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Inappropriate spatial distribution of canopy and roots limits further improvements to the grain yield of maize with increased planting density. We explored an integrated management practice called strip deep rotary with staggered planting (SRS) which includes comprehensive technology for both canopy layers and topsoil. Here, field experiments were conducted under two maize cropping systems (spring maize and summer maize) to evaluate the effect of SRS on the spatial distribution of the canopy and roots for maize under high planting density (90,000 plants ha−1) and to determine the physiological factors involved in yield formation. Compared with conventional management practices (no-tillage with single planting, NTS), SRS decreased the LAI of the middle to top layers while improving the light distribution of the middle and lower layers by 72.99% and 84.78%, respectively. Meanwhile, SRS increased the root dry weight density and root sap bleeding by 51.26% and 21.77%, respectively, due to the reduction in soil bulk density by an average of 5.08% in the 0–40 cm soil layer. SRS improved the SPAD in the ear and lower leaves and maximized the LAD, which was conducive to dry matter accumulation (DMA), increasing it by 14.02–24.16% compared to that of NTS. As a result, SRS increased maize grain yield by 6.71–25.44%. These results suggest that strip deep rotary combined with staggered planting noticeably optimized the distribution of light in the canopy and reduced the soil bulk density to promote root vitality and growth, to maintain canopy longevity, and to promote the accumulation of dry matter, which eventually increased the grain yield of the maize under high planting density conditions. Therefore, SRS can be considered a better choice for the sustainable high yield of maize under high-density planting conditions in the NCP and similar areas throughout the world. [ABSTRACT FROM AUTHOR]

Reasonable canopy structure and leaf physiological characteristics are considered as important factors for improving canopy nitrogen (N) distribution by matching the available light resources and thus increasing the grain yield of maize (Zea mays L.). However, the determinants of different maize varieties in light–N matching and grain yields with specific canopy structures and leaf physiological characteristics, as well as the response to the N application rate, remain poorly understood. In this study, we analyzed the relationships between different canopy structures and the enzyme activity and light utilization of spring maize in the field. Two maize varieties (XY335 and ZD958) with different canopy structures were used as the experimental material in a 2-year field experiment from 2014 to 2015, grown under different N inputs of 0, 100, 200, and 300 kg N ha−1 (N0, N1, N2, and N3) at a planting density of 90,000 plants ha−1 in Jilin Province on the Northeast China Plain. The results show that XY335 combined with N3 had a greater leaf angle, upper internode length and number, and upper leaf area index of the upper layer compared with ZD958. Higher N assimilatory enzyme (glutamine synthase (GS), glutamate synthase (GOGAT), and nitrate reductase (NR)) activities in the upper and middle leaves were observed in XY335 compared to ZD958. Furthermore, the light interception and light utilization efficiency of the upper leaves of XY335 increased, especially at higher N application rates, which significantly affected the N translocation post-silking and its distribution in different populations. As a result, the photosynthetic N use efficiency (PNUE) values of the upper leaves (10.4%) and middle leaves (5.2%) of XY335 were higher than those of ZD958, coordinating the canopy light and N distributions and being positively correlated with the maize grain yield. This suggested that the superior canopy structure of the upper layer and N assimilatory enzymes of the upper and middle leaves of this maize variety significantly increased the light interception of the canopy, while the synchronization of light and the N of the upper and middle leaves increased the light and N utilization efficiency of maize, which ultimately increased the grain yield at a high plant density. [ABSTRACT FROM AUTHOR]

