Ridge-furrow plastic mulching with a suitable planting density enhances rainwater productivity,grain yield and economic benefit of rainfed maize

Soil surface mulching and planting density regulation are widely used for effective utilization of limited rainwater resources and improvement of crop productivity in dryland farming.However,the combined effects of mulching type and planting density on maize growth and yield have been seldom studied,especially in different hydrological years.A field experiment was conducted to evaluate the effects of mulching type and planting density on the soil temperature,growth,grain yield(GY),water use efficiency(WUE)and economic benefit of rainfed maize in the drylands of northern China during 2015-2017.Precipitation fluctuated over the three years.There were four mulching types(NM,flat cultivation with non-mulching;SM,flat cultivation with straw mulching;RP,plastic-mulched ridge plus bare furrow;RPFS,plastic-mulched ridge plus straw-mulched furrow)and three planting densities(LD,low planting density,45.0×10^3 plants/hm^2;MD,medium planting density,67.5×10^3 plants/hm^2;HD,high planting density,90.0×10^3 plants/hm^2).Results showed that soil temperature was higher with RP and lower with SM compared with NM,but no significant difference was found between RPFS and NM.More soil water was retained by soil mulching at the early growth stage,but it significantly varied at the middle and late growth stages.Maize growth was significantly improved by soil mulching.With increasing planting density,stem diameter,net photosynthetic rate and chlorophyll content tended to decline,whereas a single-peak trend in biomass yield was observed.Mulching type and planting density did not have significant effect on evapotranspiration(ET),but GY and WUE were significantly affected.There were significant interacting effects of mulching type and planting density on biomass yield,GY,ET and WUE.Compared with NM,RPFS,RP and SM increased GY by 57.5%,50.8%and 18.9%,and increased WUE by 66.6%,54.3%and 18.1%,respectively.At MD,GY increased by 41.4%and 25.2%,and WUE increased by 38.6%and 22.4%compared with those of at LD and HD.The highest maize GY(7023.2 kg/hm^2)was observed under MD+RPFS,but the value(6699.1 kg/hm^2)was insignificant under MD+RP.Similar trends were observed for WUE under MD+RP and MD+RPFS,but no significant difference was observed between these two combinations.In terms of economic benefit,net income under MD+RP was the highest with a 9.8%increase compared with that of under MD+RPFS.Therefore,we concluded that RP cultivation pattern with a suitable planting density(67.5×10^3 plants/hm^2)is promising for rainwater resources utilization and maize production in the drylands of northern China.

Effect of biochar aging in agricultural soil on its wetting properties and surface structure

Biochar wettability and ability to accumulate moisture inside the porous space are crucial for improving soil fertility,regulating soil water balance,and regulating nutrients.However,a long-term interaction of biochar with agricultural soils may drastically alter the wetting properties and,eventually,influence water holding capacity and the structure of soils.In this work,the structure and wetting properties of biochar samples after 6-year long exposure to a sandy loam Spodosol with a crop rotation and mineral fertilizers application were studied.It was found that the elemental composition of the aged biochars was richer and more"soil-like",which is explained by the presence of the mineral crust on the biochar surface.The temporal evolution of biochar in the soil without any mineral fertilizer application resulted in significant improvement of its surface wettability due to the effects of various environmental factors.The lateral surface of biochar after 6-year interaction with the soil changes into a loose porous layer in a form of grooved base filled with adherent mineral soil and clay particles.Contrary,the application of the mineral fertilizer to the soil resulted in decreased wettability of the biochar lateral surfaces due to a decrease in the polar component of surface energy and the crusting of the surface with fine material,which blocks the pore space of the biochar.As a result,water capacity of the biochar from the treatment with the fertilizer decreased compared to the biochar samples collected from the soil without the fertilizer application.The radial biochar surfaces of both types of samples collected from the soil were open vessels filled with soil particles that slow down complete wetting and water absorption.The treatment of the biochar samples with surfactants drastically increased wettability of lateral surface and water absorption capacity of control samples as compared to the samples collected from the soil.The obtained results support the idea that the hydrophilisation of biochar caused by the adhesion of soil particles and treatment of its pore surface with surfactants,can improve the water-holding capacity of the sandy loam Spodosol in the plant-available range of soil water.

