Cropping diversification, especially with legume inclusion, has been shown to improve soil organic carbon (SOC) sequestration. However, it remains unexplored how preceding intercropped leguminous green manure affect microbial activity and necromass C contribution to SOC under reduced nitrogen (N) input in subsequent crop rotations. A six-year field experiment was conducted with treatments including maize monoculture (M) and intercropping with lablab bean as green manure (M/L), followed by rapeseed (R) under zero, 100 % and 65 % of recommended N application. The treatments were designated as M-R0, M-R100, M-R65, and M/L-R65. Soils were collected from 0 to 20 cm topsoil and 20-40 cm subsoil after rapeseed harvest for analysis of SOC fractions, microbial necromass carbon (MNC), extracellular enzyme activities, and microbial community. The results showed that preceding maize/legume intercropping M/L-R65 significantly increased the content of SOC, total N, dissolved organic C and N by 14.3-34.1 % in the topsoil compared to M-R100. This increase was associated with higher microbial necromass C content driven by a shift towards K-strategy microorganisms that produce more recalcitrant necromass compounds. In contrast, subsoil SOC levels remained relatively stable in the M/L-R65, despite an increase in MNC content. The lower soil C/N and dissolved organic C/N ratios in the M/L-R65 treatment endorsed soil N enrichment-induced decomposition of particulate organic C (POC) in the subsoil. This was further corroborated by the strong and direct impacts of soil C to N stoichiometry on microbial C pools revealed by PLS-PM analysis. Microbial C use efficiency (CUE) was higher in reduced N input treatments in the subsoil, but this did not translate to increased SOC in the subsoil layer, likely due to the shift in fungal community towards r-strategists. Overall, the study suggests that preceding legume intercropping enhances SOC sequestration in the topsoil of low-N input rapeseed rotation systems through increased microbial necromass C inputs. Moreover, the responses of SOC pools across soil depths are mediated by shifts in microbial life-history strategies.

Leaf mass per area (LMA) and photosynthetic rate (A) explain fast-slow growth strategies in the worldwide leaf economic spectrum. Nitrogen (N) promotes A and rapid growth, while LMA responds to N supply in a genotype specific manner. Structural traits affect the relationship between LMA and A, and we hypothesized that N supply would affect structural traits and thus the coupling between LMA and A. We tested this hypothesis by measuring A, LMA, anatomical traits, and N allocation to various leaf components in nine Brassica napus cultivars with two N supply levels. Mesophyll cell density (ρcell) and palisade tissue thickness (Tp) predominantly influence the variability in LMA. Enhanced Tp increased LMA, chloroplast surface area exposed to intercellular airspace, and N allocation into Rubisco (Nrub), thereby positively affecting mesophyll conductance (gm) and A. Conversely, ρcell promoted LMA but negatively affected Nrub under N deficiency. Enhanced LMA promoted N allocation to cell wall (Ncw), causing decreased Nrub fraction and consequently A. This negative effect was relieved by the positive effect of Tp on A, which coupled the variation of LMA and A. The plasticity of Tp and ρcell regulating gm and the trade-off between Nrub and Ncw provides insights for simultaneous increases in LMA and A to promote rapid growth and resistance.

Ammonium (NH4+-N) is the predominant form of nitrogen (N) fertilizer, but poses a risk of NH4+ toxicity, adversely affecting plant growth. Photosynthesis, which is closely linked to biomass and yield, is inhibited by NH4+ toxicity, but this effect is alleviated with increasing supplied nitrate (NO3--N) fraction. To understand the mechanism behind NO3--N's alleviation of NH4+-N inhibition on photosynthesis, limiting factors for photosynthetic rate (A) and anatomical characteristics of Brassica napus, an essential oil crop that heavily relies on N fertilizer, were measured. Results revealed that the inhibition of NH4+-N toxicity on A and growth was aggravated under NO3--N deprivation. When the proportion of NO3--N was lower than that of NH4+-N, the decrease of A was dominated by mesophyll conductance (g(m)), with its reduction strongly correlated with increased distance between two neighbouring chloroplasts (Dchl-chl) and decreased chloroplast surface area exposed to intercellular airspace per unit leaf area (Sc). NO3--N supply promoted volume fraction of intercellular air space (f(ias)) and mesophyll surface area exposed to intercellular airspace per unit leaf area (S-m), furtherly enhancing Scand facilitating higher gm. Additionally, Dchl-chl, f(ias), and S-m were more closely related to leaf NO3--N concentration than to NH4+-N. Thus, NO3--N plays a crucial role in mitigating NH4+-N toxicity on A by regulating leaf mesophyll arrangement and morphology. Increasing the proportion of NO3--N in fertilizers provides a strategy for crops at the risk of soil NH4+-N toxicity to maintain high A, furtherly promoting yield and N use efficiency.

