Increase In Irrigation Amount Research Articles

Compound effects of biochar application and irrigation on soil water and temperature transport

The issue of soil salinization poses a significant barrier to sustainable agricultural development, particularly in arid and semi-arid regions. Finding methods to enhance the quality of salinized soils while conserving water resources has become a pressing challenge. In arid and semi-arid environments, conserving water resources while maintaining soil health is a critical challenge. This study, conducted from 2021 to 2023, aimed to explore the combined effects of irrigation and biochar application on soil physicochemical properties, such as bulk density, porosity, and pH, as well as on Weighted Plane Soil Water Storage (WPSWS), soil temperature, and soil water evaporation. The experimental design included four irrigation levels, based on actual crop evapotranspiration (ETc): I1 (0.6 ETc), I2 (0.8 ETc), I3 (1.0 ETc), and I4 (1.2 ETc), coupled with four amounts of biochar application (AOBA) of 0, 10, 20, and 30 t ha−1, designated as C0, C10, C20, and C30, respectively. Through binary quadratic regression analysis, we sought to identify the optimal combination of irrigation amount and AOBA for enhancing soil quality. The results revealed that as AOBA increased from 10 to 30 t ha−1, soil bulk density decreased by 1.31–8.58% and soil pH by 0.23–1.31%. However, higher levels of AOBA adversely affected WPSWS, with the C10 treatment showing the maximum improvement in WPSWS, registering an average increase of 6.77, 7.49, and 11.16% compared to the C0, C20, and C30 treatments, respectively. We observed that an increase in irrigation amount significantly elevated accumulated soil evaporation (ASE) and WPSWS but led to a reduction in accumulated soil temperature (AST). The most notable soil quality improvements were recorded when irrigation levels were between 340 and 380 mm and AOBA ranged from 10 to 25 t ha−1. This study provides insights into the effective combination of biochar application and irrigation for optimizing soil resilience, thereby offering a sustainable approach to soil management in water-limited environments.

Soybean Yield Simulation and Sustainability Assessment Based on the DSSAT-CROPGRO-Soybean Model.

In order to ensure national grain and oil security, it is imperative to expand the soybean planting area in the Xinjiang region. However, the scarcity of water resources in southern Xinjiang, the relatively backward soybean planting technology, and the lack of a supporting irrigation system have negatively impacted soybean planting and yield. In 2022 and 2023, we conducted an experiment which included three irrigation amounts of 27 mm, 36 mm, and 45 mm and analyzed the changes in dry mass and yield. Additionally, we simulated the potential yield using the corrected DSSAT-CROPGRO-Soybean model and biomass based on the meteorological data from 1994 to 2023. The results demonstrated that the model was capable of accurately predicting soybean emergence (the relative root mean square error (nRMSE) = 0, the absolute relative error (ARE) = 0), flowering (nRMSE = 0, ARE = 2.78%), maturity (nRMSE = 0, ARE = 3.21%). The model demonstrated high levels of accuracy in predicting soybean biomass (R2 = 0.98, nRMSE = 20.50%, ARE = 20.63%), 0-80 cm soil water storage (R2 = 0.64, nRMSE = 7.78%, ARE = 3.24%), and yield (R2 = 0.81, nRMSE = 10.83%, ARE = 8.79%). The biomass of soybean plants increases with the increase in irrigation amount. The highest biomass of 63 mm is 9379.19 kg·hm-2. When the irrigation yield is 36-45 mm (p < 0.05), the maximum yield can reach 4984.73 kg·hm-2; the maximum efficiency of soybean irrigation water was 33-36 mm. In light of the impact of soybean yield and irrigation water use efficiency, the optimal irrigation amount for soybean cultivation in southern Xinjiang is estimated to be between 36 and 42 mm. The simulation results provide a theoretical foundation for soybean cultivation in southern Xinjiang.

Effects of irrigation and nitrogen topdressing on water and nitrogen use efficiency for winter wheat with micro-sprinkling hose irrigation in North China

