Effects of drip and flood irrigation on carbon dioxide exchange and crop growth in the maize ecosystem in the Hetao Irrigation District,China

Drip irrigation and flood irrigation are major irrigation methods for maize crops in the Hetao Irrigation District,Inner Mongolia Autonomous Region,China.This research delves into the effects of these irrigation methods on carbon dioxide(CO_(2))exchange and crop growth in this region.The experimental site was divided into drip and flood irrigation zones.The irrigation schedules of this study aligned with the local commonly used irrigation schedule.We employed a developed chamber system to measure the diurnal CO_(2)exchange of maize plants during various growth stages under both drip and flood irrigation methods.From May to September in 2020 and 2021,two sets of repeated experiments were conducted.In each experiment,a total of nine measurements of CO_(2)exchange were performed to obtain carbon exchange data at different growth stages of maize crop.During each CO_(2)exchange measurement event,CO_(2)flux data were collected every two hours over a day-long period to capture the diurnal variations in CO_(2)exchange.During each CO_(2)exchange measurement event,the biological parameters(aboveground biomass and crop growth rate)of maize and environmental parameters(including air humidity,air temperature,precipitation,soil water content,and photosynthetically active radiation)were measured.The results indicated a V-shaped trend in net ecosystem CO_(2)exchange in daytime,reducing slowly at night,while the net assimilation rate(net primary productivity)exhibited a contrasting trend.Notably,compared with flood irrigation,drip irrigation demonstrated significantly higher average daily soil CO_(2)emission and greater average daily CO_(2)absorption by maize plants.Consequently,within the maize ecosystem,drip irrigation appeared more conducive to absorbing atmospheric CO_(2).Furthermore,drip irrigation demonstrated a faster crop growth rate and increased aboveground biomass compared with flood irrigation.A strong linear relationship existed between leaf area index and light utilization efficiency,irrespective of the irrigation method.Notably,drip irrigation displayed superior light use efficiency compared with flood irrigation.The final yield results corroborated these findings,indicating that drip irrigation yielded higher harvest index and overall yield than flood irrigation.The results of this study provide a basis for the selection of optimal irrigation methods commonly used in the Hetao Irrigation District.This research also serves as a reference for future irrigation studies that consider measurements of both carbon emissions and yield simultaneously.

Impacts of Sulfur and Microalgae Co-fertilization on Saline-alkaline Soil of Sunflower Field in Hetao Irrigation District

[Objectives]To evaluate the impacts of the elemental sulfur(S 0)and micro-algae(MA)co-fertilization on saline-alkaline soil of sunflower field in the Hetao Irrigation District(HID).[Methods]The greenhouse pot experiment was conducted with four treatments:control(CK),single S 0 fertilization(S),single MA fertilization(A),and S 0 and MA co-fertilization(SA)for comparing the selected soil properties and sunflower plant heights and weights in different treatments.[Results]The results showed that the mean soil organic matter(SOM)under the SA(25.08 g/kg)was significantly higher than that for the CK(20.59 g/kg),S(22.47 g/kg),and A(22.95 g/kg).The mean pH under the SA(7.75)was significantly lower than that for the CK(8.14),S(7.82),and A(7.96).The mean soil exchangeable Na+concentration under the SA was significantly lower than that for the S.The mean soil electrical conductivity(EC)under the SA was 9.76%lower than that for the S.The means of Cl-(1.22 g/kg)and SO 2-4(1.90 g/kg)in soil under the SA were lower than that for the S(1.30,2.06 g/kg)and A(1.31,1.97 g/kg),respectively.For plant height 3 at the late stage of plant growth,the mean plant height 3 under the SA(89.00 cm)was higher than that of the CK(69.60 cm)and A(74.33 cm).The total weights of the fresh sunflower heads,fresh stems,and dry seeds under the SA were higher than that for the CK,S,and A.[Conclusions]In conclusion,the S 0 and MA co-fertilization had positive effects on improving saline-alkaline soils,the soil under the S 0 and MA co-fertilization could be better conditions for promoting sunflower growth than that for the S,Z,and CK,and thereby the S 0 and MA co-fertilization could be a new idea to improve saline-alkaline soil in the cold and arid regions.

Applying a salinity response function and zoning saline land for three fi eld crops: a case study in the Hetao Irrigation District, Inner Mongolia, China

Salinity is one of the major abiotic factors affecting the growth and productivity of crops in Hetao Irrigation District, China. In this study, the salinity tolerances of three local crops, wheat （Triticum aestinum L.）, maize （Zea mays L.） and sunflower （Helianthus annuus L.）, growing in 76 farm fields are evaluated with modified discount function. Salinity ecological zones appropriate for these local crops are characterized and a case study is presented for crop salinity ecological zoning. The results show that the yield reductions of wheat, maize and sunflower when grown in saline soils are attributed primarily to a reduction in spikelet number, 1 000-grain weight and seed number per head, respectively. Sunflower is the most tolerant crop among the three which had a salinity tolerance index （ST-index） of 12.24, followed by spring maize and spring wheat with ST-Indices of 9.00 and 7.43, respectively. According to the crop salinity tolerance results, the arable land in the Heping Village of this district was subdivided into four salinity ecological zones： the most suitable, suitable, sub-suitable and unsuitable zones. The area proportion of the most suitable zone for wheat, maize and sunflower within the Heping Village was 27.5, 46.5 and 77.5%, respectively. Most of the most suitable zone occurred in the western part of the village. The results of this study provide the scientific basis for optimizing the local major crop distribution and improving cultural practices management in Hetao Irrigation District.