Harnessing beneficial plant-microbe interactions in the rhizosphere presents a promising strategy for plants to combat unfavorable environment. However, the mechanisms by which rapeseed (Brassica napus L.) genotypes regulate root-associated microbiota through root metabolites under nitrogen (N) deprivation has not been fully explored. To address this issue, we planted rapeseed genotypes with varying tolerance to N deficiency—G364, which is susceptible, and G294 and ZS11, which exhibit tolerance—under both N-starved (N0) and N-sufficient (N1) conditions in pots. As expected, G364 was the most susceptible to N deficiency, experiencing a 30.8 % reduction in dry biomass when subjected to N deprivation. In contrast, G294 exhibited the greatest tolerance to N-deficiency, with only a 14.1 % decline in biomass due to N deficiency, underscoring its superior N utilization efficiency. The rhizosphere bacterial microbiomes of these genotypes exhibited distinct patterns at the rosette stage. Under N deprivation, the bacterial classes that significantly enriched in the rhizosphere of G294 and ZS11 genotypes were Chloroflexia, Bacilli, TK10, Gammaproteobacteria, and Acidimicrobiia. These microbial enrichments were positively correlated with increased biomass and N uptake in rapeseed. Furthermore, the compositional shifts in the rhizosphere bacterial community were associated with greater intensity of metabolites like flavonoids, amines, terpenoids, steroids, hormones and transmitters etc. Taken together, our study underscores the pivotal role of root metabolites in harnessing the beneficial plant–microbe interactions, thereby potentially improving the N use efficiency of rapeseed. This insight is valuable for manipulating the rhizosphere microbiome for breeding crops aimed at developing varieties with enhanced N efficiency.

Improving the nutrient content of red soils in southern China is a priority for efficient rice production there. To assess the effectiveness of oilseed rape as green manure for the improvement of soil phosphorus nutrient supply and rice yield in red soil areas, a long-term field plot experiment was conducted comparing two species of rape, Brassica napus (BN) and Brassica juncea (BJ). The effects of returning oilseed rape on soil phosphorus availability, phosphorus absorption, and yield of subsequent rice under rice-green manure rotation mode were analyzed, using data from the seasons of 2020 to 2021. The study found that compared with winter fallow treatment (WT) and no-tillage treatment (NT), the soil available phosphorus content of BN was increased, and that of BJ was significantly increased. The content of water-soluble inorganic phosphorus of BJ increased, and that of BN increased substantially. Compared with the WT, the soil organic matter content and soil total phosphorus content of BN significantly increased, as did the soil available potassium content of BJ, and the soil total phosphorus content of BJ was significantly increased compared with NT. The soil particulate phosphorus content of BJ and BN was significantly increased by 14.00% and 16.00%, respectively. Compared with the WT, the phosphorus activation coefficient of BJ was significantly increased by 11.41%. The rice plant tiller number under the green manure returning treatment was significantly increased by 43.16% compared with the winter fallow treatment. The green manure returning measures increased rice grain yield by promoting rice tiller numbers; BN increased rice grain yield by 9.91% and BJ by 11.68%. Based on these results, returning oilseed rape green manure could augment the phosphorus nutrients of red soil and promote phosphorus availability. Rice-oilseed rape green manure rotation could increase rice grain yield.

