakly,although the soil porosity under the PPS,NS,SP,and PN rotational tillage were relatively higher,by1.4-2.4% higher than PT(P> 0.05).The water holding capacity of NPS,PPS,PN and ST treatments increased by 0.8-3.5% compared with PT(P> 0.05);the soil water deficit degree of NPS,PPS,PN and NT treatments significantly(P <0.05)increased by 6.6%,5.7%,7.8%,and 5.3%,compared with PT,respectively,while the SP significantly(P <0.05)decreased soil water deficit degree by 10.0% than PT did.Among the nine rotational tillage,the NNS observed the highest macro-aggregates distribution and the aggregates stability index than others,the increment were 2.7-11.5% and 3.8-21.1%,respectively.NT observed the highest water-stable macro-aggregates and lowest aggregates destruction rate.3)After years of tillage management,the soil organic carbon content and storage in each tillage increased compared with before the experiment,and the highest values were observed in ST,which significantly(P<0.05)increased by 6.2-21.7% and 12.8-21.3% compared with others.However,the soil total nitrogen content and storage observed the highest values under the PN rotational tillage,which significantly(P<0.05)increased by 3.4-19.6% and 2.6-14.9% compared with others.Soil total phosphorus and available phosphorus contents observed the highest values under the NPS rotational tillage;total potassium content observed the highest value under the NT treatment;soil available potassium contents observed the highest value under the SP rotational tillage.Rotational tillage significantly affected the soil bacterial community diversity,and the NPS had the highest bacterial diversity and richness index.The number of OUTs in the NPS increased by 1.0-9.1% compared to others,the Chao1 index increased by 4.9-27.8%,and the Shannon index increased by 0.6-3.1% than others.The redundancy analysis showed that that soil available phosphorus is the main driving factor that determine the composition of soil bacteria,followed by total nitrogen,total potassium and soil organic carbon,and total phosphorus has the least effect on the composition of soil bacteria.Moreover,oligotrophic species,such as Gemmatimonadete,negatively correlated with soil nutrient.Eutrophic species,such as Bacteroides,Firmicutes and Actinobacteria positively correlated with soil nutrient.Therefore,tillage with straw returning to the soil caused differential soil nutrient,which ultimately led to the generation of different species.4)The rainfall models had a significant influence on yield.ST treatment increased yields by 1.8-13.4% compared with others,in dry years.In normal years,the ST,NPS and NS observed the higher yields,and increased by 3.1-18.9%,2.5-18.3% and 2.5-18.3% than PPS,SP,PN,NT,and PT,respectively.In wet years,the NPS observed the highest yield,and increased by 2.4-15.2% in comparison to others.The NPS observed the highest average yield,economic profit,and precipitation utilization efficiency,nitrogen and phosphate partial productivity among nine rotational tillage.NPS increased yield and precipitation utilization efficiency by 2.3-15.3% compared to others,increased economic profit by 2.6-25.7%,increased nitrogen fertilizer partial productivity by 3.0-16.2%,and phosphate fertilizer partial productivity by 2.4-15.4%,compared with others.The water use efficiency observed highest value under ST treatment,increased by 0.4-11.4% in comparison to others.The 12-year in-situ experiment showed that the rotational tillage improved the soil structure of the arable layer,maintained a higher soil nutrient content,improved soil water storage and supply capacity,effectively promoted the absorption of water and nutrients,and increased yield,economic benefits,water and fertilizer use efficiency,and reduced the carbon footprint of agricultural production.Although the dominant rotational tillage varied with precipitation amount,the NPS rotation tillage observed the best effect.Therefore,the NPS is the most optimal among the nine tillage,so it could be recommended to apply in the agricultural production in the semi-arid and similar areas. |
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