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Grain‐filling rate and duration largely affect the grain‐filling capacity, which determines the grain yield of maize (Zea mays L.). Nevertheless, there is little about the mechanism of how various soil mulching practices affect the leaf photosynthetic potential and subsequent grain‐filling capacity of maize. Field experiments were undertaken on rainfed summer maize in northwest China under flat cultivation without mulch (FNM), flat cultivation with straw mulch (FSM), flat cultivation with transparent film mulch (FTF), flat cultivation with black film mulch (FBF), ridge‐furrow cultivation with transparent film mulch (RTF) and ridge‐furrow cultivation with black film mulch (RBF) in 2021 and 2022. This study explored the impact of various soil mulching patterns on soil hydrothermal condition, leaf growth, photosynthetic potential, aboveground dry matter growth and grain‐filling process of rainfed maize. The dynamics of leaf area index (LAI) and grain‐filling were fitted with growth equations, and the relationships of grain‐filling rate, leaf area duration and LAI withering rate were quantified. The results showed that, compared with FNM, other five soil mulching practices improved soil hydrothermal condition, the maximum LAI and leaf expansion rate but reduced leaf withering rate, thereby increasing radiation interception rate (RI) at the grain‐filling stage. The soil mulching practices also increased leaf SPAD value, net photosynthetic rate, photosynthetic nitrogen use efficiency and the aboveground dry matter. Compared with FNM, other five practices extended the effective grain‐filling period and the active period of grain‐filling, increased the maximum and mean grain‐filling rates, improved the 100‐kernel weight and the average kernel per ear (KPE), thereby increasing grain yields by 9.2%, 33.7%, 38.0%, 46.3% and 58.6%, respectively. The functional relationships of grain‐filling rate and accumulated leaf area duration (y = a/(1 + b*exp(−kx))), and the functional relationships of grain‐filling rate and LAI withering rate (y = (a + cx + ex2)/(1 + bx + dx2)) were first proposed. In conclusion, various soil mulching practices improved the soil hydrothermal condition, green leaves growth process and RI, which improved the leaf photosynthetic potential and the grain‐filling capacity, thereby increasing the 100‐kernel weight, KPE and grain yield. This study can help us quantitatively describe and better understand the maize grain‐filling process under various mulching practices. [ABSTRACT FROM AUTHOR]

Water stress can trigger acclimation responses and damage plants. The aim of this study was to evaluate the integrative responses of cotton hydraulic conductance, leaf photosynthesis, and carbon metabolism to short-term drought and subsequent rewatering. A water-controlled pot experiment was conducted in 2020, with soil water drying continuing for one day (D1), two days (D2), and three days (D3) after it reached 40% ± 5% of the soil water holding capacity at the blooming stage of cotton, and the soil was then rewatered to the soil water holding capacity. We investigated how the stem hydraulic conductance, gas exchange, and biochemical traits of cotton were affected by imposed drought stress and subsequent rewatering. The hydraulic characteristics of cotton in the D2 and D3 treatments evolved with damage, complete closure of stomatal conductance, and complete deterioration of photosynthesis, in addition to severe floating changes in the carbon metabolism affected by drought. The leaves' functional characteristics after rewatering cannot be completely recovered to full-irrigation levels, and the recovery extent was strongly linked to the duration. Consequently, it is considered desirable to maintain normal physiological activity during the cotton reproductive period, and the drought episode can be sustained for 1 day in a long-term perspective when the soil water content is depleted to 40% ± 5% of the soil water holding capacity. These results can provide in-depth ideas for better understanding the hydraulic and physiological responses of cotton to drought episodes and rewatering, and they can help drought-affected cotton to cope with future climate change. [ABSTRACT FROM AUTHOR]