Legume-inclusive cropping is increasingly appreciated for enhancing crop yield and sustainability. However, their impacts on subsequent oilseed rape productivity under reduced nitrogen (N) inputs have not been well explored. In a five-year field rotation experiment, oilseed rape was cultivated with N fertilizer at zero (MN0), recommended (MN100), and 35 % reduction (MN65) following maize monoculture or preceding lablab (Lablab purpureus (L.) Sweet) intercropping in addition to MN65 (IN65). The productivity and stability of subsequent oilseed rape, and relevant indices of soil fertility and N cycling enzymes were investigated. Compared with the MN0 control, the MN100, MN65 and IN65 treatments increased the rapeseed yield by 0.7- to 1.2-fold. Compared with MN100, MN65 decreased rapeseed yield by 21 % and N uptake by 16 % on average across years. However, preceding lablab intercropping (IN65) recovered yield and N uptake. Treatment IN65 increased soil total N content by 7 % and organic matter by 10 % compared to the monoculture treatments, corresponding to 18-25 % increase in the soil quality index by preceding pulse intercropping. Moreover, in parallel with the increase in soil urease activity, the soil nitrate content in IN65 markedly increased by 18-123 % compared with that in the MN65 or MN100 treatments at most stages of oilseed crop growth. Principal component analysis revealed that the IN65 treatment was well distinguished from the three monoculture treatments, which was attributed primarily to soil nitrate, organic matter, nitrate reductase activity, and microbial biomass N. This enhanced N turnover and availability, in turn, largely contributed to N uptake and yield recovery of subsequent rapeseed crops under reduced N input. Consequently, the yield sustainability and stability of rapeseed following lablab intercropping were greater than those following monoculture, as evidenced by the higher sustainability index (64 % vs. 49 %) and lower variation (20 % vs. 32 %). Overall, these findings indicate that lablab and maize intercropping enhances positive legacies for subsequent rapeseed productivity under reduced N inputs.

A coordinated increase in the photosynthetic rate (A) and photosynthetic nitrogen use efficiency (PNUE) is an effective strategy for improving crop yield and nitrogen (N) utilization efficiency. PNUE tends to decrease with increasing N levels, but there are natural variations. Consequently, leaf functional N partitioning in Brassica napus genotypes under different N rates was measured to explore the optimized N allocation model for synchronously increasing A and PNUE values. The results showed that genotypes whose PNUE increased with increasing N supply (PNUE-I) produced an approximate A value with a relatively low leaf N content, owing to reduced storage N (N-store) and close photosynthetic N (N-psn) content. Partial least squares path modeling showed that A was dominated by the N-psn content, and PNUE was directly influenced by A and N-store. The A value increased with the N-psn content until the N-psn content exceeded the threshold value. The boundary line of PNUE varied with the N-psn and N-store proportions, indicating that the optimum N-psn and N-store proportions were 51.6% and 40.3%, respectively. The N-store proportion of PNUE-I was closer to the thresholds and benefited from lower increments in Rubisco content and nonprotein form storage N content with improved N supply. Optimized N-store and N-psn trade-off by regulating increments in N-store content with increased N supply, thereby promoting coordinated increases in A and PNUE.

Peanut (Arachis hypogaea L.) is one of the most important crops produced worldwide. Peanut is the dominant crop in the typical upland red soil areas of China; however, phosphorus bioavailability in red soil is very low, which severely affects peanut production. To improve the phosphorus bioavailability, which substantially promotes the green development of peanut production, a peanut–green manure rotation field experiment was conducted with six treatments (milkvetch; radish; brassica rape; mustard rape; winter fallow and no-tillage), commencing in September 2017 in the red soil area of Jiangxi province, China. The results show that compared with no-tillage (NT) treatments, different green manure returning treatments had significant effects on soil pH, soil phosphorus components and available potassium content. The particulate phosphorus and soil available phosphorus contents in the green manure treatments were significantly higher than those in the winter fallow (WF) treatment. Compared with the WF treatment, the content of particulate phosphorous in brassica rape (BR), radish (R) and milkvetch (MV) treatments was significantly increased by 6.55%, 3.66% and 2.50%, respectively; the available phosphorus content in mustard rape (MR), BR, R and MV was significantly increased by 20.93%, 25.60%, 23.76% and 18.10%, respectively. In addition, the total phosphorus content of peanut shell in the MV and R treatment was significantly higher than that in the WF treatment, increasing by 33.47% and 60.66%, respectively. Compared with the WF treatment, the peanut biomass of MR, BR and R treatments increased significantly by 19.51%, 29.83% and 19.77%, respectively. The total phosphorus accumulation in all green manure treatments was higher than that in the WF treatment, and the MV treatment reached a significant level at 18.83%. Based on these results, the particulate phosphorus (PP) and available phosphorus were significantly affected by different green manure treatments; green manure amendment improves peanut phosphorus uptake. The use of green manure (especially milkvetch and brassica rape) can be recommended to improve phosphorus bioavailability and yield of peanut in red soil areas.

