To determine the optimal planting density under wide-width sowing condition, we investigated the effects of different planting densities on photosynthetic characteristics of flag leaves, senescence characteristics of flag lea-ves and roots, grain yield, and water use efficiency under four planting density levels, 90×104 plants·hm-2 (D1), 180×104 plants·hm-2 (D2), 270×104 plants·hm-2 (D3) and 360×104 plants·hm-2 (D4), in field condition set in Yanzhou, Shandong during the growing season of 2018-2019 and 2019-2020. The results showed that compared with D1 and D4 treatments, D2 treatment significantly improved photosynthetic characteristics of wheat flag leaves during grain filling, increased the activity of superoxide dismutase (SOD) and soluble protein content, reduced the malondialdehyde (MDA) content, and delayed the senescence of flag leaves and roots. Compared with other treatments, D2 treatment significantly increased root length, root surface area and root volume in 0-40 cm soil layer. Compared with D1, D3 and D4 treatments, the grain yield of D2 treatment was increased by 11.8%, 2.5%, 6.4% in 2018-2019 and 22.7%, 5.7%, 17.1% in 2019-2020, respectively. In addition, water use efficiency was increased by 9.2%, 8.8%, 14.2% in 2018-2019 and 21.1%, 6.2%, 21.5% in 2019-2020, respectively. The planting density at 180×104 plants·hm-2 improved photosynthetic characteristics of flag leaves and root morphology during filling stage, delayed plant senescence, increased grain number per spike and grain weight. Consequently, the highest grain yield and water use efficiency were obtained under D2 treatment, which was the optimal treatment under the experimental wide-width sowing condition.

为深入实施藏粮于地战略,提高小麦产量,本试验以高产小麦品种烟农1212为供试材料,研究每公顷产10 500kg(S)、9 000kg(H)和7 500 kg(M)水平麦田小麦光能利用和干物质积累转运的差异.结果表明:S麦田拔节期至成熟期群体总茎数显著高于H和M麦田,开花期叶面积指数达8.9,开花期冠层光合有效辐射截获率高达96.85％并分别比H和M麦田显著高出6.00％和11.71％,开花后光能利用率和光能转化率分别比H和M麦田显著高出7.85％、17.65％和4.25％、10.28％.S麦田越冬期至成熟期干物质积累量显著高于其他麦田,开花后同化物在籽粒中的分配量达8 163.03 kg/hm2,分别比H和M麦田显著高出38.15％和102.51％;S麦田单位面积穗数、穗粒数和千粒重分别达689.95万/hm2、39.79粒和48.83 g,单位面积穗数、千粒重分别较H和M麦田显著提高12.67％、27.14％和6.73％、10.68％,S麦田产量达11 280.54 kg/hm2,较H和M麦田分别显著提高19.64％和51.68％.在10 500 kg/hm2产量水平麦田,小麦光能利用率显著提高,促进了开花后干物质的积累,通过提高穗数和千粒重获得高产.

Border irrigation is still the main irrigation method in the Huang-Huai-Hai Plain of China (HPC), and the suitable irrigation border length for water saving and high yield under traditional irrigation is still unclear. Therefore, a 2-year traditional border irrigation experiment (2017–2019) was conducted on the HPC. Four border lengths were tested: 20 m (L20), 30 m (L30), 40 m (L40), and 50 m (L50). These treatments were given supplementary irrigation at jointing and anthesis. An exclusively rainfed condition formed the control treatment. Compared with other treatments, the activities of superoxide dismutase antioxidant and sucrose phosphate synthetase, and the contents of sucrose and soluble proteins after anthesis were higher in the L40 and L50 treatments, while the content of malondialdehyde content was lower. Therefore, the L40 treatment effectively delayed the decrease in the soil plant analysis development (SPAD) value and chlorophyll fluorescence characteristics, promoted grain filling, and achieved the highest thousand-grain weight. Compared with the L40 treatment, the grain yields of the L20 and L30 treatment were significantly reduced, while the water productivity of the L50 treatment was significantly reduced. These findings suggest that 40 m was the optimal border length for both high yield and water saving in this experiment. This study provides a simple and low-cost water-saving irrigation method for winter wheat in the HPC under traditional irrigation, which can help alleviate the pressure of agricultural water use.