In order to explore the efficient use of water and nitrogen for winter wheat under irrigation with micro-sprinkling hose, two-season field experiments were conducted to evaluate the effects of irrigation levels and nitrogen application rate on yield, water productivity (WP) and nitrogen partial factor productivity (NPFP). Three irrigation levels were 60 %, 65 %, and 70 % field capacity (FC) during the reviving to jointing stage, 65 %, 70 %, and 75 % FC after the jointing stage, referred to as W1, W2 and W3, respectively. The irrigating water quota is 30 mm. The five N topdressing period treatments were reviving period + booting stage (N1), jointing + booting stage (N2), reviving period (N3), jointing stage (N4), and booting stage (N5). The results showed that the water consumption, leaf area index, plant height, biomass, grain yield, and NPFP increased with an increase in irrigation amount, and the WP decreased with an increase in irrigation amount. Nitrogen applied during the reviving period was beneficial for increasing grain yield, WP, and NPFP under the irrigation level W1; nitrogen applied during the jointing period was beneficial for increasing grain yield, WP, and NPFP for winter wheat under the W2 and W3 irrigation levels. The W3N2 treatment resulted in the highest grain yield (8.98 t·ha−1), but it was not significant difference from W2N2 (average of 8.92 t·ha−1). After a comprehensive evaluation based on grain yield, WP and NPFP, the appropriate modes of irrigation and nitrogen is the treatment of W2N2 (65 % and 70 % FC irrigation treatments during the reviving to jointing stage and the stages after jointing stage, respectively; the nitrogen topdressing during jointing + booting stage) for winter wheat using micro-sprinkling hose irrigation in North China.

Effects of increasing drip irrigation at different maize growth stages on soil microorganisms.

To investigate the effects of different drip irrigation periods on soil microbial communities and functions. Increasing drip irrigation amount at the seedling (S), jointing (J), bell (B), tasseling (T) and grain filling (G) stages of maize were studied using no increase in irrigation amount as control (CK). Principal component analysis was conducted to comprehensively evaluate soil microbial quality following the different drip irrigation treatments. In addition, the characteristics of the community structure and the potential functional composition of soil bacteria and fungi were comparatively analyzed by combining amplicon sequencing and functional prediction methods. The results indicated that MBNT15 was the most important genus for the classification of soil bacterial samples, Saitozyma was the most important genus for the classification of soil fungal samples, and fungi were more important than bacteria for the classification of soil microbial samples. Compared with fungal communities, bacterial communities exhibited high levels of functional diversity. The proportion of metabolism was the highest in the prediction of bacterial primary functions, and carbohydrate metabolism and amino acid metabolism were important functions in the prediction of bacterial secondary functions. BugBase phenotype prediction results showed that soil bacteria under B treatment had a higher number of aerobic bacteria and greater resistance to disease and stress. The J treatment had the highest number of bacteria with biofilm forms, and the J, S, and G treatments contained more potentially pathogenic bacteria but fewer stress-tolerant bacteria compared with the CK treatment. The number of Saprotroph was the largest and the number of Symbiotroph was the least. The relative abundances of Saprotroph, Pathotroph and Symbiotroph were 68.60%~74.33%, 15.76%~20.60% and 9.16%~11.13%, respectively. The findings provide a reference for conserving water resources, improving maize yield, and predicting soil microbial metabolic potential and function by reflecting the richness of the soil microbial community structure in maize fields.

Impacts of irrigation with treated livestock wastewater on the accumulation characteristic of ARGs in the farmland soil: a case study in Hohhot, China.

Irrigation with treated livestock wastewater (TWW) is a promising strategy for reusing resources. However, TWW irrigation might introduce antibiotic resistant genes (ARGs) into the soil, posing environmental risks associated with antibiotic resistance. This study focuses on investigating the influence of irrigation amounts and duration on the fate of ARGs and identifies key factors driving their changes. The results showed that there were 13 ARGs in TWW, while only 5 ARGs were detected in irrigated soil. That is some introduced ARGs from TWW could not persistently exist in the soil. After 1-year irrigation, an increase in irrigation amount from 0.016t/m2 to 0.048t/m2 significantly enhanced the abundance of tetC by 29.81%, while ermB and sul2 decreased by 45.37% and 76.47%, respectively (p < 0.01). After 2-year irrigation, the abundance of tetC, ermB, ermF, dfrA1, and total ARGs significantly increased (p < 0.05) when the irrigation amount increased. The abundances of ARGs after 2-year irrigation were found to be 2.5-34.4 times higher than 1 year. Obviously, the irrigation years intensified the positive correlation between ARGs abundance and irrigation amount. TetC and ermF were the dominant genes resulting in the accumulation of ARGs. TWW irrigation increased the content of organic matter and total nitrogen in the soil, which affected microbial community structure. The changes of the potential host were the determining factors driving the ARGs abundance. Our study demonstrated that continuous TWW irrigation for 2 years led to a substantial accumulation of ARGs in soil.