Under potassium (K) deficiency photosynthetic carboxylation capacities are limited, affecting the photosynthetic rate of plants. However, it is not clear how ionic K within plants regulates carboxylation capacities. Therefore, the photosynthetic rate (A), ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) characteristics, and cytoplasmic pH of Brassica napus leaves with different K levels were measured to evaluate the effects of K on the carboxylation capacity by regulating subcellular pH. The results showed that biochemical limitation dominates the decrease of A. There was a close positive correlation between A and the Rubisco maximum carboxylation rate (Vcmax), which was closer than that between A and the maximum electron transport rate. The thresholds of leaf K concentrations causing decreased A, Vcmax, and Rubisco initial activity were consistent and close to 1.0% in the hydroponic experiments and 1.2% in the field experiments. K deficiency resulted in decreased Rubisco activity, which reduced carboxylation capacity. Moreover, the Rubisco initial activities in vitro with sufficient K supply or under K deficiency all were significantly reduced when the pH was decreased. The cytoplasmic pH was kept neutral at 7.5 under sufficient K supply, and decreased as the leaf K concentration declined below the threshold. Acidified cytoplasmic environment caused by K deficiency could not maintain the pH balance of the chloroplasts, leading to decreased Rubisco initial activity and photosynthetic capacity.

【Objective】The aim of this study was to investigate the effects of nitrogen application on yield formation and nutrient utilization of oilseed (Brassica napus L.) under different cropping systems.【Method】A field experiment was carried out in Huanggang, Hubei Province. An oilseed variety ‘Zhongyouza19’ was used as the material, setting with two cropping systems (rice-oil rotation, RO; soybean-oil rotation, SO) and four nitrogen rates (N0, 0; N1, 90 kg·hm-2; N2, 180 kg·hm-2; N3, 270 kg·hm-2) in this study. The yield and its components, dry matter accumulation, agronomic traits, nitrogen content and seeds quality were measured.【Result】(1) The oilseed yield of SO was significantly higher than that of RO, and the pods per plant, seeds per pod and 1000-seeds weight of oilseed in different cropping systems all tended to increase significantly by increasing the amount of nitrogen. Compared with N0, the seed yield of RO increased by 176.68%, 436.49% and 835.40% under N1, N2 and N3 treatments, respectively, while that of SO increased by 123.96%, 344.46% and 547.25%, respectively. Compared with RO, the seed yield under SO increased by 62.09%, 31.33%, 71.79% and 12.21% under N0, N1, N2 and N3 treatments, respectively. (2) The root crown diameter, plant height, first effective branch height and branch number of SO oilseed were significantly higher than those of RO at maturity stage, and the increase in each agronomic trait index was significant under different cropping systems with the increase in nitrogen application; the root biomass and above-ground biomass of SO were significantly higher than those of RO at all growth stages, but the root shoot ratio was lower than that of RO. The root shoot ratio decreased significantly after seedling stage in both cropping system with increasing nitrogen application. (3) Nitrogen content and nitrogen accumulation in the root, pod shell, stalk and seeds of SO were higher than those in RO, and the increases in nitrogen content and nitrogen accumulation in each part were significant with the increase in nitrogen application; the apparent nitrogen recovery efficiency under SO was higher than that under RO, and the apparent nitrogen recovery efficiency under RO increased with the increase in nitrogen application. (4) Compared with the RO, the soluble sugar content of pod shell under SO was lower, while the amino acid content and amino acid/soluble sugar content were higher with the same nitrogen application. The soluble sugar content decreased, but the amino acid content and amino acid/soluble sugar content increased with the increase of nitrogen application. Therefore, the oil content of oilseed under SO was lower than that under RO due to the limitation of fatty acid synthesis substrate, and the oil content of seeds decreased significantly with the increase of nitrogen application in cropping system. Oil yield was the maximum in both cropping system at 270 kg·hm-2 nitrogen application level, 1 678.60 and 1 665.33 kg·hm-2 for RO, and 1 684.03 and 1 687.10 kg·hm-2 for SO, respectively, but the difference in oil yield between 180 and 270 kg·hm-2 nitrogen application for SO was not significant.【Conclusion】In conclusion, the nitrogen rate for RO could be controlled at about 270 kg·hm-2, but the nitrogen rate for SO could be controlled at about 180 kg·hm-2 to ensure higher nitrogen use efficiency and higher oil yield.