Soil mulch has been widely applied to enhance crop yields in (semi-)arid and semi-humid regions on the globe. However, how different mulch practices influence root growth, plant nitrogen (N) uptake, remobilization and allocation remains unclear, especially under different N fertilization rates. A two-season (June–October in 2021 and 2022) field experiment was performed on dryland summer maize in a semi-humid but drought-prone region of northwest China. There were six mulch practices: flat cultivation without mulch (Flat), flat cultivation with straw mulch (Flat-Straw), flat cultivation with black film mulch (Flat-Film), flat cultivation with transparent film mulch (Flat-Trans), ridge-furrow cultivation with black film mulch on the ridge (Ridge-Film), ridge-furrow cultivation with transparent film mulch on the ridge (Ridge-Trans), and two N fertilization rates: 0 kg N ha−1 (N0) and 180 kg N ha−1 (N1). The results showed that film mulch significantly (p <0.05) improved root morphological parameters compared to Flat. Plant N uptake significantly (p <0.05) increased due to improved root growth under film and straw mulch, with grain N uptake increasing by 78.2% under Ridge-Film, 66.2% under Ridge-Trans and 39.6% under Flat-Film compared to Flat. The significant (p <0.01) increases in pre-anthesis N remobilization and post-anthesis N uptake under film and straw mulch compared to Flat achieved synergistic increases in grain yields. The contributions of total N remobilization to grain N dramatically increased by 31.2%, 27.5%, 17.0% and 11.2% under Ridge-Film, Ridge-Trans, Flat-Film and Flat-Trans compared to Flat, respectively. Meanwhile, film-mulched practices significantly (p <0.01) reduced soil nitrate-N residual due to improved plant N uptake, by 21.7% under Flat-Film, 16.9% under Flat-Trans, and 33.6% under Ridge-Film compared to Flat. The contributions of various mulch practices to grain yield ranked as Ridge-Film > Flat-Film > Ridge-Trans > Flat-Trans > Flat-Straw. The Ridge-Film with N fertilization significantly (p <0.05) increased N use efficiency, N agronomic efficiency, N recovery efficiency, N harvest index and grain yield by 10.8%, 124.9%, 147.1%, 19.8% and 120.0% compared to FlatN0, respectively. The structural equation modeling indicated that the differences in post-silking N uptake and pre-silking N remobilization caused by different mulch practices and nitrogen rates could directly explain at least 48.0% and 52.0% of grain yield differences. The ridge-furrow cultivation with film mulch, especially black film mulch, along with 180 kg N ha−1 is favorable for improving grain yield and N use efficiency of dryland summer maize in the semi-humid but drought-prone region of northwest China. • Mulching practices increased pre-anthesis N remobilization and post-anthesis N uptake. • Ridge-furrow planting with black film mulching significantly increased nitrogen use efficiency. • Mulching practices increased grain yield of maize and reduced soil nitrate-N residue. • Ridge-furrow plastic film mulching with 180 kg N ha−1 is favorable for maize production. [ABSTRACT FROM AUTHOR]

Plant density and nitrogen (N) rate are two important factors affecting maize yield. However, the interacting effects of plant density and nitrogen rate on maize production and water productivity are still poorly understood, especially under drip irrigation conditions. A two-year field experiment was carried out to determine the interactive effects of plant density and N rate on grain yield, economic benefit, water productivity (WP) and nitrogen use efficiency of drip-fertigated spring maize (Zea mays L.) in northwest China. Based on the local plant density of 80,000 plants ha-1 and N rate of 240 kg ha-1, two plant densities (D1: 80,000 plants ha-1, D2: 100,000 plants ha-1) and four N rates (N0: 0, N120: 120 kg ha-1, N180:180 kg ha-1, N240: 240 kg ha-1) were set in 2018, while a higher plant density (D3: 120,000 plants ha-1) was further considered in 2020. The results showed that grain yield, economic benefit, WP and nitrogen use efficiency were significantly affected by plant density, N rate and their interaction (except for economic benefit). Average grain yield increased and then decreased with increasing N rate under D1 and D2 with the maximum values under N180 in both 2018 (12,193 kg ha-1 and 16,650 kg ha-1) and 2020 (11,136 kg ha-1 and 15,093 kg ha-1), while it continued to increase as N rate increased under D3 in 2020. On average, D2 produced