Water management, planting slope indicators, and economic benefit analysis for Panax notoginseng production decision under shaded and rain-shelter cultivation: A three-year sloping fields experiment

Panax notoginseng cultivation planting conditions are harsh and require high soil moisture and slope of cultivated land, plus it takes 3–7 years from planting to harvesting. At present, the continuous crop barrier of Panax notoginseng has not been solved, which makes the arable land suitable for planting significantly reduced. And yet, there is almost no report on the impact of coupling water and slope on the growth of Panax notoginseng. Therefore, this study aims to explore the effects of different irrigation levels and slopes on soil water content (SWC) in the root zone, soil nutrient content, root characteristics, yield, water use efficiency (WUE), partial fertilizer productivity (PFP) and economic benefits of Panax notoginseng. During 2018–2020, a field experiment was conducted in the Panax notoginseng growing seasons with three irrigation levels (I1: 70–75% θFC, I2: 75–80% θFC, I3: 80–85% θFC) and three slopes (S1: 2.43°, S2: 6.38°, S3: 16.38°). The results evidenced that soil water and nutrient content increased with increasing irrigation and decreased with increasing slope. The yield of Panax notoginseng, root morphological characteristics, WUE, PFP, and economic benefits showed a trend of increasing first and then decreasing with the increase of irrigation amount and slope, which increased with the increase of planting years. These parameters reached their maximum at the irrigation I2 (75–80% θFC) and slope S2 (6.38°) treatments. Thus, based on the results of this study, medium irrigation I2 (75–80% θFC) and slope S2 (6.38°) should be considered as the best slope and water management strategy to obtain both high Panax notoginseng yield and economic benefits. Through establishing a multi-objective optimization model with binary quadratic regression analysis. It was indicated that Panax notoginseng yield, WUE, PFP, and economic benefits simultaneously reached ≥ 98% of their maximum values when irrigation interval was 152–193 mm and slope interval was 5.4–9°. In summary, the results obtained in this study have important practical significance for the water management of Panax notoginseng cultivation in slope farmland in Yunnan Province, China.

Influence of Interlayer Soil on the Water Infiltration Characteristics of Heavy Saline–Alkali Soil in Southern Xinjiang

Interlayer soil is common in southern Xinjiang, because interlayer can reduce the infiltration rate of soil water. To simulate the interlayer soil in heavy saline–alkali cotton fields, this paper adopted a vertical one-dimensional infiltration test. T1 (315 mm), T2 (270 mm), and T3 (225 mm) and different interlayer positions (T5, 315 mm) and thicknesses of the interlayer (T6, 315 mm) with the same irrigation volume, as well as one perforation and sand filling treatment (T4, 315 mm), were set. The influence of different irrigation amounts, locations, and thicknesses of the interlayer and sand injection on water infiltration was analyzed. The analysis results showed that with the increase in irrigation amount, the water infiltration rate and the migration distance of the wet front increased, but did not penetrate to the bottom soil (90 cm). Under the same irrigation volume, the increase in interlayer thickness (T6) compared with the increase in interlayer position (T5), the change in soil moisture content in the upper and lower layers of the interlayer was greater, and the advance time of wetting front migration and cumulative infiltration were slightly higher. After tunneling and sand filling (T4), the infiltration rate of water was increased, the migration time of the wet front was reduced, and the profile water content of each soil layer was improved. The Kostiakov model could better simulate the water infiltration characteristics of interlayer soil with different profile configurations in heavily saline–alkali land. The results showed that in all of the treatments, only the wet front of the soil moisture reached 100 cm in the T4 treatment, and the maximum was only 87.8 cm in the other treatments, indicating that too little irrigation water or the upward movement and thickening of the interlayer were not conducive to water infiltration. For the interlayer soil area in the heavy saline–alkali land in southern Xinjiang, the appropriate irrigation water should be more than 315 mm. The treatment of drilling first and then filling sand can be used as a simple but effective measure to increase the water infiltration rate of the interlayer soil, and can thus be applied to the layered soil structure in the interlayer position of 60–80 cm.

Optimization of Subsurface Drip Irrigation Schedule of Alfalfa in Northwest China

Determination of an optimum irrigation amount and buried depth of subsurface drip irrigation laterals is significantly important in improving crop yield and irrigation water using efficiency in arid regions. In this study, the effects of three irrigation volumes (15.0, 22.5 and 30.0 mm) and three burial depths (10, 20 and 30 cm) of drip laterals on water consumption, yield and water productivity of alfalfa were investigated in a field trial. The water balance equation and FAO-56 crop coefficient methods were applied to determine the evapotranspiration of alfalfa. The results showed that the alfalfa evapotranspiration estimated by the dual crop coefficient method was closer to the actual measured values. The alfalfa water consumption, yield and water productivity increased significantly (p &lt; 0.01) with the increase in irrigation amount, but the increasing trend turned to decrease (p &lt; 0.05) with the increase of the buried depth of the drip irrigation laterals. During the whole growing period of alfalfa, the total water consumption ranged from 400 to 500 mm, the total yield ranged from 7500 to 12,000 kg/hm2 and the water productivity was 1.80 to 2.50 kg/m3. An optimized irrigation amount of 22.5 to 30.0 mm for an irrigation event with a frequency of 5 to 7 days using buried drip irrigation with an irrigation lateral depth of 20 cm was recommended for alfalfa in the study area.