Carbon and water are two main factors limiting leaf expansion. Restriction of leaf growth by low availability of carbon or water is among the earliest visible effects of potassium (K) deficiency. It is not known how K is involved in regulating the rhythmic supply of these two substrates, which differ remarkably across the day-night cycle, affecting leaf expansion. We investigated the effects of different K regimes on the time courses of leaf expansion, carbon assimilation, carbohydrates, and hydraulic properties of Brassica napus. Potassium supply increased leaf area, predominantly by promoting night-time leaf expansion (>60%), which was mainly associated with increased availability of carbohydrates from photosynthetic carbon fixation and import from old leaves rather than improvement of leaf hydraulics. However, sufficient K improved leaf hydraulic conductance to balance diurnal evaporative water loss and increase the osmotic contribution of water-soluble carbohydrates, thereby maintaining leaf turgor and increasing the daytime expansion rate. The results also indicated an ontogenetic role of K in modifying the amplitude of circadian expansion; almost 80% of the increase in leaf area occurred before the area reached 66.9% of the mature size. Our data provide mechanistic insight into K-mediated diel coordination of rhythmic carbon supply and water balance in leaf expansion.

油菜是我国种植面积最大的油料作物,是国产食用植物油的重要来源.油菜生长过程可以优化土壤结构、增加土壤养分、培肥土壤地力,具有用地养地的特征优势.同时,因其具有较强的环境适应能力,可作为先锋作物改良障碍土壤.然而,近年来由于劳动力不足、种植效益低、农民种植积极性不高等因素,导致冬闲田面积逐年增加,冬季光温水土自然资源未能得到有效利用.而油菜作为冬季种植的油料作物,不与粮争地,是开发利用冬闲田最有潜力的作物.利用冬闲田发展油菜生产,不仅可以提升油料产量,还可以充分发挥其养地优势提高后茬作物产量品质、增加种植收益,对维护我国食用油供给安全、助力粮油兼丰及农业绿色可持续发展具有重要意义.本文结合我国油菜生产现状,针对南方稻区冬闲田油菜轮作的生产发展需要,综述了油菜用地养地(油用或肥用)的作物优势,旨在为因地制宜利用南方冬闲田发展油菜生产助力油料产能提升提供科学依据.

Leaf growth relies on photosynthesis and hydraulics to provide carbohydrates and expansion power; in turn, leaves intercept light and construct organism systems for functioning. Under potassium (K) deficiency stress, leaf area, photosynthesis and hydraulics are all affected by alterations in leaf structure. However, the connection between changes in leaf growth and function caused by the structure under K regulation is unclear. Consequently, the leaf hydraulic conductance (Kleaf ) and photosynthetic rate (A) combined with leaf anatomical characteristics of Brassica napus were continuously observed during leaf growth under different K supply levels. The results showed that Kleaf and A decreased simultaneously after leaf area with the increasing K deficiency stress. K deficiency significantly increased longitudinal mesophyll cell investment, leading to a reduced volume fraction of intercellular air-space (fias ) and decreased leaf expansion rate. Furthermore, reduced fias decreased mesophyll and chloroplast surfaces exposed to intercellular airspace and gas phase H2 O transport, which induced coordinated changes in CO2 mesophyll conductance and hydraulic conductance in extra-xylem pathways. Adequate K supply facilitated higher fias through smaller palisade tissue cell density (loose mesophyll cell arrangement) and smaller spongy tissue cell size, which coordinated CO2 and H2 O conductance and promoted leaf area expansion.

