Effects of combined drip irrigation and sub-surface pipe drainage on water and salt transport of saline-alkali soil in Xinjiang, China

Developing effective irrigation and drainage strategies to improve the quality of saline-alkali soil is vital for enhancing agricultural production and increasing economic returns. In this study, we explored how irrigation and drainage modes (flood irrigation, drip irrigation, and sub-surface pipe drainage under drip irrigation) improve the saline-alkali soil in Xinjiang, China. We aimed to study the transport characteristics of soil water and salt under different irrigation and drainage modes, and analyze the effects of the combination of irrigation and drainage on soil salt leaching, as well as its impacts on the growth of oil sunflower. Our results show that sub-surface pipe drainage under drip irrigation significantly reduced the soil salt content and soil water content at the 0–200 cm soil depth. Under sub-surface pipe drainage combined with drip irrigation, the mean soil salt content was reduced to below 10 g/kg after the second irrigation, and the soil salt content decreased as sub-surface pipe distance decreased. The mean soil salt content of flood irrigation exceeded 25 g/kg, and the mean soil desalination efficiency was 3.28%, which was lower than that of drip irrigation. The mean soil desalination rate under drip irrigation and sub-surface pipe drainage under drip irrigation was 19.30% and 58.12%, respectively. After sub-surface drainage regulation under drip irrigation, the germination percentage of oil sunflower seedlings was increased to more than 50%, which further confirmed that combined drip irrigation and sub-surface pipe drainage is very effective in improving the quality of saline-alkali soil and increasing the productivity of agricultural crops.

Effects of biodegradable mulch on soil water and heat conditions,yield and quality of processing tomatoes by drip irrigation

To combat the problem of residual film pollution and ensure the sustainable development of agriculture in oasis areas,a field experiment was carried out in 2019 at the Wuyi Farm Corps Irrigation Center Test Station in Urumqi,Northwest China.Four types of biodegradable mulches,traditional plastic mulchs and a control group(bare land;referred to as CK)were compared,including a total of six different treatments.Effects of mulching on soil water and heat conditions as well as the yield and quality of processing tomatoes under drip irrigation were examined.In addition,a comparative analysis of economic benefits of biodegradable mulches was performed.Principal component analysis and gray correlation analysis were used to evaluate suitable mulching varieties for planting processing tomatoes under drip irrigation.Our results show that,compared with CK,biodegradable mulches and traditional plastic mulch have a similar effect on retaining soil moisture at the seedling stage but significantly increase soil moisture by 0.5%-1.5%and 1.5%-3.0%in the middle and late growth periods(P<0.050),respectively.The difference in the thermal insulation effect between biodegradable mulch and plastic mulch gradually reduces as the crop grows.Compared with plastic mulch,the average soil temperature at 5-20 cm depth under biodegradable mulches is significantly lowered by 2.04°C-3.52°C and 0.52°C-0.88°C(P<0.050)at the seedling stage and the full growth period,respectively,and the water use efficiency,average fruit yield,and production-investment ratio under biodegradable mulches were reduced by 0.89%-6.63%,3.39%-8.69%,and 0.51%-6.33%(P<0.050),respectively.The comprehensive evaluation analysis suggests that the black oxidized biological double-degradation ecological mulch made from eco-benign plastic is the optimal film type under the study condition.Therefore,from the perspective of sustainable development,biodegradable mulch is a competitive alternative to plastic mulch for large-scale tomato production under drip irrigation in the oasis.

Effects of timing and duration under brackish water mulch drip irrigation on cotton yield in northern Xinjiang,China

The brackish water is an important potential water source and has frequently been utilized to drip-irrigate cotton due to the water shortage in the arid region of Xinjiang,northwestern of China.The brackish water is usually saline water with salinity ranging from 1 g/L to 5 g/L,which is widely distributed in this area,so the reasonable use of that brackish water may not only play a vital role in the local agricultural production,but also save plenty of freshwater.However,irrigation with brackish water usually causes the reduction of crop yield and soil salinization which can negatively impact plants through three major components:osmotic,nutritious and toxic stresses.Therefore,a field experiment,with eight different time-series irrigation modes using brackish water(3.5±0.2)g/L and freshwater(<1 g/L),beneath a combined film and drip-irrigation system was carried out to study the changes of soil salt content and cotton yield aiming to search for a balanced method during the 2 cotton growing seasons in 2012 and 2013.The results indicated that the time-series irrigation modes determined the soil salinity and moisture distribution based on observed spatio-temporal distribution of water content and electric conductivity,and soil salinity generally gathered at the depth of 0-10 cm and 60 cm of soil with the increase of irrigation quota.Moreover,the results demonstrated that the yields of cotton which was grown using brackish water and freshwater were better than those only using freshwater and the soil salinity with reasonable irrigation timing was not accumulated obviously.