Determining the plant critical saturated water accumulation curve in maize

Water scarcity is one of the major factors limiting crop growth and productivity. Judicious water management reduces the application of irrigation water and increases grain yield, farm profits, and water use efficiency . The assessment of crop water status is the key to in-season irrigation scheduling . The plant diagnostic approach has the potential to assess the in-season crop water status for optimizing crop water use. For this purpose, a series of field and rainout shelter experiments with varying amounts of irrigation water (0–275 mm for field and 0–315 mm for rainout shelter experiments) and planting densities (6–8 ×10 4 plants ha −1 ) using seven maize cultivars were conducted from the 2017–2020 growing seasons in North China Plain to determine and validate the plant critical saturated water accumulation (SWA) curve during the vegetative growth period of maize. The result showed that the plant dry mass (DM) and the SWA ranged from 0.07 to 8.22 t ha −1 and 0.63–59.06 t ha −1 during the vegetative growth period of maize, respectively. The plant DM and SWA increased with the increase in irrigation amount. However, plant DM and plant SWA showed non-significant differences under non-water-limiting conditions. An allometric relationship between plant DM and plant SWA was used to develop the plant critical SWA curve (SWA = 8.26DM 0.89 , R 2 =0.98 ** ). A plant water diagnosis index (WDI) was then derived using the critical SWA curve to quantitatively assess the in-season water status of maize. The WDI increased with the increase of irrigation amount and ranged from 0.72 to 1.26 with a value of 1, indicating an optimum plant water status. The newly developed curve could diagnose and categorize the water-limiting and non-water-limiting plant water status and can be employed for precision irrigation management during maize cultivation.

Effect of Irrigation Pattern and Irrigation Level on Growth of Glycyrrhiza inflata and the Medicinal Quality of its Root

Background: Although both the root and rhizome of Glycyrrhiza inflata have been used as medicinal material, the sales volume and price of its root are much higher than its rhizomes. Limiting the growth of liquorice rhizomes while improving the yield and quality of its root has become an important problem. Methods: Two irrigation patterns (surface drip irrigation and subsurface drip irrigation, i.e. DI and SDI) and three irrigation levels (40%-50%, 60%-70% and 80%-90% of the maximum soil water capacity) were used in this study. Result: The plant height, crown width, root length, root biomass and concentrations of the five medicinal components (glycyrrhizic acid, glycyrrhetinic acid, glycyrrhizin, liquiritigenin and isoliquiritigenin) of the SDI treatments were significantly higher than those of the DI treatments. The above parameters reached their maximum under the SDI90 treatment (SDI with 80%-90% of the maximum soil water capacity). The rhizome growth of the liquorice was promoted with an increase in irrigation amount, but the biomass of the rhizomes under SDI treatment was significantly lower than that under DI treatment. Thus, the regime of SDI with a relatively high water supply can effectively promote the yield and medicinal quality of liquorice roots, while inhibiting the development of its rhizomes.

Effect of drip-line layout and irrigation amount on yield, irrigation water use efficiency, and quality of short-season tomato in Northwest China

Greenhouse tomato cropping with under-mulch drip irrigation is common in arid and semi-arid Northwest China. To investigate the influence of drip-line layout and irrigation amount on yield, fruit quality, irrigation water use efficiency, and comprehensive benefit of tomato production, the experiment was conducted during two cropping seasons of spring to summer in 2015 and winter in 2015 to spring in 2016. In these two cropping seasons, two drip-line layout types were conducted, including a one drip-line for each plant-row and a one drip-line for two plant-rows, with four levels of irrigation amount, i.e., 0.6, 0.8, 1.0, and 1.2 times of accumulated evaporation of a 20 cm standard pan. The results showed that one drip-line for two plant-rows outperformed one drip-line for each plant-row in achieving higher yield and irrigation water use efficiency with the same irrigation amount. In these two drip-line layouts, tomato yield increased at first and then decreased with the increase of irrigation amount; while irrigation water use efficiency decreased all the way with the increase of irrigation amount. A principal component analysis demonstrated that the combination of one drip-line for each plant-row and 1.0 times of pan evaporation obtained the highest comprehensive fruit nutritional quality among all combinations of drip-line layout and irrigation amount in spring-summer season; while the combination of one drip-line for two plant-rows and 0.8 times of pan evaporation had the highest comprehensive fruit quality in winter-spring season. To purse high comprehensive benefits, combinations of one drip-line for two plant-rows and 0.8 times of pan evaporation, and one drip-line for each plant-row and 0.6 times of pan evaporation should be recommended for spring-summer and winter spring cropping seasons, respectively. The findings of this study can provide irrigation guidance for greenhouse tomato growing in Northwest China.