The ridge–furrow planting pattern is an effective strategy to improve grain yield, and changes in the ridge and furrow microenvironments affect wheat yield. However, the mechanism by which wheat yields are increased at different ridge–furrow ratios is unclear. In this study, four planting modes, namely the traditional planting mode (M1) and ridge–furrow ratios of 50:50 cm (M2), 75:50 cm (M3), and 100:50 cm (M4), were established for wheat under field conditions from 2021 to 2023; the effects of different treatments on light energy utilization, dry matter accumulation and transport, and grain yield were studied. The findings demonstrated that the M3 treatment exhibited the highest enhancements in parameters such as leaf area index (LAI), canopy photosynthetically effective radiation interception rate, relative chlorophyll content (SPAD) index, and net photosynthetic rate. Moreover, the M3 treatment displayed superior grain filling compared to other treatments. The post-anthesis assimilate accumulation in the M3 treatment was 11.93%, 4.69%, and 13.13% higher than that of M1, M2, and M4 treatments, respectively, and the grain yield in M3 increased by 7.70–9.56%, 3.13–4.91%, and 8.69–10.90% compared with those in M1, M2, and M4 in the two growing seasons, respectively. In summary, under the conditions of this study, the M3 treatment led to higher LAI and SPAD values in flag leaves post-anthesis compared to the other treatments. Moreover, M3 optimized canopy structure, led to the highest canopy interception rate, and increased photosynthetic rates per individual plant. Consequently, there was a significant increase in post-anthesis dry matter accumulation, resulting in the highest grain yield achieved among the treatments.

Scholars have proposed the practice of split nitrogen fertilizer application (SNFA), which has proven to be an effective approach for enhancing nitrogen use efficiency. However, the combined effects of SNFA on wheat plant nitrogen use efficiency, ammonia (NH3) emission flux, as well as the rates of nitrification and denitrification in different ecosystems remain unclear. Meanwhile, few studies have sought to understand the effects of the split nitrogen fertilizer method under water-saving irrigation technology conditions on nitrogen loss. The current study assessed soil NH3 volatilization, nitrification, and denitrification intensities, as well as the abundance of nitrogen cycle-related functional genes following application of different treatments. Specifically, we applied a nitrogen rate of 240 kg⋅ha–1, and the following fertilizer ratios of the percent base to that of topdressing under water-saving irrigation: N1 (basal/dressing, 100/0%), N2 (basal/dressing, 70/30%), N3 (basal/dressing, 50/50%), N4 (basal/dressing, 30/70%), and N5 (basal/dressing, 0/100%). N3 treatment significantly reduced NH3 volatilization, nitrification, and denitrification intensities, primarily owing to the reduced reaction substrate concentration (NO3– and NH4+) and abundance of functional genes involved in the nitrogen cycle (amoA-AOB, nirK, and nirS) within the wheat-land soil. 15N tracer studies further demonstrated that N3 treatments significantly increased the grain nitrogen accumulation by 9.50–28.27% compared with that under other treatments. This increase was primarily due to an increase in the amount of nitrogen absorbed by wheat from soil and fertilizers, which was caused by an enhancement in total nitrogen uptake (7.2–21.81%). Overall, N3 treatment (basal/dressing, 50/50%) was found to effectively reduce nitrogen loss through NH3 volatilization, nitrification and denitrification while improving nitrogen uptake by wheat. Thus, its application will serve to further maximize the yield and provide a fertilization practice that will facilitate cleaner wheat production in the North China Plain.

We aimed to optimize field border length in the Huang-Huai-Hai Plain of China (HPC) to reduce soil inorganic nitrogen residues and increase nitrogen absorption and utilization by wheat plants using a traditional border irrigation system. In a two-year experiment (2017–2019) conducted in the HPC, four border lengths were tested: 20 m (L20), 30 m (L30), 40 m (L40), and 50 m (L50). Supplementary irrigation was implemented during jointing and anthesis stages, and control fields received treatment without irrigation. The results showed that, compared with irrigation of other border lengths, L40 irrigation significantly increased nitrogen transport in stems and leaves. In addition, L40 irrigation had the highest rate of grain nitrogen accumulation after anthesis. The risk of nitrate leaching to deep layers increased with increasing border length; however, L40 irrigation improved the plants’ capacity to absorb soil nitrogen, and the soil inorganic nitrogen residue was significantly lower than that with irrigation of other border lengths. Therefore, the grain yield and nitrogen fertilizer utilization under L40 irrigation were significantly higher than those under irrigation of other border lengths, and L40 was considered as the best border irrigation length.