New approaches for evaluation of soil health, sensitivity and resistance to degradation

Assessment of soil health requires complexevaluation of properties and functions responsible for abroad range of ecosystem services. Numerous soil qualityindices (SQI) have been suggested for the evaluation ofspecific groups of soil functions, but comparison of variousSQI is impossible because they are based on a combinationof specific soil properties. To avoid this problem, wesuggest an SQI-area approach based on the comparison ofthe areas on a radar diagram of a combination of chemical,biological and physical properties. The new approach isindependent of the SQI principle and allows rapid andsimple comparison of parameter groups and soils. Anotherapproach analyzing the resistance and sensitivity ofproperties to degradation is suggested for a detailedevaluation of soil health. The resistance and sensitivityof soil properties are determined through comparison withthe decrease of soil organic carbon (SOC) as a universalparameter responsible for many functions. The SQI-areaand resistance/sensitivity approaches were tested based on quences after the ab and on ment of agricultural soils. Both the SQI-area and the resistance/sensitivity approaches areuseful for basic and applied research, and for decisionmakersto evaluate land-use practices and measure thedegree of soil degradation.

Net ecosystem carbon exchange for Bermuda grass growing in mesocosms as affected by irrigation frequency

Intensification of grazed grasslands following conversion from dryland to irrigated farming has the potential to alter ecosystem carbon(C)cycling and affect components of carbon dioxide(CO_(2))exchange that could lead to either net accumulation or loss of soil C.While there are many studies on the effect of water availability on biomass production and soil C stocks,much less is known about the effect of the frequency of water inputs on the components of CO_(2)exchange.We grew Bermuda grass(Cynodon dactylon L.)in mesocosms under irrigation frequencies of every day(I_(1) treatment,30 d),every two days(I_(2) treatment,12 d),every three days(I_(3) treatment,30 d),and every six days(I_(6) treatment,18 d,after I_(2) treatment).Rates of CO_(2)exchange for estimating net ecosystem CO_(2)exchange(F_(N)),ecosystem respiration(R_(E)),and soil respiration(R_(S))were measured,and gross C uptake by plants(F_(G))and respiration from leaves(R_(L))were calculated during two periods,1–12 and 13–30 d,of the 30-d experiment.During the first 12 d,there were no significant differences in cumulative F_(N)(mean±standard deviation,61±30 g C m^(-2),n=4).During the subsequent 18 d,cumulative F_(N) decreased with decreasing irrigation frequency and increasing cumulative soil water deficit(W),with values of 70±22,60±16,and 18±12 g C m^(-2) for the I_(1),I_(3),and I_(6) treatments,respectively.There were similar decreases in F_(G),R_(E),and R_(L) with increasing W,but differences in R_(S) were not significant.Use of the C_(4) grass growing in a C_(3)-derived soil enabled partitioning of R_(S) into its autotrophic(R_(A))and heterotrophic(R_(H))components using a^(13)C natural abundance isotopic technique at the end of the experiment when differences in cumulative W between the treatments were the greatest.The values of R_(H) and its percentage contributions to R_(S)(43%±8%,42%±8%,and 8%±5%for the I_(1),I_(3),and I_(6) treatments,respectively)suggested that R_(H) remained unaffected across a wide range of W and then decreased under extreme W.There were no significant differences in aboveground biomass between the treatments.Nitrous oxide(N_(2)O)emission was measured to determine if there was a trade-off effect between irrigation frequency and increasing W on net greenhouse gas emission,but no significant differences were found between the treatments.These findings suggest that over short periods in well-drained soil,irrigation frequency could be managed to manipulate soil water deficit in order to reduce net belowground respiratory C losses,particularly those from the microbial decomposition of soil organic matter,with no significant effect on biomass production and N_(2)O emission.

Predicting erosion and sediment yield in a mesoscale basin in the semiarid monsoon region Miyun/China

Introduction:Changes in land use and agricultural management have caused a strong increase in sediment and particulate phosphorus input into the Miyun reservoir.The simulation of the relevant runoff and sediment fluxes at the mesoscale needs adequate procedures,adapted to a semiarid monsoon climate and regional land-use pattern.Results:The modified Universal Soil Loss Equation(USLE-M)was integrated into the STOFFBILANZ model to calculate daily soil losses in the entire Miyun catchment area.The results are well within the range of monitoring data from Wischmeier plots that are located inside the investigation area.For the reference year 2009,soil erosion was estimated at an average of 952 kg ha^(-1) year^(-1).Daily based simulation of sediment input into surface waters was done in the next step,taking into account the likeliness of sediment input and sediment delivery ratio.Average sediment inputs are by 113 kg ha^(-1) year^(-1).Critical source areas are located on cropland and are particularly relevant on the former lakebed of the Miyun reservoir which has recently been used for corn cropping.Conclusions:Compared with observation data from the Bai and Chao rivers,the simulation of sediment loads showed a satisfying agreement that underlines the suitability of the selected approach to substitute recently used one-year balances based on the Universal Soil Loss Equation(USLE)approach.Conservation tillage was selected as a possible mitigation option to reduce soil erosion and sediment loads.Owing to the limited availability of spatial and monitoring data,the simulations are approximate and only a first step in contributing to an integrated river basin management that should be improved in future.