2001-2020年中国地表温度时空分异及归因分析

The variation of land surface temperature(LST)has a vital impact on the energy balance of the land surface process and the ecosystem stability.Based on MDO11C3,we mainly used regression analysis,GIS spatial analysis,correlation analysis,and center-of-gravity model,to analyze the LST variation and its spatiotemporal differentiation in China from 2001 to 2020.Furthermore,we employed the Geodetector to identify the dominant factors contributing to LST variation in 38 eco-geographic zones of China and investigate the underlying causes of its pattern.The results indicate the following:(1)From 2001 to 2020,the LST climate average in China is 9.6℃,with a general pattern of higher temperatures in the southeast and northwest regions,lower temperatures in the northeast and Qinghai-Tibet Plateau,and higher temperatures in plains compared to lower temperatures in mountainous areas.Generally,LST has a significant negative correlation with elevation,with a correlation coefficient of–0.66.China’s First Ladder has the most pronounced negative correlation,with a correlation coefficient of–0.76 and the lapse rate of LST is 0.57℃/100 m.(2)The change rate of LST in China during the study is 0.21℃/10 a,and the warming area accounts for 78%,demonstrating the overall spatial pattern a“multi-core warming and axial cooling”.(3)LST’s variation exhibits prominent seasonal characteristics in the whole country.The spatial distribution of average value in winter and summer differs significantly from other seasons and shows more noticeable fluctuations.The centroid trajectory of the seasonal warming/cooling area is close to a loop shape and displays corresponding seasonal reverse movement.Cooling areas exhibit more substantial centroid movement,indicating greater regional variation and seasonal variability.(4)China’s LST variation is driven by both natural influences and human activities,of which natural factors contribute more,with sunshine duration and altitude being key factors.The boundary trend between the two dominant type areas is highly consistent with the“Heihe-Tengchong Line”.The eastern region is mostly dominated by human activity in conjunction with terrain factors,while the western region is predominantly influenced by natural factors,which enhance/weaken the change range of LST through mutual coupling with climate,terrain,vegetation,and other factors.This study offers valuable scientific references for addressing climate change,analyzing surface environmental patterns,and protecting the ecological environment.

Comparative investigation on soil salinity leaching under subsurface drainage and ditch drainage in Xinjiang arid region

This study was carried out to explore the effects of leaching salinity under subsurface drainage and mulched drip irrigation on saline and alkaline land from the year 2012 to 2014 in Xinjiang Region of China.Three sampled points were both set up in the subsurface drainage and ditch drainage areas.Soil samples were obtained at varied depths.Through observing the underground water table under each sampled point and measuring the electrical conductivity(EC)of the soil extracts,the following results were obtained:(1)after draining,the underground water table ranged from 1.6 m to 2.2 m in the ditch drainage area,and ranged from 1.5 m to 2.2 m in the subsurface drainage area.Thus,both irrigations could control underground water table below 1.5 m which is deeper than the main water-absorbing layers of crop root systems;(2)for subsurface drainage,the closer to the pipe,the better to leach salinity;decreased from the initial 13.54-22.95 g/kg to 8.20-11.47 g/kg;(3)compared with the amounts in 2012,soil total salt at each sampling point at depths of 0-200 cm in subsurface drainage area decreased by 42.99%,36.84%and 24.41%respectively in 2014;and in ditch drainage area decreased by 46.85%,38.12%and 30.80%respectively in 2014.The results showed both ditch and subsurface drainage could leach salinity effectively.

Effects of water-fertilizer coupling on root distribution and yield of Chinese Jujube trees in Xinjiang

Water and fertilizer are the two main factors which promote the rapid growth of Jujube(Ziziphus jujuba)trees.Studies of root systems and the nutrition-use efficiency of dense,dwarfed fruit trees are limited,especially in an extremely arid region with drip irrigation.The experiment was conducted in a 12-year-old dwarf jujube planting basement in Hami from 2013 to 2015.In this experiment,root length density and root weight density were calculated and found to range from 75 cm to 275 cm in horizontal distance,and from 0 to 90 cm in vertical depth,treated with three drip irrigation quota gradients and three fertilizer rates with each treatment replicated three times.The results showed that,as the amount of nitrogen applied increased gradually,the jujubes’growth amount increased,reaching a maximum when an optimal concentration was applied.However,the jujubes’growth was inhibited,and the growth declined when the amount of nitrogen applied was more than the optimal concentration.At an appropriate level of nitrogen,the growth,yield and quality of jujube trees could be guaranteed.If the rate of nitrogen application was lowered,the jujubes’growth would inhibit,and hence the yield wound be seriously impacted.The optimal irrigation quota and fertilization amount were found to be 900 mm and 1500-1800 kg/hm^(2),respectively.The research findings were of significance and hold great promise for the development of the forestry and fruit industries in the arid region of Xinjiang.At the same time,there was a further study on irrigation technique,focusing on the combined effect of the dwarfed-planting technique and drip irrigation on jujube trees;with this information,the application efficiency of water and fertilizer can be optimized,leading to higher profits and economic efficiency.