Clarifying factors that underpinning the variation in wheat yield components between high and middle soil fertility fields is critical to increase grain production and narrow yield gap for smallholder farming systems in the Huang–Huai–Hai Plain (3HP), which characterized by a large variation in soil fertility. Two-year field experiments were conducted to investigate wheat tillering, leaf photosynthesis, and grain filling characteristics in different soil fertility fields: high soil fertility field (HF) and middle soil fertility field (MF). Results showed that the spike formation rate in HF was 12.7%–13.0% higher than that in MF, leading to an 18.0%–19.8% increase in spike number. In addition, HF improved canopy light interception and leaf photosynthesis characteristics after anthesis and delayed leaf senescence, contributing to the increase in both the active grain filling period and grain filling rate. This resulted in a higher 1,000 grain weight in HF, which was 8.2%–8.3% higher than that in MF. Compared to MF, HF obtained higher yields at 9,840 kg ha−1 in 2017/18 and 11,462 kg ha−1 in 2018/19, respectively. In summary, higher spike number and 1,000-grain weight, which were mediated by spike-formation rate, maximization of light interception and improved leaf photosynthesis. These results would have important implications for narrowing yield gap between MF and HF in the 3HP.

研究高产与中产麦田小麦产量、光能和氮素利用效率的差异，为缩小产量和资源利用率差，实现小麦高产高效生产提供理论依据。选取高产田和中产田2块麦田，常年小麦产量水平分别为9 000,7 500 kg/hm~2。以小麦品种“烟农1212”为供试材料，分析不同产量水平麦田光能利用和氮素利用的差异。结果表明，高产田植株拔节期、开花期和成熟期氮素积累量较中产田提高6.65%～11.25%,开花前氮素向籽粒中的转运量较中产田提高11.60 kg/hm~2,开花后氮素同化量较中产田提高21.99 kg/hm~2。开花后14～28天旗叶氮代谢酶活性均表现为高产田显著高于中产田。高产田土壤氮素表观盈亏量较中产田减少48.61%。高产田开花期和开花后7～28天叶面积指数和旗叶SPAD值较中产田分别提高6.89%～34.56%和8.45%～27.32%;开花期和开花后7～28天高产田冠层光能有效辐射截获率和截获量较中产田提高3.92%～7.70%和3.97%～7.85%。高产田籽粒产量较中产田提高26.71%,光能利用率和氮素利用率分别提高17.39%和19.50%。综上所述，高产田小麦开花后冠层光能有效辐射截获率和营养器官贮存氮素向籽粒的转运量高，提高小麦成熟期籽粒中氮素的积累量，进而提高产量、光能利用率和氮素利用率，同时减少土壤氮素表观盈亏量，减少氮素损失。

Selecting high-yielding wheat varieties for cultivation can effectively increase water use efficiency (WUE) in the Huang–Huai–Hai Plain, where is threatened by increasing water shortages. To further identify the difference in water use and its relationship with root morphology and senescence characteristics, wheat varieties with different yield potentials—Yannong 1212 (YN), Jimai 22 (JM), and Liangxing 99 (LX)—were studied in a high-yielding wheat field. The water consumption percentage (CP) in YN decreased from planting to anthesis; however, crop evapotranspiration and CP increased from anthesis to maturity compared with JM and LX. In YN, a higher soil water consumption from anthesis to maturity in the 0–100 cm soil layer was partly attributed to the greater root weight density in the 20–60 cm soil layer. In topsoil (0–40 cm), root length density, root surface area density, and root diameter at 20 days after anthesis, root superoxide dismutase activity, and root triphenyl tetrazolium chloride reduction activity during mid grain filling stage were higher in YN than in JM and LX. YN had the highest grain yields of 9,840 and 11,462 kg ha–1 and increased grain yield and WUE by 12.0 and 8.4%, respectively, as compared with JM, and by 30.3 and 21.3%, respectively, as compared with LX. Ensuring more soil water extraction post-anthesis by increasing roots in the 20–60 cm soil profile, improving root morphology traits, and alleviating root senescence in the topsoil during mid-grain filling stage will assist in selecting wheat varieties with high yield and WUE.