significantly higher grain yield than D1 in both 2018 (13,464 kg ha-1 and 10,477 kg ha-1) and 2020 (13,268 kg ha-1 and 9,859 kg ha-1), while grain yield under D2 (13,366 kg ha-1) was significantly higher than that under D3 (12,301 kg ha-1) and D1 (10,168 kg ha-1) in 2020. Similar trends to grain yield were also obtained for economic benefit. Overall, grain yield, economic benefit, WP and N partial factor productivity under D2N180 was significantly increased by 41.6%, 52.6%, 33.8% and 90.4% compared with those under the conventional management practice (D1N240), respectively. Based on the multiple regression and spatial analysis, the optimal ranges of plant density of 95,000∼110,000 plants ha-1 and N rate of 185∼205 kg ha-1 were able to simultaneously obtain ≥95% of the maximum grain yield, economic benefit and water productivity. • Medium density (100,000 plants ha-1) produced greater yield than low and high (80,000 and 120,000 plants ha-1) densities. • Maize yield peaked at 180 kg N ha−1 under low and medium densities, while at 240 kg N ha−1 under high density. • Medium density with 180 kg N ha−1 improved maize yield, economic benefit and water productivity. • Comprehensive benefit was obtained with 95,000~110,000 plants ha-1 and 185∼205 kg N ha−1. [ABSTRACT FROM AUTHOR]

Understanding the spatial distributions of soil water, temperature and nutrients as well as their effects on maize growth and grain yield is vital for optimizing drip fertigation regimes. In this study, a 2 year field experiment was conducted on drip-fertigated spring maize with plastic mulching in arid northwestern China in 2015 and 2016. Four irrigation levels were set: as I60 (60% ETc; ETc is crop evapotranspiration), I75 (75% ETc), I90 (90% ETc) and I105 (105% ETc) in 2015; and as I60 (60% ETc), I80 (80% ETc), I100 (100% ETc) and I120 (120% ETc) in 2016. Two fertilization rates of N-P2O5-K2O were set: as F180 (180-90-90) and F240 (240-120-120). The results showed that the average soil water content in the deeper soil layer (80–120 cm) increased with the increase in irrigation level, and the lowest average soil water content in the 0–80 cm soil layer occurred under I95 in 2015 and under I100 in 2016. The irrigation level more significantly influenced the soil temperature at 5 cm than at the other depths. With the decrease in the irrigation level and progression of the growth period, the soil temperature increased. The soil nitrate nitrogen content in the root zone decreased with increasing irrigation level. The largest soil nitrate nitrogen content at the 0–100 cm depth occurred under I60 in both 2015 and 2016. Significant differences were observed for root length density in the 0–20 cm soil layer at various lateral locations. In deeper (60–100 cm) soil layers, the root length density under I75 (2015) and I80 (2016) was greater than at other depths. Grain yield, water use efficiency (WUE) and partial factor productivity (PFP) increased with the increase in irrigation level in 2015, while it increased and then decreased in 2016. I105F180 achieved the maximum grain yield (18.81 t ha−1), WUE (3.32 kg m−3), and PFP (52.26 kg kg−1) in 2015, while I100F180 achieved the maximum grain yield (20.51 t ha−1), WUE (3.99 kg m−3), and PFP (57.02 kg kg−1) in 2016. The optimal drip fertigation regimes for spring maize in arid northwest China were recommended as 90–100% ETc and 180-90-90 (N-P2O5-K2O) kg hm−2. [ABSTRACT FROM AUTHOR]

Ridge–furrow cropping patterns, nitrogen fertilisation and seed rate regulation are popular management strategies for improving crop yields in the semi‐arid areas of Northwest China, but their interactive effects on grain yield and water use efficiency remain poorly understood. In 2020–2021 and 2021–2022, a two‐season field experiment was conducted on winter wheat. There were two cropping patterns (C), ridge–furrow cropping with film mulch (RC) and traditional cropping without mulch (TC), two nitrogen fertilisation rates (N), 0 and 200 kg N ha−1 (N0 and N1) and three seed rates (S), 240, 360 and 480 plants m−2 (S1, S2 and S3). The study was conducted in a split–split design with three replications (randomised blocks) and a total of 24 experimental plots. It was found that the interactive effects of C × N, C × S and N × S were significant on soil temperature (ST), leaf area index (LAI), relative chlorophyll content (SPAD), photosynthetic