Effects of biodegradable mulching films on soil hydrothermal conditions and yield of drip-irrigated cotton(Gossypium hirsutum L.)

The pollution of cotton fields by residual films is serious on ground that has been subjected to long-term drip irrigation in Xinjiang,China,and biodegradable mulches are therefore advocated as an alternative to plastic ones.In this study the mulching with biodegradable films under drip irrigation conditions in the extremely arid region of Xinjiang was investigated to determine the effects on soil hydrothermal conditions and cotton(Gossypium hirsutum L.)yield over two consecutive years(2019-2020)using plastic mulch made from polyethylene(PE)film and four types of biodegradable films,including black opaque oxidation-biodegradable film(M1),colorless transparent oxidation-biodegradable film(M2),black opaque fully biodegradable film(M3)and white translucent fully biodegradable film(M4),which had different levels of biodegradability(i.e.different degradation times and rates).The biodegradability,soil water contents,soil temperatures and cotton yields were compared between the degradable(M1 to M4)and PE films.The results indicated that M2 was degraded the quickest and showed the highest degree of degradation compared with the other degradable films and PE films.The degradation rates of the various mulching films were ranked in a descending order as M2,M4,M1,M3 and PE,but the PE mulch exhibited the best performance in terms of soil water and heat conservation throughout the growth period.The soil heat preservation and moisture conservation performance under biodegradable films mulching at the cotton seedling stage and budding stage was similar to that of PE film.The average soil temperature at a depth of 5 cm under mulching with the degradable films was 2.66°C-5.06°C(p<0.05)lower than that under traditional PE films at the flowering stage.At the late stage of cotton growth,the water content of shallow soil mulched with PE film was better for plant grown than that under the biodegradable films.The effect of film degradation on the shallow soil water content was much greater than that in deep soil,especially at a depth of 0-40 cm.However,in all treatments,the seedling rate and growth index of cotton under M2 were equivalent to that found under the PE film.Moreover,the cotton yield using M2 was slightly higher than that for the PE film.Compared with the PE film,the yield of cotton mulched with M1,M3 and M4 was decreased by 7.50%,6.45%and 2.83%in 2019,and 9.82%,6.48%,and 2.13%,in 2020,respectively.Therefore,based on the performance in improving cotton yield and maintaining soil moisture,the biodegradable transparent film(M2)with an 80 d induction period is recommended as a competitive alternative to plastic mulch to enhance crop yield and control soil pollution.

Effects of nitrogen fertilizer application on saline-alkali land cotton in China quantified using meta-analysis and regression analysis

Nitrogen fertilizer application is an important means to promote cotton production in saline-alkali land.A metaanalysis and regression analysis of 49 peer-reviewed studies were conducted using yield data(373 data points),dry matter accumulation(114 data points),and water use efficiency(157 data points)to quantify the effect of nitrogen fertilizer on the yield,dry matter accumulation,and water use efficiency of cotton in saline-alkali land in China for different planting management practices and different growing environments.The results showed that the nitrogen application significantly improved the yield,dry matter accumulation,and water use efficiency by 34.11%,36.27%,and 33.87%,respectively,compared with no nitrogen application.The largest improvements in the yield,dry matter accumulation,and water use efficiency occurred in areas where saline-alkali land had been improved for many years,in Eastern China,South Central China,and Northwest China(areas with annual average precipitation≤200 mm or>800 mm,and annual average evaporation≤800 mm or>2400 mm),in areas with trickle irrigation,and fields with a planting density of 100000 to 250000 plants/hm2.Cotton exhibited the optimal response to nitrogen application at a rate of 300-375 kg/hm2,a basal application ratio of 20%-40%,and top-dressing in the cotton bud,flowering boll,and full boll stages.The effect of nitrogen application increased as the salinity increased.A suitable nitrogen application rate,top-dressing ratio,and top-dressing period are crucial for increasing cotton production in saline-alkali land,although environmental differences and planting measures have to be considered.This study provided information on the correct application of nitrogen fertilizer to maximize its benefits and suggests controlling nitrogen fertilizer inputs in agriculture to protect the soil environment and ensure sustainable agricultural development.