Background Exploring suitable split nitrogen management is essential for winter wheat production in the Huang-Huai-Hai Plain of China (HPC) under water-saving irrigation conditions, which can increase grain and protein yields by improving nitrogen translocation, metabolic enzyme activity and grain nitrogen accumulation. Methods Therefore, a 2-year field experiment was conducted to investigate these effects in HPC. Nitrogen fertilizer was applied at a constant total rate (240 kg/ha), split between the sowing and at winter wheat jointing growth stage in varying ratios, N1 (0% basal and 100% dressing fertilizer), N2 (30% basal and 70% dressing fertilizer), N3 (50% basal and 50% dressing fertilizer), N4 (70% basal and 30% dressing fertilizer), and N5 (100% basal and 0% dressing fertilizer). Results We found that the N3 treatment significantly increased nitrogen accumulation post-anthesis and nitrogen translocation to grains. In addition, this treatment significantly increased flag leaf free amino acid levels, and nitrate reductase and glutamine synthetase activities, as well as the accumulation rate, active accumulation period, and accumulation of 1000-grain nitrogen. These factors all contributed to high grain nitrogen accumulation. Finally, grain yield increase due to N3 ranging from 5.3% to 15.4% and protein yield from 13.7% to 31.6%. The grain and protein yields were significantly and positively correlated with nitrogen transport parameters, nitrogen metabolic enzyme activity levels, grain nitrogen filling parameters. Conclusions Therefore, the use of split nitrogen fertilizer application at a ratio of 50%:50% basal-topdressing is recommended for supporting high grain protein levels and strong nitrogen translocation, in pursuit of high-quality grain yield.

为明确不同土壤肥力下小麦干物质生产和产量的差异,于2019-2020年小麦生长季,选择了产量潜力分别为10 500 kg·hm-2和9 000 kg·hm-2的超高产土壤肥力和高产土壤肥力两种麦田,以济麦22为材料,比较分析了不同土壤肥力麦田小麦的群体动态、干物质生产、籽粒灌浆特性、穗部特征和产量构成的差异.结果表明,与高产土壤肥力相比,超高产土壤肥力增加了小麦拔节至成熟期的干物质积累量及成熟期干物质在籽粒中的分配量,促进了小麦开花前营养器官储存同化物在开花后向籽粒的转运量和开花后的光合物质同化量,提高了收获指数;超高产土壤肥力使籽粒在灌浆中后期维持较高的灌浆速率,延长了活跃灌浆期,提高了粒重.超高产土壤肥力通过增加单位面积的穗数和千粒重,实现小麦高产.

Efficient nitrogen fertilizer management is critical for increasing winter wheat production and ensuring the longterm protection of the agricultural environment. Determining the features of soil greenhouse gas (GHG) emissions and the driving factors of split nitrogen fertilization is important for optimizing cropland nitrogen management. To date, few studies have comprehensively evaluated the trade-offs between reducing greenhouse gas intensity and improving grain yield in winter wheat cropping systems using split nitrogen applications under water-saving irrigation conditions. Here, a two year field trial using split nitrogen fertilization under water saving irrigation was done to determine the impacts of split nitrogen fertilizer on soil greenhouse gas intensity and wheat yield. The soil GHG fluxes, inorganic nitrogen, water moisture, and grain yield were measured for five nitrogen treatments. The nitrogen application rate was 240 kg ha(-1), and five fertilizer ratios of base to topdressing of N1 (100 % basal and 0% dressing fertilizer), N2 (70 % basal and 30 % dressing fertilizer), N3 (50 % basal and 50 % dressing fertilizer), N-4 (30 % basal and 70 % dressing fertilizer), and N5 (0% basal and 100 % dressing fertilizer) were applied. Our results showed that the split nitrogen fertilization strategy had a significant influence on the GHG emissions. And our findings suggested that soil inorganic nitrogen and water moisture was the key variable affecting the soil GHG emissions in the winter wheat cropping system. Compared with the other treatments, the N-3 treatment changed the soil inorganic nitrogen and water moisture more effectively with regards to decreased the soil N2O, CH4 and CO2 cumulative emissions, as well as decreased global warming potential and greenhouse gas intensity. The N-15 tracer experiments showed that N3 significantly increased the absorption and utilization rate of nitrogen fertilizer and soil nitrogen by winter wheat. The average grain yield and nitrogen use efficiency with the N3 treatment increased by 5.29 similar to 15.34 % and 5.25 similar to 13.14 %, compared with other treatments, respectively. If the basal/topdressing fertilization rate is 50 %:50 %, the split nitrogen fertilizer can maintain a higher grain yield and reduce GHG emissions.