parameters, grain yield (GY) and water use efficiency (WUE) (p < 0.05), while C × N × S was significant only for LAI, aboveground biomass (AGB), GY and WUE (p < 0.05). Compared with TC and N0, RC and N1 significantly increased SPAD value (2.4% and 15.8%), net photosynthetic rate (Pn) (19.8% and 32.8%), net photosynthetic rate (Pn), transpiration rate (Tr) (7.0% and 15.7%) and the effective PSII quantum production (ΦPSII) (10.7% and 5.0%). The highest GY (6773 kg ha−1 over 2020–2021 and 8036 kg ha−1 over 2021–2022) and WUE (20.03 kg ha−1 mm−1 over 2020–2021, and 21.77 kg ha−1 mm−1 over 2021–2022) of winter wheat were observed under RC + N1 + S2. The findings showed that the RC cropping pattern with fertilisation and seed rate regulation (360 plants m−2) of winter wheat, which is appropriate for ensuring the long‐term sustainability of agricultural production in the semi‐arid regions of Northwest China, enhanced plant growth, photosynthetic traits, yield and water use efficiency. The study might give useful information for enhancing the productivity and water use efficiency of winter wheat in this and other similar climate locations. [ABSTRACT FROM AUTHOR]

Ridge-furrow planting, supplementary irrigation and density regulation are effective measures to improve crop yields in (semi-)arid and drought-prone regions around the world, but their interactive effects on crop evapotranspiration, plant nitrogen uptake, grain yield and its components, water productivity, nitrogen use efficiency and economic benefit of winter wheat are not fully understood. Field experiments were carried out on winter wheat in a semi-humid but drought-prone region of northwest China during 2020 − 2021 and 2021 − 2022. There were two planting patterns (P): ridge-furrow planting with plastic film mulching on ridges (RF) and conventional flat planting (F), two supplementary irrigation amounts (I): 30 mm supplementary irrigation at both overwintering and returning-green stages (I 60) and no supplementary irrigation (I 0), and three planting densities (D): 240 × 104 plants ha−1 (LD), 360 × 104 plants ha−1 (MD) and 480 × 104 plants ha−1 (HD). The results showed that significant interactive effects of P × I, P × D, I × D and P × I × D on grain yield and water productivity of grain yield (WP g) were obtained, and the interactive effects of P × I, I × D and P × I × D on partial factor productivity of nitrogen (NPFP) and net income (NI) were significant. Compared with F, RF increased grain yield by 10.4%, WP g by 11.9%, water productivity of biomass yield (WP b) by 6.2%, precipitation and irrigation water use efficiency (PIUE) by 10.4%, irrigation water use efficiency (IUE) by 12.0%, agronomic nitrogen use efficiency (ANUE) by 5.3%, NPFP by 10.6% and NI by 17.1%. Compared with I 0 , I 60 increased grain yield by 13.5%, WP g by 7.8%, ANUE by 5.7%, NPFP by 13.7% and NI by 27.9%. Increasing planting density improved soil water consumption, population nitrogen uptake, effective number of panicles per unit area, WP b , PIUE, ANUE, NUtE and total income. Grain yield, WP g , NPFP and NI reached the maximum values at MD under RF, because the presence of plastic film in RF reduced the number of planting rows and resulted in excessive planting density in the plant row at HD compared to F. In summary, the optimized planting density (360 ×104 plants ha−1) combined with ridge-furrow planting and supplementary irrigation is more desirable for balancing grain yield, water productivity, nitrogen use efficiency and economic benefit of winter wheat in the semi-humid and drought-prone region of northwest China. ● Planting pattern, supplementary irrigation and planting density had interactive effects on grain yield. ● Ridge-furrow planting and supplementary irrigation increased grain yield, water-nitrogen use efficiency and net income. ● Grain yield, water-nitrogen use efficiency and net income were maximal at medium density under ridge-furrow planting. ● Grain yield, water-nitrogen use efficiency and net benefit were balanced under RFMDI 60. [ABSTRACT FROM AUTHOR]