Optimizing irrigation amount and potassium rate to simultaneously improve tuber yield, water productivity and plant potassium accumulation of drip-fertigated potato in northwest China

High crop water productivity (WPc) and fertilizer use efficiency are the key to ensuring the sustainable development of agriculture in water-deficient areas, such as the northwest China. In order to determine the irrigation amount and potassium rate for optimizing potato yield, plant potassium accumulation and WPc of drip-irrigated potato, a two-year field experiment was conducted on the Loess Plateau of northwest China, with three irrigation levels (W1: 60% ETc, W2: 80% ETc and W3: 100% ETc, where ETc is the crop evapotranspiration) and four potassium levels (K0: kg ha−1, K1: 135 kg ha−1, K2: 270 kg ha−1 and K3: 405 kg ha−1). The results showed that leaf area index, chlorophyll content, aboveground dry matter, tuber yield, starch, vitamin C content and WPc generally increased with the increase of irrigation amount, while they first increased and then decreased with the increasing potassium rate. The trends of reducing sugar and potassium use efficiency were contrary to the above trends. The residue of available potassium in the soil increased with the increase of potassium rate, but decreased with the increase of irrigation amount. Irrigation amount and potassium rate had interaction effects on chlorophyll content, dry matter, tuber yield, reducing sugar, plant potassium accumulation and potassium use efficiency. To ensure high-yield, high-quality, water-saving and fertilizer-saving potato production, a water input (irrigation plus effective rainfall) range of 498–520 mm combined with a potassium rate range of 201–393 kg ha−1 was recommended. These results can provide a theoretical basis for the rational application of irrigation water and potassium fertilizer to improve tuber yield, quality and soil environment of drip-irrigated potato in northwest China.

Effects of water saving and nitrogen reduction on the yield, quality, water and nitrogen use efficiency of Isatis indigotica in Hexi Oasis

Isatis indigotica planting is the backbone of the medicinal industry in Hexi Oasis, Gansu. In order to solve the problems insufficient water resources and excessive application of nitrogen fertilizer in this area, this paper explored the irrigation and nitrogen levels that can meet the multiple goals of Isatis indigotica. The two-factor split-plot field experiment (2018‒2019) was conducted in Minle County, Gansu Province, China, which contains 9 treatments. There were three levels of irrigation water: W1(low), W2(medium), and W3(high). The soil moisture contents were 60–70%, 70–80%, and 80–90% of the field water-holding capacity, respectively. The nitrogen application rate was classified into three levels, N1(low), N2(medium) and N3(high), which were 150, 200 and 250 kg N/ha, respectively. The standard local irrigation water amount and nitrogen application rate corresponded to W3N3. The results showed that the yield of Isatis indigotica increased first and then decreased with the increase of irrigation amount and nitrogen application rate, the yield of W2N2 is 12.2–17.1% higher than that of W1N1, the yield of W3N3 was 12.1–17.5% lower than that of W2N2. Saving water and reducing nitrogen can improve the quality of Isatis indigotica, compared with W3N3, the indigo, indirubin, (R,S)-epigoitrin and polysaccharides of W2N2 increased by 4.5–5.9%, 2.7–3.1%, 5.2–6.0%, and 1.8–2.1%, respectively. With the increase of nitrogen application rate, the water use efficiency (WUE) first increased and then decreased, as the irrigation volume increases, WUE decreases. Compared with W3N3, the WUE of W2N2 increased by 24.3–27.2%. With the increase of water input, the nitrogen fertilizer use efficiency (NUE) first increased and then decreased, as the nitrogen application rate increases, NUE decreases. Compared with W3N3, the NUE of W2W2 increased by 31.8–34.5%. Therefore, W2N2 can improve quality and increase water and nitrogen utilization efficiency on the basis of ensuring yield.