为明确山东省高产麦区高产节肥高效的施氮量,以高产小麦品种济麦22和烟农1212为材料,在大田试验测墒补灌条件下,设置0(N0)、180(N1)、210(N2)、240 kg·hm-2(N3)四个施氮量水平,研究施氮量对小麦旗叶光合特性、干物质积累分配和籽粒产量的影响.结果表明,适量施氮可显著提高灌浆中后期旗叶的叶绿素相对含量、净光合速率、蒸腾效率和气孔导度,增加拔节期至成熟期小麦的干物质积累量,提高干物质在籽粒中的分配量及其对籽粒产量的贡献率;与不施氮肥处理相比,施氮180～240 kg·hm-2时,济麦22增产10.1％～28.2％,烟农1212增产27.1％～42.8％.在同一施氮处理下,开花期至成熟期,烟农1212的干物质积累量比济麦22高12.77％～19.92％;花后14～28 d,烟农1212的旗叶净光合速率比济麦22高8.61％～24.11％;灌浆期间,烟农1212花前营养器官贮藏干物质向籽粒的转运量比济麦22高6.10％～11.68％,花后光合同化物积累量比济麦22高12.63％～22.00％,籽粒产量增加12.73％～19.46％.说明适量施氮有利于灌浆中后期小麦旗叶保持较高的光合性能,促进花后光合同化物的积累和向籽粒的分配,发挥品种的高产潜力.当施氮量为210 kg·hm-2时,济麦22和烟农1212的籽粒产量、氮肥农学效率和氮肥偏生产力均最高,是该试验条件下的最优施氮量.

With water resources becoming scarcer and a growing demand for increased food supplies, there is an urgent need to maximize the efficiency of irrigation systems. We aimed to find a suitable border length to reduce the quantity of irrigation water through a traditional border irrigation system and, thus, alleviate groundwater depletion in Huang-Huai-Hai Plain (3HP). A 2-year experiment (2017–2019) was conducted in 3HP, which three border lengths were tested: 15 m (L15), 25 m (L25), and 35 m (L35); supplementary irrigation was implemented during jointing and anthesis, inflow cutoff was set at 90%, and set a control treatment without irrigation (CK). The results showed that L25 significantly improved soil water distribution after irrigation, and increased soil water consumption compared with L15 and L35. The the dry matter accumulation post-anthesis was also higher in L25 than in the other treatments, as well as the WUE. The correlation analysis of soil water content after irrigation with yield confirmed that L25 was more conducive to high grain yield. Hence, under these test conditions, the irrigation field treatments with a border length of 25 m were considered the most efficient, given that these allow the reduction of the amount of water necessary for irrigation without compromising grain yield of winter wheat.