Spring wheat–summer maize (SWSM) annual crop systems were formed to satisfy the maize grain mechanized harvest thermal requirement in the thermal–resource–limited region of the North China Plain. However, the nitrogen (N) application rate effect on SWSM annual yield formation, N accumulation and utilization were barely evaluated. Two–year field experiments were conducted to evaluate the effects of the N application rate on the annual yield of SWSM, observe N accumulation and utilization, and identify the optimized N application. The experiments were conducted under 5 N levels of 0 (N0), 180 (N180), 240 (N240), 300 (N300), and 360 (N360) kg ha−1. The results showed that spring wheat, summer maize and annual cereal yield under the N240 and N480 treatments obtained the highest grain yield (GY) of 5038, 1282 and 16,320 kg ha−1, respectively, and the optimal N application rate was estimated using a linear–plateau model to be 231–307, 222–337 and 463–571 kg ha−1 with maximum GY of 4654–5317, 11,727–12,003 and 16,349–16,658 kg ha−1, respectively. With the increase in the N application rate, the dry matter accumulation (DM) were significantly increased by 16.9–173.5% for spring wheat and 11.1≈–76.8% for summer maize, respectively; and the annual cereal DM was 15.1–179.7% greater than that with N0 treatment, respectively. Spring wheat, summer maize and the annual cereal total N accumulation (TN) under N360 and N720 treatments were significantly increased by 5.4–19.1%, 16.6–32.3% and 11.5–26.2%, respectively, compared to the other treatments; however, N use efficiency for biomass and grain production (NUEbms and NUEg) were decreased significantly by 10.9–13.6% and 8.9–20.7%, 6.8–13.8% and 12.2–15.6%, and 5.5–11.7% and 10.0–16.0%, respectively. Meanwhile, the N partial factor productivity (PFPN), N agronomy use efficiency (ANUE), N recovery efficiency (NRE) and N uptake efficiency (NEupk) under the N240 treatment for spring wheat and summer maize obtained high levels of 20.99 and 47.01 kg−1, 9.27 and 16.35 kg−1, 32.53% and 32.44%, and 0.85 and 0.72 kg−1, respectively. Correlation analysis showed that the N application rate, TN and NEupk played significantly positive roles on GY, spring wheat spilke grain number, summer maize ear grain number and 1000–grain weight, DM LAImax and SPADmax, while NUEbms, NUEg, PFPN and ANUE always played negative effects. These results demonstrate that spring wheat, summer maize and annual cereal obtained the highest GY being 4654–5317, 11,727–12,003 and 16,349–16,658 kg ha−1 with the optimal N application rate 231–307, 222–337 and 463–571 kg ha−1, respectively, which provide N application guidance to farmer for spring wheat–summer maize crop systems to achieve annual mechanical harvesting in the thermal–resource–limited region of the North China Plain. [ABSTRACT FROM AUTHOR]

In order to study the effect of green manure return for stabilized spring maize (Zea mays L.) grain yield (GY) we reduced nitrogen fertilizer input by regulation and examined effects on soil nutrients, enzyme activity, and fungal communities. This two-year field experiment was conducted in the North China Plain. The field experiment was undertaken with a split-plot design; the primary plots were winter fallow (WF) and green manure (GM), and the split-plots were five N application rates of 0 (N0), 189 (N189), 216 (N216), 243 (N243), and 270 (N270) kg ha−1. The results showed that, spring maize GY under GM treatments (GYGM) were significantly increased by 5.38–11.68% more than WF treatment (GYWF), and GYWF and GYGM significantly increased by 35.9–91.5% and 80.1–135.5% across all N treatments. By linear-platform model analysis, spring maize under GM treatments obtained higher GY, reaching 1270.5–14,312.2 kg ha−1 with optimized N application rate at 238–265 kg ha−1, which resulted in a GY higher than WF (11,820.0 and 13,654.2 kg ha−1) and N reduced 11.2% (238 vs. 268 kg ha−1). GM treatment significantly increased soil organic carbon by 3.90–12.23% more than WF over all N application rates, and total nitrogen and available nitrogen were significantly increased by 3.79–15.76% and 4.87–17.29%, with total phosphorus and available phosphorus for GM higher than WF by 6.1–13.6% and 9.6–5.3%, respectively. However, there were lesser effects of GM on total potassium and available potassium. Compared to WF, soil catalase, sucrose, urease, and alkaline phosphatase activity were significantly increased by 6.2–16.4%, 5.8–48.1%, 3.3–21.5% and 11.5–82.3%, respectively, over all N application rates under GM over two years. GM increased Zygomycota and Basidiomycota relative abundances significantly, and reduced Thielavia, unclassified fungi, and Podospora relative abundances by 35.35%, 52.92% and 52.77% more than WF treatment, respectively. In summary, due to the GM return into fields, increased soil nutrients were available, which were positively affected by soil enzyme activity and fungal communities, and reduced nutrient requirements, and so the farmers could obtain a spring maize grain yield higher than 14,000 kg ha−1 with a reduced 11.2% N application rate from 268 kg ha−1 to 238 kg ha−1 by sowing winter green manure for a long time period in the North China Plain. [ABSTRACT FROM AUTHOR]