Economic benefits and risk premiums significantly affect the production system decision making of farmers and government departments. This study evaluated the economic feasibility and estimated the risk premium of 12 rainfed soybean production systems with various planting densities, fertilization rates and planting patterns by considering the impact of soybean price fluctuation. There were two planting densities (D1: 160,000 plants ha−1 and D2: 320,000 plants ha−1), two fertilization rates (F1: 20 kg ha−1 N, 30 kg ha−1 P, 30 kg ha−1 K; F2: 40 kg ha−1 N, 60 kg ha−1 P, 60 kg ha−1 K) and three planting patterns (F+W0: flat cultivation with no irrigation; R+W0: plastic-mulched ridge-furrow cultivation (PMRF) with no irrigation; R+W1: PMRF with supplemental irrigation of 30 mm at the pod-filling stage). Based on the two-year (2019–2020) field data in a semi-humid drought-prone region of northwest China and soybean price fluctuation from January 2014 to June 2021, the net income (NI) was calculated by considering the impact of soybean price fluctuation and assuming constant soybean production costs. The net present value (NPV) method and the stochastic efficiency with respect to a function (SERF) method were used to evaluate the profitability of protective alternatives and the risk of these alternatives. The results showed that the 12 proposed soybean production systems were economically feasible. Reducing the fertilization rate reduced the input costs, but it did not necessarily result in a decrease in soybean yield and NI. The payback period of all production systems was within two years for farmers investing through loans. High-fertilizer and high-density production systems made personal investment obtain the highest economic benefit in this study, which was not the best investment strategy from the perspective of production-to-investment ratio and environmental protection departments. The preferences of farmers with various risk aversion and environmental protection departments in terms of risk premium were also proposed. The economic and risk assessment framework of this study can enhance the understanding of the adjustment of production systems from different perspectives, and provide strategies for promoting the protection of economic, environmental and socially sustainable agricultural systems. [ABSTRACT FROM AUTHOR]

Intercropping has great potential for alleviating arable land competition, improving land output and promoting sustainable agricultural development. However, the applicability of maize-soybean strip intercropping under drip fertigation in arid northwest China remains unclear, especially under various row configurations. A two-season (2022 and 2023) field experiment was performed in the Hexi Region of northwest China to investigate the responses of plant growth, yield performance, water-land productivity and economic profit of drip-fertigated maize-soybean strip intercropping systems to eight row configurations. The results showed that intercropping significantly reduced aboveground biomass accumulation of maize and soybean by 18.77% and 47.81% on average compared to monocropping, respectively. Intercropping significantly decreased the 100-grain weight, ear length and ear width of maize, and reduced the 100-grain weight and pod number of soybean, resulting in reduced grain yields of intercropped maize and soybean (by 13.08% and 48.73%, respectively), but two rows of maize alternating with four rows of soybean (M2S4), three rows of maize alternating with four rows of soybean (M3S4), four rows of maize in wide and narrow rows alternating with four rows of soybean (M4S4-MN), and four rows of maize in wide and narrow rows alternating with six rows of soybean (M4S6-MN) produced greater population grain yield compared to monocropping. Among all intercropping systems, the largest water-land productivity and economic profit occurred in M2S4 (1.61 in 2022 and 1.42 in 2023 for land equivalent ratio; 29.23 kg ha−1 mm−1 in 2022 and 28.22 kg ha−1 mm−1 in 2023 for water productivity; 23,965 CNY ha−1 in 2022 and 23,059 CNY ha−1 in 2023 for economic profit), followed by M4S4-MN (1.53 in 2022 and 1.36 in 2023 for land equivalent ratio; 27.11 kg ha−1 mm−1 in 2022 and 26.58 kg ha−1 mm−1 in 2023 for water productivity; 22,327 CNY ha−1 in 2022 and 22,224 CNY ha−1 in 2023 for economic profit). The M2S4 is thus the optimal row configuration for drip-fertigated maize-soybean strip intercropping systems in terms of grain yield, economic profit and land productivity, while the M4S4-MN is recommended by further considering the efficiency of mechanized sowing and harvesting. • Intercropping reduced maize and soybean aboveground biomass compared to monocropping. • Intercropping decreased maize and soybean grain yields by 13.08% and 48.73%, respectively. • Water-land productivity and economic profit peaked in two maize rows alternating with four soybean rows. • M2S4 and M4S4-MN are suitable for drip-fertigated maize-soybean strip intercropping. [ABSTRACT FROM AUTHOR]