[目的]探究开花期土壤水分含量对小麦植株氮素积累转移、土壤硝态氮含量、小麦产量及氮素利用率的影响,为小麦氮素高效利用及节水高产栽培提供理论依据.[方法]于2018—2019和2019—2020年两个小麦生长季,在大田条件下,供试品种为济麦22,在开花期设置3个水分处理:不灌水(W0)、将0—40 cm土层土壤相对含水量补灌至70％(W1)和85％(W2).测定了小麦开花期和成熟期氮素的积累和转运、小麦产量及氮素利用率,并对小麦成熟期0—200 cm土层土壤硝态氮含量进行分析.[结果]1)W1处理中,两个小麦生长季开花期营养器官贮存氮素转移量比W0和W2处理平均提高11.63％和7.27％,氮素转移率分别增加9.49％和6.11％;成熟期籽粒氮素分配量平均提高22.5％和12.9％,但叶片和穗轴+颖壳中的氮素分配量显著低于W0和W2处理,因而提高了氮素收获指数.2)补灌至70％(W1)处理降低了60—120 cm土层土壤硝态氮含量,小麦氮素吸收量比W0和W2处理平均提高11.4％和6.5％,土壤氮素表观盈余量平均降低51.0％和40.9％,W1处理减少硝态氮向深层土壤淋溶的风险,降低了0—200 cm土层土壤中无机氮的残留量和土壤氮素表观盈余量,有利于小麦根系对土壤氮素的吸收利用.3)W1处理的小麦千粒重比W0和W2处理平均增加11.0％和5.4％,籽粒产量提高25.9％和11.8％,水分利用效率平均提高17.0％和12.7％,氮素吸收效率提高了11.4％和6.5％,氮素利用效率增加了13.0％和4.9％.[结论]在小麦开花期,将0—40 cm土层土壤相对含水量补灌至70％,可以显著提高小麦灌浆中后期营养器官贮存氮素向籽粒的转移量和转移率,提高小麦成熟期籽粒中氮素的积累量和分配率,进而提高了产量、氮素收获指数、氮素利用率和水分利用效率,同时降低了60—120 cm土层土壤硝态氮含量,因而减少了环境风险.灌溉过量导致硝态氮过多向下移动,影响根系吸收,水分不足则降低氮素向籽粒的运转.

Evaluating the effects of nitrogen (N) on photosynthesis characteristics and photoassimilate partitioning via vascular bundles (VB) under water-saving irrigation is crucial to maximum grain yield of environment-friendly wheat production in the North China Plain (NCP). Field experiments were conducted with four N application rates 0 (N 0 ), 180 (N 180 ), 240 (N 240 ), and 300 (N 300 ) kg N ha −1 under 70% and 65% relative soil water content (RSWC) at jointing and anthesis, respectively. Results showed that, compared with N 0 , N 180 significantly improved the photosynthetic parameters and chlorophyll fluorescence of flag leaf after anthesis. N application improved the anatomical parameters both in the flag leaf and the stem. Total transverse area of VB in the flag leaf and in the stem internode below the ear under N 180 was 17.95–23.70% and 37.91–43.90% larger than those of N 0 , respectively, due to the increased numbers and transverse area of VB. Furthermore, N 180 had higher dry matter assimilation after anthesis (DMA) and its contribution to the grain. N 180 increased grain yield by 14.23–23.24% compared with N 0 , and N supply exceeding 180 kg N ha −1 did not further increase yield. Moreover positively correlations were showed among photosynthesis characteristics after anthesis, total transverse area of VB in the flag leaf and in the stem internode below the ear, DMA and grain yield. In summary, the recommended N application rate was 180 kg N ha −1 under RSWC-based supplemental irrigation that can produce grain yield over 7500 kg ha −1 for at least 2 years in the NCP.

为探明不同产量潜力小麦品种氮素积累与转运的规律,于2019-2020年度小麦生长季,以3个产量潜力不同的小麦品种烟农1212、济麦22和良星99为供试材料,分析了 3个小麦品种氮素积累、转运和籽粒产量的差异.结果表明,烟农1212在小麦拔节至开花期和开花至成熟期植株氮素积累速率显著高于济麦22和良星99,开花期和成熟期植株氮素积累量也显著高于其他两个品种;在开花后0～7 d,籽粒氮素积累量和积累速率在3个品种间无显著差异,花后7～14 d,两个指标在烟农1212和济麦22间无显著差异,但均显著高于良星99,花后21～35 d,烟农1212的籽粒氮素积累量和积累速率显著高于其他两个品种.烟农1212花前氮素转运量和开花后氮素积累量均最高.相关分析表明,籽粒产量与开花期和成熟期的氮素积累量呈极显著正相关,烟农1212较济麦22和良星99分别增产9.32％和14.10％,获得最高的氮素吸收效率、氮素收获指数和氮肥偏生产力.在本试验条件下,烟农1212是开花期和成熟期氮素积累量、花前氮素转运量和产量最高的小麦品种.

