A strong canopy structure is central to maximizing yield. The canopy microenvironment, which is related to crop growth and development, reflects changes in a crop’s microclimate. In this study, with the uniform sowing of winter wheat (Triticun aestivum L.), five planting densities (in 10⁴ plants·ha⁻¹: 123, 156, 204, 278, and 400) were established to examine how the planting density affected filling stage spikes, canopy structures, microenvironments, yields, and yield components. The large-spike Xindong 50 and multi-spike Sangtamu 4 varieties were used. The experiment was conducted over 263 days in the Xinjiang province, in a warm continental arid desert-type climate, with low precipitation. The study aimed to determine the optimal parameters for cultivation on limited land and improve the production potential. For both varieties, from anthesis to filling, increases in planting density were associated with a rapid reduction in the leaf area index of the lower and middle parts of the leaves. Canopy temperature and canopy CO₂ concentration also decreased, whereas relative humidity increased. The number of grains per spike and the thousand-grain weight of both varieties decreased with increased planting density. Yields were maximized at densities of 278 × 10⁴ and 156 × 10⁴ plants·ha⁻¹ for the large- and multi-spike varieties, respectively, indicating that uniform sowing improves plant uniformity, and adjusting planting density optimizes canopy structure and microenvironment. Our study provides valuable data for optimizing planting densities to ensure high yields.

In North China, row spacing is the most common planting pattern used for winter wheat. Currently, there are three sowing and tillage methods for row spacing: rotary tillage sowing with straw return (RTS), subsoil tillage sowing with straw return (DTS), and no-tillage sowing with straw return (NTS). Recently, Hao proposed a new sowing pattern called uniform broadcast sowing with straw return (BSS) which could increase winter wheat yield. In this research, a field experiment was conducted during the growing seasons in 2011–2012 and 2012–2013. The winter wheat (Triticum aestivum L.) variety Jimai 22 was sowed with the four seeding and tillage methods—RTS, DTS, NTS, and BSS—at the China Agriculture University Wuqiao experimental station in the North China Plain. After tillage sowing and determining the sowing efficiency, the effective cover ratio of the seeds was measured, and the emergence ratio was calculated after emergence. In the two growing seasons, the growth and development stages were recorded. The dry matter accumulation (DMA), the yield, and the yield components (spikes per hectare, kernels per spike, and kernel weight) were also determined. We also measured the canopy structure leaf area index (LAI) and the stand uniformity. The results showed that BSS had the lowest emergence rate and lowest plant stands when compared with the other treatments. However, BSS had the highest grain yield at 7599.0 kg·ha⁻¹ and 9763.3 kg·ha⁻¹, which was 11.55, 16.17, 20.16% and 13.01, 15.68, 21.88% higher than DTS, RTS, and NTS in the 2011/2012 and 2012/2013 growing seasons, respectively. The improved grain yield of BSS was due to the increased productive tillers per hectometer-squared, which was attributed to the higher stand uniformity. More importantly, the increased tillers per hectare and grain yield were not accompanied by a reduction in grain number per spike or grain weight. The stand uniformity could facilitate canopy construction and population architecture and result in more even sunlight distribution, increased leaf area index (LAI) and sunlight interception, and enhanced photosynthetic activity. The stand uniformity also could increase both the pre-anthesis and post-anthesis DMA and promote the harvest index (HI). This study indicates that BSS is the most suitable sowing method for winter wheat production in North China.

The current study evaluated the canopy cover competition for light and heat in a jujube–cotton intercropping system to measure the growth and yield performance of cotton, and the optimal cotton planting configuration. In this study, a two-year field experiment (2020 and 2021) was studied with different spacing configuration modes designed as follows: two rows of cotton (CM1) planted 1.4 m apart, four rows of cotton (CM2) planted 1.0 m apart, and six rows of cotton (CM3) planted 0.5 m apart, spacing intercropped jujube trees, respectively. The control treatment consisted of monocultured cotton (CK). The light-response curve was plotted using an LI-6400 XT photosynthesis instrument. Based on the modified rectangular hyperbola model, the photosynthetic characteristics were fitted, and the dry matter distribution characteristics and yield were compared. The results showed that with the increase in photosynthetically active radiation, the net photosynthetic rate (Pn) of each growth phase decreased first and then increased rapidly in the range of 0–200 μmol·m⁻²·s⁻¹ and then decreased slightly after the inflection point (light saturation point). The light-response curves of stomatal conductance and transpiration rate showed a linear relationship. The trend in the intercellular CO₂ concentration response curve was opposite to that of Pn. The maximum Pn (Pmax) of intercropped cotton was significantly impacted by configuration modes, of which CM2 treatment generated 1.8% and 22.8% higher Pmax than the CM1 and CM3 treatments. The cotton yield in the two years ranked as CK > CM3 > CM2 > CM1, and the average land equivalent ratio of CM2 was significantly higher than that of CM3 (22.4%) and CM1 (95.9%). The six-row configuration resulted in greater competition with the trees, which affected the accumulation of below-ground dry matter, while the four-row configuration formed a reasonable canopy structure, which ensured that more photosynthetic substances were distributed to the generative organs. The reasonable four-rows configuration mode may improve the photosynthetic efficiency of intercropped cotton economic yield.