Characteristics and Development of Agricultural Soil in Hetao Irrigation District,Inner Mongolia

Hetao Irrigation District is located in the cold and arid region of Hetao Plain,Inner Mongolia,where the agricultural soil has unique characteristics.Although the agricultural soil properties in Hetao Irrigation Districts have been reported,the overall characteristics remain unclear.Through literature review and investigation,the overall characteristics,development patterns,and related reasons were explored,consequently providing theoretical support for enhancing soil utilization and formulating sustainable soil development strategies.The results showed that the agricultural soil in Hetao Irrigation District originated from the sedimentary layer and anthropogenic mellowing produced by the diversions of the Yellow River.The soil has periodic secondary salinization characteristics,accompanied by a slightly increasing pH value over time.It has low soil organic contents with a stable changing trend,low nitrogen,and phosphorus contents but high potassium and sulfur content,uneven nutrient distribution,diverse production performance,weak but stable ecological performance,and heterogeneous soil quality with a stable change trend.These findings indicate that this kind of soil can be used to plant diverse crops tolerant to different saline-alkali and requiring various nutrients.This agricultural soil is sustainable,but it is also faced with the problems of increased saline-alkali,nutrient loss,and pollution.

An Empirical Framework of Washing Salinity by Irrigation to Maintain Soil Quality in Hetao Irrigation District

[Objectives] To summarize the characteristics of washing salinity by irrigation in Hetao Irrigation District, and propose the empirical framework of washing salinity by irrigation to maintain soil quality, and provide a theoretical basis for maintaining the sustainable development of soil in Hetao Irrigation District. [Methods] The methods of experiment, questionnaire, on-the-spot investigation and literature review were used. [Results] This study proposed the empirical framework of washing salinity by irrigation to maintain soil quality in Hetao Irrigation District. Seven factors of the framework, including flood irrigation, land leveling, plastic film mulching, fertilization, soil organic matter, pH and salinity, and their relationships were determined. The characteristics of these factors in Hetao Irrigation District were investigated(flooding irrigation with a large amount of irrigation water, high amount of fertilizer application, low organic matter, high pH, large variation of salinity, etc.). The mechanisms and effects of various factors affecting soil quality in Hetao Irrigation District were analyzed(the mean soil organic matter(SOM) and pH were kept in the range of 10.9-13.9 g/kg and 8.0-8.15 in recent 35 years, respectively, and increased slightly, etc.). [Conclusions] The empirical framework can be used as a theoretical norm for evaluating soil quality under the condition of washing salinity by irrigation. Under the condition of washing salinity by irrigation, the agricultural soil quality in Hetao Irrigation District showed a stable trend over time. Using this framework, we can find soil problems, and adjust some unbalanced factors to maintain the stability of soil quality in Hetao Irrigation District, and can also provide a reference for other areas.

Reducing water and nitrogen inputs combined with plastic mulched ridge-furrow irrigation improves soil water and salt status in arid saline areas,China

Plastic mulched ridge-furrow irrigation is a useful method to improve crop productivity and decrease salt accumulation in arid saline areas.However,inappropriate irrigation and fertilizer practices may result in ecological and environmental problems.In order to improve the resource use efficiency in these areas,we investigated the effects of different irrigation amounts(400(I1),300(I2)and 200(I3)mm)and nitrogen application rates(300(F1)and 150(F2)kg N/hm^(2))on water consumption,salt variation and resource use efficiency of spring maize(Zea mays L.)in the Hetao Irrigation District(HID)of Northwest China in 2017 and 2018.Result showed that soil water contents were 0.2%-8.9%and 13.9%-18.1%lower for I2 and I3 than for I1,respectively,but that was slightly higher for F2 than for F1.Soil salt contents were 7.8%-23.5%and 48.5%-48.9%lower for I2 than for I1 and I3,but that was 1.6%-5.5%higher for F1 than for F2.Less salt leaching at the early growth stage(from sowing to six-leaf stage)and higher salt accumulation at the peak growth stage(from six-leaf to tasseling stage and from grain-filling to maturity stage)resulted in a higher soil salt content for I3 than for I1 and I2.Grain yields for I1 and I2 were significantly higher than that for I3 and irrigation water use efficiency for I2 was 14.7%-34.0%higher than that for I1.Compared with F1,F2 increased the partial factor productivity(PFP)of nitrogen fertilizer by more than 80%.PFP was not significantly different between I1F2 and I2F2,but significantly higher than those of other treatments.Considering the goal of saving water and nitrogen resources,and ensuring food security,we recommended the combination of I2F2 to ensure the sustainable development of agriculture in the HID and other similar arid saline areas.