Soil mulching has been widely used to improve crop productivity around the world, but how various mulching practices affect soil hydrothermal conditions, water-temperature-radiation utilization and finally grain yield of rainfed maize has been poorly understood. A two-season field experiment was conducted on rainfed summer maize in 2021 and 2022 on the Loess Plateau of China, with six soil mulching practices: flat planting with non-mulching (FPNM), flat planting with full straw mulching (FPSM), flat planting with full black film mulching (FPBF), flat planting with full transparent film mulching (FPTF), ridge-furrow planting with black film mulching on the ridge (RFBF) and ridge-furrow planting with transparent film mulching on the ridge (RFTF). The results showed that compared with the traditional FPNM, the five mulching treatments (FPSM, FPBF, FPTF, RFBF and RFTF) greatly regulated root-zone soil hydrothermal conditions and resulted in obvious soil drying-wetting alternation, which significantly changed the daytime average root-zone soil temperature in the 0 – 25 cm soil layer (by − 1.1 ℃, − 1.9 ℃, + 2.7 ℃, − 1.6℃ and + 0.8 ℃, respectively) and significantly reduced crop evapotranspiration. The five mulching treatments promoted the root growth, leaf area index and canopy light interception rate due to the improved soil water and/or temperature conditions. The structural equation modeling indicated that soil hydrothermal condition and water-temperature-radiation use efficiency could directly or indirectly explain 98% of the grain yield variation under various soil mulching practices; radiation use efficiency (RUE) determined maize production in the water-sufficient year (2021), whereas maize production was mainly determined by crop water productivity (WP) in the water-limited year (2022). The RFBF increased maize production most, followed by RFTF. Compared with FPNM, RFBF increased leaf area index by 45.4%, canopy light interception rate by 19.1%, aboveground biomass by 68.8%, 1000-grain weight by 15.1%, grain yield by 58.6%, WP by 71.8%, thermal time use efficiency by 64.6% and RUE by 30.5%. In conclusion, RFBF optimized the root-zone soil hydrothermal conditions for root growth, which in turn promoted aboveground growth and water-temperature-radiation use efficiency, and finally improved the gain yield of rainfed summer maize on the Loess Plateau of China. Therefore, RFBF was considered as a promising agricultural practice to improve rain-fed summer maize production and resource utilization efficiency on the Loess Plateau of China. • The warming effect of transparent plastic film may lead to negative effects for rainfed summer maize. • Ridge-furrow planting with black film mulching provided the optimal soil hydrothermal conditions. • Ridge-furrow planting with black film mulching increased water-temperature-light use efficiency. • Water productivity determined maize production in the dry year, not radiation use efficiency. [ABSTRACT FROM AUTHOR]

Soil mulching, e.g. straw mulching (SM) and ridge-furrow plastic film mulching (RP), has been reported to promote rainfed crop production in semi-arid regions, but its applicability in improving maize yield and especially yield stability in semi-humid drought-prone regions has been rarely explored. The capture and utilization of thermal, light, water and nutrients resources by maize plants under various soil mulching conditions are also poorly understood. A consecutive five-season field experiment was conducted on rainfed maize in a semi-humid drought-prone region of China during 2015–2019 to assess the effects of SM and RP on soil hydrothermal conditions, radiation interception, photosynthesis, evapotranspiration and grain yield stability, profitability and resources use efficiency compared with non-mulching (NM). The results showed that RP enhanced soil hydrothermal conditions, promoted the conversion of water from soil evaporation to plant transpiration and improved water productivity by 10.9%−203.2% compared with NM (P < 0.05). Although the growth