The utilization of crop straw is important for the green development of agriculture and the ecological environment. China’s agricultural planting structure is diversified and straw utilization has received increased attention. Here, in situ experiment with four types of crop straw (i.e., straw of oilseed rape, wheat, rice and corn) was conducted to analyze the effects of climate factors (i.e., accumulated temperature, AT) and straw returning methods on straw decomposition and the release of nutrients. The AT value was an important factor affecting straw decomposition and carbon, nitrogen, and phosphorus release. When straw was incorporated into the soil, the straw decomposition rate could be stimulated when the AT ≥ 600–740 °C. Under straw mulching, the decomposition rate could be further enhanced if the AT exceeded 960–1300 °C. At the end of the experiment, the decomposition and nutrient release rates increased by 39.7–148.7% and 5.8–171.5%, respectively, under straw incorporation compared to straw mulching. The differences under different returning methods in straw decomposition and nutrient release rates were higher in the summer–autumn stage (114.3–148.7% and 14.7–171.5%) than in the winter–spring stage (39.7–47.6% and 5.8–62.5%). The variance in the C/N ratio and the infrared characteristic peak of different straw types affected the decomposition rate and nutrient release characteristics. This study concludes that straw decomposition and nutrient release varied widely among different AT values, straw types, and returning methods.

Chlorosis at leaf margins is a typical symptom of potassium (K) deficiency, but inappropriate application of K with other nutrients often masks symptoms of K deficiency. A two-year field experiment was conducted to measure the interactive effects of N and K on leaf photosynthesis and dry matter accumulation and the resulting growth dilution effect on K concentration and leaf K deficiency symptoms. N application aggravated the imbalance of N and K nutrients and further exacerbated K deficiency symptoms under K limitation. Synergistic effects of N and K promoted plant growth, amplified the growth dilution effect, and reduced the critical K concentration in leaves. Using 90% of the maximum shoot biomass as a threshold, the critical K concentration was 0.72% at the recommended N (N180) fertilization level. The critical K concentration increased by 62.5% owing to the reduced biomass under insufficient N (N90) supply. In contrast, high N (N270) reduced the critical K concentration (0.64%), accelerating chlorophyll decomposition and exacerbating K deficiency symptoms. The basis of changing the critical K concentration by magnifying growth dilution effect was the functional synergistic effect of N and K on photosynthetic characteristics. Under insufficient N, the low maximum carboxylation rate (Vcmax) limited the net photosynthetic rate (An) and necessitated more K to maintain high CO2 transmission capacity, to improve the total conductance gtot /Vcmax ratio. High N supply increased gtot and Vcmax, possibly mitigating the effect of K reduction on photosynthesis. In conclusion, it is unwise to judge K status of plants only by K concentration without accounting for crop mass (or dilution effect), critical K concentration and deficiency symptoms are affected by N fertilization, and the synergistic effect of N and K on leaf photosynthesis is the foundation of maximal growth of plants under diverse critical K concentrations.

Potassium (K) regulates plant metabolism and enhances plant's ability to adapt to adversity. However, under different K deficiency stress, the net photosynthetic rate (An) was reduced, influenced by CO2 conductance or biochemical capacities. The interplay between metabolome and photosynthetic characteristics under K deficiency stress was analyzed to explore the mechanisms by which K regulates photosynthetic capacity. With increasing K deficiency stress, dominations limiting An varied from CO2 conductance to biochemical limitations. Multivariate analyses indicated that organic acids, amino acids and sedoheptulose-7-bisphosphate were significantly related to An, CO2 conductance and carboxylation rate. Under moderate K deficiency, organic acids were up-regulated. Acidification of subcellular compartments reduced sedoheptulose-1,7-bisphosphatase activity, inducing downregulation of sedoheptulose-7-bisphosphate and hindrance of ribulose bisphosphate regeneration. Moreover, increased CO2 shortage with increasing K deficiency induced a shift of increased citric acid to amino acid synthesis, causing excessive accumulation of amino acids. In addition, the reduced serine level indicated impaired photorespiration. These two changes triggered more serious reduction in photosynthetic capacity. The intimate, changes in photosynthetic capacities were tightly coupled with shifts in central C metabolism, which provides insights into the methods used to enhance An and plant's adaptability to abiotic stresses, through the regulation of C metabolites using molecular technology.