Land use change characteristics affected by water saving practices in Manas River Basin,China using Landsat satellite images

The characteristics and influencing factors of land use change under arid conditions were studied in the Manas River Basin in Xinjiang Region,Northwest China.Landsat satellite images acquired in 1976,1990,2000,2010 and 2015 over the study area were used as basic data.Land use change,the rate of change of land use,land use transfer and other aspects revealed the characteristics of land use change and related factors as influenced by water conditions in the basin.The results showed that:(1)Over nearly 50 years,land reclamation in the Manas River Basin resulted in the rapid expansion of an artificial oasis area,and promoted the process of‘oasis urbanization’,and accelerated the development of the river basin economy.(2)In 2000,the popularization of drip irrigation under mulch technology led to the rapid growth of cultivated land and development land in the watershed.Meanwhile,the water table declined in the desert area of the lower reaches of the river basin,and the area occupied by sparse shrub forest and grassland decreased.(3)Before popularization of water-saving technology,woodland,grassland and development land transformed to cultivated land in the amounts of 93.46 km^(2),2542.93 km^(2) and 137.53 km^(2),respectively,and woodland transformed in the amount of 189.64 km^(2).After water-saving technology was popularized,woodland,grassland and development land were transformed into cultivated land in the amounts of 567.41 km^(2),1756.2 km^(2) and 37.36 km^(2),respectively.(4)The popularization of water-saving technology made the dynamic degree of cultivated land and development land more active,and further increased landscape fragmentation and landscape heterogeneity.The level of urbanization development,the level of economic development and the dry humidity of the basin became the main factors affecting the change of land use in the basin.

Variations of soil quality from continuously planting greenhouses in North China

Vegetable greenhouses form a significant land utilisation pattern in China.A case study of the greenhouse soil quality changes and potential risk to humans under a specific long-term environment,which includes high fertilization rates,high temperatures and humidity levels and out-of-season cultivation,is presented in this study.Soil profiles of 72 representative solar greenhouses with various planting years were sampled in Shouguang City,which is the birthplace of winter greenhouse in China.The temporal distribution of soil quality changes were quantitatively evaluated through the application of a correlation analysis and soil quality assessment.The soil was highly enriched with phosphorus and potassium and had low organic matter content.The organic matter,nitrogen,phosphorus and potassium contents increased with the years planted,reached their peak values after 5-10 a,and declined as the soil layer’s depth increased.The infiltration rate of nitrate was relatively high,which poses risks to underground water safety.A comprehensive soil quality assessment revealed that in vegetable greenhouses planted for different periods,the soil quality improved at first and then sharply declined after 10 a.Studying greenhouse soil quality changes will aid in implementing nutrient management strategies to improve the soil quality and sustainable development programs for the vegetable industry.

Effects of autumn plowing on the movement and correlation of moisture,heat and nitrate nitrogen in seasonal freeze-thaw soil

A two-year experiment was established in northern Xinjiang to investigate the effects of autumn plowing methods on nitrate nitrogen accumulation,spring-sown soil conditions and cotton emergence rate,and to explore the response relationship between soil water,heat and nitrate nitrogen.The experiment included five autumn plowing treatments,namely,plough tillage(FG),no-tillage(MG),ridge and furrow alternation(LG),plough tillage with straw mulch(FJ)and plough tillage with activated charcoal mulch(FH).The results showed that both FH and FJ treatments were beneficial to promote the nitrate-nitrogen accumulation in topsoil,while FG,MG and LG treatments aggravated the nitrate nitrogen leaching in topsoil.During the freezing period,FH and FJ treatments were beneficial to reduce soil heat loss and facilitate the coordinated upward migration of soil water and nitrate nitrogen.In the thawing period,FH and FJ treatments favored suppressing the synergistic downward transport of soil water and nitrate-nitrogen and motivated the synergistic upward migration of heat and nitrate nitrogen in deep soil.Binary regression analysis suggested that the interaction between water,heat and nitrate nitrogen under FH and FJ treatments showed a highly significant correlation.FH and FJ treatments showed obvious advantages in regulating soil conditions and optimizing soil water,heat and nitrate nitrogen co-transport mechanism.During the spring sowing period,the FH and FJ treatments increased the average soil temperature by 0.99℃and 1.29℃,and the average soil moisture content by 6.01%and 8.70%,and the average soil nitrate content by 10.20 mg/kg and 10.47 mg/kg,in the 0-25 cm soil layer,respectively.FH and FJ treatments significantly grew the emergence rate of cotton,which can be used as the main autumn tillage strategies in arid areas of northern Xinjiang.