duration was shortened, the accumulative soil thermal time and intercepted photosynthetically active radiation under RP were still 4.4% and 3.9% higher, with average increases in thermal time use efficiency by 23% and radiation use efficiency by 24%, which resulted in significantly higher nutrients accumulation (by 6.7%−19.7% for nitrogen and 4.1%−42.0% for phosphorous), grain yield (by 9.5%−186.4%) and yield stability (by 38.1%). These improvements were particularly pronounced in normal and dry years (2015, 2016 and 2017). No significant difference existed in maize's capacity of absorbing water and nutrients and maize productivity between SM and RP under sufficient precipitation supply (2018 and 2019). The average net profit was highest under RP, especially in dry and normal years, while SM could achieve comparable net profit to RP in wet years. Overall, RP was preferable for rainfed maize production in semi-humid drought-prone regions in any precipitation year, while SM can be an alternative mulching practice in wet years. These results can improve our understanding of how RP and SM enhance rainfed maize productivity by improving resources capture and use efficiency. ● Mulching practices effects on maize yield stability and resources use efficiency were explored. ● Ridge-furrow mulching increased thermal time use efficiency and radiation use efficiency. ● Ridge-furrow mulching obtained the highest grain yield, yield stability and net profit. ● No significant differences existed between ridge-furrow and straw mulching in wet years. ● Ridge-furrow mulching was more preferable for maize production in any precipitation year. [ABSTRACT FROM AUTHOR]

The ridge-furrow plastic mulching system has been reported to increase crop yield and water-nitrogen use efficiency in semi-arid and semi-humid regions, but the effects of plant density, nitrogen (N) rate and supplemental irrigation on chlorophyll, photosynthesis, root growth and seed yield of soybean under ridge-furrow plastic mulching are poorly understood. A two-year field experiment (2019 and 2020) was conducted on soybean in a split-split plot design, with two plant densities (D 16 : 160,000 plants ha−1; D 32 : 320,000 plants ha−1) as main plots, two N rates (N 30 : 30 kg N ha−1; N 60 : 60 kg N ha−1) as sub plots, and two irrigation levels (W 0 : rainfed; W 30 : supplemental irrigation of 30 mm at the flowering-podding stage) as sub-sub plots. The results showed that plant density, N rate and supplemental irrigation had significant effects on leaf chlorophyll content, chlorophyll fluorescence parameters, photosynthesis, aboveground/root growth and seed yield. Increasing plant density enhanced leaf area index (LAI) by 31.9% and aboveground biomass (AGB) by 59.4%, seed yield by 27.4%, water use efficiency of seed yield (WUE s) by 27.9% and nitrogen partial factor productivity (NPFP) by 26.6%. Increasing N rate increased leaf chlorophyll content by 11.9% and photosynthetic rate by 5.5%, thereby increasing LAI by 11.5%, AGB by 10.3%, seed yield by 8.9% and WUE s by 8.2%. Supplemental irrigation increased chlorophyll content by 7.6% and photosynthetic rate by 3.7%, thereby increasing LAI by 4.7%, AGB by 11.0%, seed yield by 4.7% and NPFP by 4.0%, while supplemental irrigation only increased WUE s under D 32. Compared with D 16 N 30 W 0 , D 32 N 60 W 30 enhanced seed yield by 44.0% and WUE s by 37.0%, but reduced NPFP by 28.8%. Compared with D 32 N 30 W 30 , D 32 N 60 W 30 increased both seed yield and WUE s by 8.5%, but it reduced NPFP by 45.5% with 100% higher N input. LAI, AGB, WUE s , NPFP and some leaf physiological (EXC, Chl a /Chl b , EWT leaf and L s) and root (TRLD, TRVD and TRSD) indexes were closely related to soybean yield. This study provides a better understanding how plant density, N rate and supplemental irrigation improved soybean productivity and water-nitrogen use efficiency by regulating chlorophyll, photosynthesis and aboveground/root growth. ● Plant density, nitrogen rate and supplemental irrigation effects on soybean were explored. ● They significantly affected chlorophyll, photosynthesis, root growth and seed yield. ● D 32 N 60 W 30 enhanced seed yield by 44.0% and WUE s by 37.0%, but reduced NPFP by 28.8% than D 16 N 30 W 0. ● D 32 N 60 W 30 increased seed yield and WUE s by only 8.5%, but reduced NPFP by 45.5% than D 32 N 30 W 30. [ABSTRACT FROM AUTHOR]