Nitrogen distribution in apple orchard soil profile under fertilization with different water and fertilizer coupling techniques

Optimization of water and fertilizer coupling management approaches could not only increase apple yield and quality, but also reduce the potential negative impacts of such management activities on the environment. The aim of the present study was to determine the optimal water-nitrogen (WN) coupling management strategy in an apple orchard in the Weibei Dryland, Shaanxi Province, China, under limited irrigation. A randomized complete block design was adopted to test the effects of three drip irrigation levels (W1, 300 m3/hm2; W2, 600 m3/hm2; W3, 900 m3/hm2) and four N application levels (N0, 0 kg/hm2; N1, 200 kg/hm2; N2, 400 kg/hm2; and N3, 600 kg/hm2) on N distribution in the 0-100 cm soil profile. Apple yield and economic benefits under different treatments were also evaluated over a three-year period (2012-2014). Compared with the N0W1 treatment, soil N contents were higher and exhibited distinct trends in the soil profile under other treatments. Overall, total N contents exhibited a downward trend from the surface to the subsurface layers (0.11-2.34 g/kg); however, the total N contents of the lower soil layer increased with an increase in irrigation amount. NO3-N contents were the lowest in the 40- 60 cm soil layer and then increased with an increase in soil depth. The highest NO3-N contents of different soil layers were observed under the N3W3 treatment, ranging from 124.7 mg/kg (0-20 cm) to 90.9 mg/kg (80-100 cm). NH4+-N contents were low ( 20 cm. Different water-N coupling treatments also increased apple yield by 7.30%-41.62% when compared with the N0W1 treatment. The highest apple yield (three-year mean: 41.01 t/hm2) was observed under the N2W2 treatment, with an output value of 237 900 RMB yuan/hm2 and a net income of 232 000 RMB yuan/hm2. Considering fruit yield, partial productivity of N fertilizer, and economic and environmental benefits, the N2W2 treatment is the optimal water-N fertilizer coupling drip irrigation scheme for apple production in the study area and other similar dryland areas. Keywords: apple orchard, water-nitrogen coupling, nitrogen fertilization, soil profile, yield DOI: 10.25165/j.ijabe.20221505.7257 Citation: Zhao Z P, Yan S, Hu S Y, Qu K J, Tong Y A. Nitrogen distribution in apple orchard soil profile under fertilization with different water and fertilizer coupling techniques. Int J Agric & Biol Eng, 2022; 15(5): 146–154.

Water use efficiency and nitrogen use efficiency of apical rooted cuttings of potato grown in a mollic Andosol

AbstractWater and nitrogen (N) are key interacting factors that control plant growth. The objective of the study was to determine the effect of N rates and drip irrigation regimes on water use efficiency (WUE) and N use efficiency (NUE) of apical rooted cuttings of potato (Solanum tuberosum L.) grown in a mollic Andosol. The treatments comprised four drip irrigation regimes of 50%, 75%, 85% and 100% of the crop evapotranspiration (ETC), where ETC100% was irrigated according to the soil water depletion 2 d after full irrigation and four N rates: 0 (N0), 60 (N1), 90 (N2) and 130 kg N ha−1 (N3). The results showed that potato tuber yield, WUE, and NUE were significantly (P &lt; .001) affected by irrigation regimes, N rates, and the interaction of both factors. The highest potato tuber yield, 58.29 Mg ha−1, was obtained under ETC100% with N3, whereas the highest WUE, 17.5 kg m−3, was found under ETC50% with N3. The apical rooted cuttings of potato grown under ETC100% with N2 produced the maximum NUE, 208.30 kg kg−1. The correlation coefficient (r = 0.31; P &lt; .01) obtained between WUE and NUE was weak. It was also observed that an increase in irrigation amount decreased WUE and increased NUE, whereas a high N dosage increased WUE and decreased NUE of potato grown in a mollic Andosol. This study suggests that if the farmers aim to maximize NUE of apical rooted cuttings in a mollic Andosol, then they will do so at the expense of potato WUE, and yield will be looked at as a secondary factor.

Quantifying grain yield, protein, nutrient uptake and utilization of winter wheat under various drip fertigation regimes

Nitrogen (N), phosphorus (P) and potassium (K) are essential elements for crop growth. The absorption, accumulation process and distribution of these nutrients affect not only the growth and grain yield, but also the grain quality of wheat (Triticum aestivum L.). Various fertilization and irrigation practices can influence wheat growth as well as the absorption and utilization of nutrient elements. A four-season (2014–2018) experiment was conducted on drip-fertigated winter wheat on the Loess Plateau of China with three irrigation levels and three fertilization rates. Irrigation rates included normal irrigation (W1), mild deficit irrigation (W2) and more severe deficit irrigation (W3), while fertilization rates (N-P2O5-K2O) included F1 (175–117–150 kg ha−1), F2 (125–84–108 kg ha−1) and F3 (75–50–65 kg ha−1). The results showed that NPK uptake in aboveground biomass decreased as the water stress increased, but there was no significant difference between W1 and W2. When sufficient water and fertilizer were applied, the stem, leaf and rachis + glume obtained higher proportion of NP, while grain nitrogen and phosphorus harvest index (NHI and PHI) decreased. When the supply of water and fertilizer was insufficient, NHI and PHI increased, and the proportion of vegetative organs was relatively low. The average NPK requirement for 100 kg grain (GNR, GPR and GKR) varied 1.93–3.03, 0.37–0.41 and 2.26–2.93 kg over the four seasons. GNR and GKR increased with increasing irrigation and fertilization regimes. With the increase of irrigation amount, irrigation water use efficiency (IWUE) first increased and then decreased slightly, and the maximum IWUE occurred under W2. Yield and IWUE increased with the increase of fertilization rate, but there was no significant difference between F1 and F2. F2 obtained higher partial factor productivity than F1. F1 and F2 had no significant difference in protein content and protein yield, but they obtained significantly higher values than F3. Therefore, W2F2 was an efficient water and fertilizer management practice for drip-fertigated winter wheat, which promoted nutrients transfer to grains without significantly reducing grain yield and protein.