Soil aggregates play an important role in affecting the structural stability of the soil, and it is important to understand the relationship between soil aggregate stability and crop yield in herbage-fruit tree intercropping systems. In this study, we determined the optimal spacing configurations for improving aggregate stability while increasing crop yields in alfalfa-jujube intercropping systems. The treatments included three intercropping patterns, i.e., the distances between alfalfa and jujube at 0.5 m (IP_0.5m), 1 m (IP_1m), and 1.45 m (IP_1.45m), along with monoculture alfalfa (CK_AL) and jujube (CK_JU). The results showed that IP_0.5m, IP_1m, IP_1.45m, and CK_JU effectively improved soil aggregate structure compared to CK_AL. The IP_1m spacing significantly increased the amounts of macro-aggregates (8.2%), and improved soil mechanical properties and aggregate stability among the other treatments, which was partly attributable to increased mean weight diameter (13.6%) and decreased soil aggregate destruction rate of water-stable aggregates (2.9%). The results of the principal component analysis showed that IP_1m treatments had a positive effect on PC1. The one-meter spacing of jujube-to-alfalfa intercropping optimized the soil structure while improving the yield (8.3%); thus, it can be considered the most suitable intercropping spacing configuration for growing alfalfa in jujube plantations.

Increasing agricultural yields and reducing greenhouse gas (GHG) emissions are the main themes of agricultural development in the 21st century. This study investigated the yield and GHGs of a jujube–alfalfa intercropping crop, relying on a long-term field location experiment of intercropping in an arid region. The treatments included four planting densities (D1 (210 kg ha⁻¹ sowing rate; six rows), D2 (280 kg ha⁻¹ sowing rate; eight rows), D3 (350 kg ha⁻¹ sowing rate; ten rows)) and four nitrogen levels (N0 (0 kg ha⁻¹), N1 (80 kg ha⁻¹), N2 (160 kg ha⁻¹), and N3 (240 kg ha⁻¹)) in the jujube–alfalfa intercropping system. The results showed that the jujube–alfalfa intercropping system is a the “source” of atmospheric CO₂ and N₂O, and the “sink” of CH₄; the trend of CO₂ fluxes was “single peak”, while the trend of N₂O and CH₄ fluxes was “double peak”, and there was a tendency for their “valley peaks” to become a “mirror” of each another. The magnitude of emissions under the nitrogen level was N3 > N2 > N1 > N0; the content of soil total nitrogen, quick-acting nitrogen, and the global warming potential (GWP) increased with an increase in the amount of nitrogen that was applied, but the pH showed the opposite tendency. The D2N2 treatment increased the total N, quick N, SOC, and SOM content to reduce the alfalfa GHG emission intensity (GHGI) by only 0.061 kg CO₂-eq kg⁻¹ compared to the other treatments. D2N2 showed a good balance between yield benefits and environmental benefits. The total D2N2 yield was the most prominent among all treatments, with a 47.64% increase in yield in 2022 compared to the D1N0 treatment. The results showed that the optimization of planting density and N fertilization reduction strategies could effectively improve economic efficiency and reduce net greenhouse gas emissions. In the jujube–alfalfa intercropping system, D2N2 (eight rows planted in one film 160 N = 160 kg ha⁻¹) realized the optimal synergistic effect between planting density and nitrogen application, and the results of this study provide theoretical support for the reduction in GHGs emissions in northwest China without decreasing the yield of alfalfa forage.

The bare row spacing between young jujube trees reduces resource use efficiency. Planting cotton between rows of jujubes can improve the efficiency of light, heat, water, and temperature resources. However, it is not clear how many rows of cotton between the jujube rows would be the most suitable pattern. A field study with different cropping systems was performed to investigate the land equivalent ratio (LER), the competition of cotton to jujube, and the sustainability index. The treatments included (1) monoculture jujube, (2) monoculture cotton, (3) jujube intercropped with two rows of cotton (J/C2), (4) jujube intercropped with four rows of cotton (J/C4), and (5) jujube intercropped with six rows of cotton (J/C6). The results showed that the LER under the J/C2, J/C4, and J/C6 systems were 1.17, 1.30, and 1.28, respectively. The LER and total yield were higher under J/C2 than under the J/C4 and J/C6 treatments. The overyielding rate of cotton was increased, while those of jujube were decreased with increasing rows of cotton. The competition between cotton to jujube was less than 0. The net, complementarity, selection effect, and sustainability index were significantly higher under J/C4 and J/C6 than under J/C2, with J/C4, showing stronger net effects. Both complementarity and selection effects contributed to the intercropping yield advantages. Comprehensively considering yield, economic efficiency, sustainability index, land use efficiency, and net effect, J/C4 is one of the most productive and sustainable planting patterns of jujube–cotton intercropping system in southern Xinjiang, which is the more ideal pattern in arid and semi-arid regions.