Excessive use of chemical fertilizers has led to a reduction in the quality of arable land and environmental pollution. Using green manure to replace chemical fertilizers is one of the most effective solutions. To study the effect of green manure on the requirement for nitrogen fertilizer in oilseed rape, a field experiment with maize–oilseed rape rotation was conducted. Green manure was intercropped between rows of maize and returned after the maize harvest, with no green manure intercropped as control. Different nitrogen fertilizer treatments (0, 65%, 75% and 100% N rates, respectively) were applied during the oilseed rape season. The results showed that with a 35% reduction in nitrogen application rate, the rapeseed grain yield was significantly higher with the maize intercropping with green manure returned to the field than with the maize monocropping treatment at the same nitrogen level. Under conditions of intercropping and return of green manure, compared with the full standard rate of nitrogen fertilizer treatment, a reduction in nitrogen application of 25–30% in the rape season had no significant effect on rape yield. The agronomic efficiency of nitrogen fertilizer on oilseed rape increased significantly, by 47.61–121%, with green manure incorporation. In addition, green manure incorporation significantly increased the soil organic matter content and the soil-available nitrogen content when chemical nitrogen fertilization was abandoned. Benefit analysis showed that a 25–35% reduction in chemical nitrogen fertilizer applied to oilseed rape crops could be achieved by intercropping green manure in the maize season before the sowing of rapeseed in the experimental area. In the long-term, this measure would increase nitrogen utility, reduce production costs, and have concomitant environmental benefits of improving the quality of cultivated land.

The seed yield of oilseed rape (Brassica napus), an important edible and industrial oil source, is derived mainly from the photosynthetic products of siliques. High temperatures in the pod-development stage threaten the oilseed rape production. Fertilization promotes the growth and yield of oilseed rape. However, it is unclear whether fertilization can alleviate the effect of the temperature on the yield. During 2017-2019 oilseed rape growing season, two oilseed rape cultivars with different K utilization efficiencies (KUtEs) were grown with four K fertilizer rates (0, 60, 120, and 180 kg ha-1) to study the association between the application of the stressresistance-related element K and silique canopy temperature of oilseed rape. Infrared imaging was used to determine the canopy temperature of the two cultivars at the silique development stage at different K application rates. Partial least squares path modeling (PLS-PM) was used to analyze the potential physiological mechanism of the increase in crop yield with K fertilization. The K fertilization reduced the canopy temperature, specifically, the canopy temperature variation (CTV), at the silique development stage (reduction of 1.3-3.0 degrees C by 1 % increase in K amount). A reduction of 1 degrees C in CTV increased the seed yield by approximately 417.6 kg ha-1. Nevertheless, the cultivar with a low KUtE required almost twice the K amount, compared with the cultivar with a high KUtE, to achieve the same consequent CTV reduction, and produced a lower seed yield at the same K application rate. The reduction in CTV was induced by an increased stomatal function (transpiration rate), which was accelerated by the K application. PLS-PM showed that the K application promoted seed yield by reducing the CTV and increasing the photosynthetic rate and biomass. The photosynthetic rate and biomass were directly affected by the CTV. Overall, the K fertilization combined with the high KUtE cultivars could efficiently maintain a stable canopy temperature microenvironment to promote oil production.

明确钾肥对冬油菜两种光合器官(叶片和角果皮)的演替和光合能力的调控,对于进一步理解钾肥促进油菜产量的机制具有重要意义.实验于2018-2019年油菜生长季的田间开展,通过监测不同施钾量下油菜(甘蓝型油菜华油杂9号)叶面积指数(LAI)和角果皮面积指数(PAI)的动态变化,结合光合能力变化,探究油菜主要光合器官对产量的影响.随着生育期推进,LAI逐渐增加,在花期达到最大,为3.4～4.8,此后迅速降低,而PAI快速增加,相同处理下最大PAI与最大LAI相当.钾肥施用对LAI和PAI调控作用一致,LAI和PAI均随施钾量增加而增加,PAI/LAI的比值不受施钾量影响.在各关键生育期,光合速率随施钾量增加而增加,在超过120 K2O kg/hm2后不再显著变化.在一天中,钾肥施用显著提高午间光合速率,缓解越冬期午休现象.LAI、PAI和光合能力与油菜籽产量显著相关,施钾显著提高油菜光合器官光合面积和能力,从而增加油菜籽产量.