Responses of yield, quality and water-nitrogen use efficiency of greenhouse sweet pepper to different drip fertigation regimes in Northwest China

Given water resources scarcity in Northwest China and the urgent need for the integration and optimization of scientific and technological resources in facility agriculture, this experiment explored the appropriate water and fertilizer management measures for greenhouse sweet pepper under fertilization in Northwest China. A two-year drip fertigation sweet pepper experiment was conducted in a solar greenhouse, with four irrigation levels (W1: 105% ETC, W2: 90% ETC, W3: 75% ETC, W4: 60% ETC) and four nitrogen levels (N1: 300 kg/ha, N2: 225 kg/ha, N3: 150 kg/ha, N4: 75 kg/ha). The results showed that above-ground dry matter accumulation (DMA), yield, harvest index (HI), and water use efficiency (WUE) of sweet pepper increased first and then decreased with the increase of irrigation/nitrogen amounts under the same nitrogen/irrigation levels. The partial factor productivity of nitrogen (PFPN) decreased significantly with the increase of nitrogen application rate, while it increased first and then decreased with the increase of irrigation level. The PFPN reached a peak at W2 level, despite no significant difference between W2 and W3 levels. With the increase of nitrogen application rate, soluble sugar and vitamin C content increased first and then decreased with a maximum at N3 level; nitrate content increased with the increase of nitrogen application rate, and there was no significant difference between N4 and N3 levels. The contents of soluble sugar and nitrate nitrogen decreased with the increase of irrigation amount, and they did not differ between W1 and W3 levels at N3 level; the vitamin C content increased first and then decreased with the increase of irrigation amount, reaching the maximum in W2 or W3 treatments. Considering the shortage of water resources in the study area, the W3N3 treatment (75% ETC, 150 kg/ha) could be recommended as the optimal drip fertigation strategy. Results showed that the optimal value of sweet pepper (the best confidence intervals of 85%) was achieved at the irrigation water and nitrogen amount of 78.2–80.8% ETC and 164.5–189.5 kg/ha, respectively. This study provides scientific basis for water and nitrogen management of high yield, quality, and benefit planting of facility sweet pepper in Northwest China.

Optimizing irrigation amount and fertilization rate of drip-fertigated spring maize in northwest China based on multi-level fuzzy comprehensive evaluation model

The arid and semi-arid region of northwest China is an important region for spring maize production in China, but improper water and fertilizer management has caused ecological problems in these regions. A two-year field experiment was conducted in 2015 and 2016 in the Gansu Province of China to investigate the effects of different irrigation amounts and fertilization rates on growth, grain yield, water and fertilizer use efficiency, and soil nutrient residue of drip-fertigated spring maize, and explore the optimal combination of irrigation amount and fertilization rate based on a multi-level fuzzy comprehensive evaluation (MFCE) model. The irrigation levels included I60 (60% of crop evapotranspiration), I75, I90 and I105 in 2015 and I60, I80, I100 and I120 in 2016. The N-P2O5-K2O fertilization rates (kg ha−1) were F60–30–30, F120–60–60, F180–90–90 and F240–120–120. The results showed that plant height, stem diameter and leaf area index were highest under F240–120–120. Maize yield, dry matter, water use efficiency (WUE) followed a upward opening parabola with irrigation amount and fertilization rate, and reached the maximum under I90F180–90–90 in 2015 and under I100F180–90–90 in 2016. With the simultaneous increase in irrigation amount and fertilization rate, nitrate nitrogen content in the 60–120 cm soil layer showed an increasing trend. Based on the MFCE model, the irrigation amount of 415–450 mm combined with the N-P2O5-K2O rate of 144–77–77 to 180–90–90 kg ha−1 obtained the optimal comprehensive benefit of maize growth, economic return, water and fertilizer utilization and environmental benefit. This work can provide a scientific basis for the optimization and management of spring maize irrigation and fertilization in northwest China.