Sustainable agriculture in the Huang–Huai–Hai Plain of China is threatened by subsoil compaction and the decline of winter wheat productivity induced by inappropriate tillage regimes. We investigated the effects of optimizing the tillage regime on grain filling and its relationship with flag leaf senescence post-anthesis in winter wheat. Four treatments were compared: rotary tillage, strip rotary tillage, strip rotary tillage with a 2-year subsoiling interval (STS), and conventional plowing tillage. STS produced higher chlorophyll content and leaf area indexes than other treatments, resulting in a greater photosynthetically active radiation capture ratio. The net photosynthesis rate of flag leaves from 14 to 28 days after anthesis and dry matter accumulation at maturity were higher in STS than in other treatments. Sucrose content and sucrose phosphate synthase activity of flag leaves first increased and then decreased during grain filling and were highest in STS. STS increased superoxide dismutase activity, increased soluble protein content, and reduced malondialdehyde concentrations in flag leaves after the middle grain-filling stages, resulting in reduced premature senescence. This consequence extended the active grain filling period and increased grain weight. The highest yields were observed in STS, reaching 10,451 kg ha−1 in 2014–2015 and 10,074 kg ha−1 in 2015–2016, owing to increased spike numbers and 1000-kernel weight. Overall, our study suggested that STS could substantially increase photosynthetic capacity and delay leaf senescence, thus promoting grain filling rate and increasing winter wheat yields.

Water scarcity is a great challenge for wheat production. Recently, a new supplemental irrigation (SI) regime, which considers crop requirement and soil water storage, is being widely adopted for saving water in wheat fields. However, the effects of nitrogen (N) fertilization rates on wheat under this new SI regime have been rarely assessed. A two-year field experiment was conducted using four N rates (0, 180, 210, 240 kg ha(-1)) under SI to address the research gap. Compared to the conventional flood irrigation, SI increased the total dry matter accumulation at maturity and dry matter allocation to grain in post-anthesis phase, increasing grain yield. At 210 kg N ha(-1), the higher nitrogen use efficiency (NUE) and water use efficiency (WUE) were attained under SI than under conventional flood irrigation. For different N rates, soil water consumption from 80-120 cm soil layer was higher at 210 kg N ha(-1). The flag leaf water potential, Phi PSII, and Fv/Fm at 210 kg N ha(-1) during 14-28 days after anthesis were higher which resulted in high dry matter accumulation. The WUE and grain yield were higher at N rate of 210 kg ha(-1) treatment, which also recorded higher NUE than 240 kg N ha(-1) but lower than 180 kg N ha(-1). Therefore, 210 kg N ha(-1) with SI regime can be the optimum nitrogen and water management for increasing wheat yield, WUE and NUE in semiarid regions. (C) 2020 Friends Science Publishers

Although the effect of tillage practices on crops has been well studied, the systematic effect of these practices on the yield formation process of wheat in rainfed regions is often poorly reported. Here, four tillage practices, namely, strip rotary tillage (SR), strip rotary tillage after subsoiling (SRS), rotary tillage (R) and rotary tillage after subsoiling (RS), were performed during 3 wheat-growing seasons to study the effect of tillage practices on the yield formation process and the physiological mechanism in rainfed wheat. SRS and SR reduced the tiller numbers but increased the percentage of earring tillers. SRS and SR produced the spike numbers similar to those produced by RS and R but increased the grain numbers per spike by increasing the number of grains per spikelet. SRS reduced the evapotranspiration (ET) during the early-filling stage and increased the ET and water consumption ratio during the mid- and late-filling stages. Because of increased water consumption, the flag leaf water potential by SRS was improved during the late-filling stage; photosynthetic rate and superoxide dismutase activity also improved. Accompanied by the improvement in physiological characteristics, the post-anthesis dry matter accumulation by SRS increased significantly. The average grain yield by SRS in the three growing seasons was 6.0 %, 13.4 % and 7.0 % higher than those by SR, R and RS, respectively. The yield-increasing effect of subsoiling once could last for 3 years but the growth rate on the third year decreased from 8.6 % to 3.2 % in SRS, and decreased from 6.0 %-4.2 % in RS.