In order to evaluate the effects of climatic conditions on maize grain yield (GY), kernel weight (KW), and kernel filling and identify the optimal climatic factors for GY and KW, 2-year field experiments in three seasons, i.e., spring (SPM), summer (SUM), and autumn (AUM), on maize were conducted in Central China. The results showed that SUM had more growing degree days (GDDs) than SPM and AUM due to the higher mean temperature (MT), and also resulted in higher temperature stress (killing degree days (KDDs)) in maize growth duration. Meanwhile, after silking, SPM and SUM had more GDDs and KDDs than AUM because of the higher MT, and the accumulated solar radiation (Ra) for SUM was significantly higher than for SPM and AUM. The GY of SPM was significantly higher than that of SUM and AUM, while SUM's GY was always the lowest, because the GDDGD, MTGD, and KDDGD played significantly negative roles on GY. The final KW for SUM was always the lowest, with GDD, MT, KDD, and Ra causing significantly negative effects, and M△T and precipitation having significant positive effects, resulting in a lower kernel filling rate during the linear kernel filling period (KFRlkf) and a lower GDD at the maximum kernel filling rate (GDDKFRmax). Maize KFRlkf has significant negative linear dependences on GDD, MT, and Ra. In summary, because of the higher MT, KDD, and GDD during maize growth and kernel filling duration negatively affecting the maize kernel filling rate, the GY and KW for SPM were the highest, and for SUM, they were the lowest; therefore, farmers should plant SPM first and then AUM in Central China. [ABSTRACT FROM AUTHOR]

Subsoiling is an important management practice for improving maize yield, especially for maize planted at high plant density. However, the affected physiological processes have yet to be specifically identified. In this study, field experiments with two soil tillage (CK: no-tillage, SS: subsoiling) and three planting densities (low: 45000 plants ha−1, medium: 67500plants ha−1, and high: 90000 plants ha−1) were conducted from 2010 to 2012 at Xinxiang, Henan province. Yield, canopy function, and root system were investigated to determine the associated physiological processes for improving maize production affected by soil tillage and plant density. Subsoiling significantly increased the grain yield of the low-, medium-, and high-planting densities by 6.21%, 8.92%, and 10.09%, respectively. Yield increase in the SS plots was mainly attributed to greater post-anthesis DMA and improved grain filling compared to CK plots. Greater green leaf area, leaf net photosynthetic rate, FV/Fm and ΦPSII in the SS plots were mainly contributed to enhanced dry matter production post-anthesis. This is mainly because subsoiling increased density of root dry weight in deep soil and root bleeding sap amount due to decreased the bulk density of the 0–30 cm soil profile layer. Density of root dry weight at 10–50 cm depth with SS increased by 40.68%, 32.17%, and 20.14% at low, medium, and high planting densities compared to CK, respectively, while the root bleeding sap amount increased by 17.41%, 15.82%, and 20.91%. These results indicate that subsoiling could change the root distribution and improve soil layer environment for root growth, thus maintaining a higher canopy photosynthetic capacity post-anthesis and in turn promoting DMA and yield, particularly at higher planting densities. [ABSTRACT FROM AUTHOR]