Evaluation of cotton N nutrition status based on critical N dilution curve, N uptake and residual under different drip fertigation regimes in Southern Xinjiang of China

Irrigation and fertilization are the two most important measures to ensure the agricultural development in arid regions. However, there is still a lack of reasonable irrigation and fertilization strategy in Xinjiang, the largest cotton producing area in China, which causes a waste of resources and a reduction in cotton yield and pollutes the environment. This study investigated the effects of four irrigation amounts (W0.6: 60% ETc, W0.8: 80% ETc, W1.0: 100% ETc and W1.2: 120% ETc, where ETc is the crop evapotranspiration) and four nitrogen rates (N250-250 kg N ha-1, N300-300 kg N ha-1, N350-350 kg N ha-1 and N400-400 kg N ha-1) on seed cotton yield, nitrogen nutrition status and soil nitrogen residue, so as to explore the optimal water-nitrogen coupling strategy to increase cotton production and water-fertilizer use efficiency while reducing environmental pollution. The nitrogen dilution curves were built to assess the nitrogen nutrition status of cotton. The results showed that increasing irrigation amount increased dry matter and seed cotton yield, but decreased harvest index. Nitrogen application enhanced the nitrogen concentration and accumulation in cotton. Irrigation decreased the nitrogen concentration, but increased the nitrogen accumulation by increasing the dry matter. The highest total plant nitrogen accumulation was obtained under W1.2N400, 223.88 kg ha-1 in 2018 and 242.77 kg ha-1 in 2019. With the increase of irrigation amount, agronomic nitrogen utilization efficiency (aNUE) first increased and then decreased. Increasing irrigation amount increased nitrogen recovery efficiency (NRE), but reduced physiological nitrogen utilization efficiency (pNUE). pNUE and aNUE decreased with the increasing nitrogen rate, while NRE first increased and then decreased. Soil NO3−-N content increased with the increase of nitrogen rate. Irrigation reduced NO3−-N content in the surface soil (0–30 cm), while increased that in the deeper soil (40–80 cm). The optimal nitrogen nutrition status was found under W1.0N300, followed by W1.0N350. Furthermore, the optimal dry matter, seed cotton yield, NRE and total nitrogen accumulation were obtained under W1.0N350, which was considered as the optimal combination of irrigation amount and nitrogen rate in this study.

Optimal irrigation amount and nitrogen rate improved seed cotton yield while maintaining fiber quality of drip-fertigated cotton in northwest China

Improving the quality of cotton fiber is an important way to increase the competitiveness of cotton in the international market. However, how to improve fiber quality as much as possible without significantly reducing seed cotton yield is still a challenge to the cotton industry. A two-year field experiment was conducted in 2018 and 2019 to investigate the effects of irrigation amount and nitrogen rate on seed cotton yield and fiber quality traits of drip-fertigated cotton in northwest China. A comprehensive evaluation model was also developed to determine the optimal supply range of water and nitrogen to simultaneously improve seed cotton yield and fiber quality. There were four irrigation amounts (W0.6-60 % ETc, W0.8-80 % ETc, W1.0-100 % ETc and W1.2-120 % ETc, ETc was the crop evapotranspiration) and four nitrogen rates (N250-250 kg N ha−1, N300-300 kg N ha−1, N350-350 kg N ha−1 and N400-400 kg N ha−1). Increasing irrigation amount and nitrogen rate had positive effects on seed cotton yield. However, there was no significant difference in seed cotton yield between W1.0 and W1.2 and between N350 and N400. The optimal seed cotton yield was obtained under W1.0N350 in both 2018 (6655.58 kg ha−1) and 2019 (6309.3 kg ha−1). Water use efficiency (WUE) increased with the increase of nitrogen rate, and decreased with the increasing irrigation amount. Nitrogen partial factor productivity (PFPN) increased with the increase of irrigation amount, and decreased with the increasing nitrogen rate. There was a positive correlation between irrigation amount and fiber length, fiber strength, fiber quality index (FQI) and textile parameter, but a negative correlation with micronaire and short-fiber index. Fiber length, fiber strength, FQI and textile parameter first increased and then decreased with the increasing nitrogen rate. Irrigation amount and nitrogen rate had no significant effect on maturity index. There were strong correlations between the results of various evaluation methods, but the ranking differed among the methods. Based on the comprehensive evaluation model, the optimal combination of irrigation amount and nitrogen rate was W1.0N350. Through the combination of multiple regression and spatial analysis, the optimal supply range of irrigation amount of 334∼450 mm and nitrogen rate of 320∼400 kg ha−1was able to obtain over 90 % of the optimal seed cotton yield and 80 % of the optimal fiber quality.