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【Objective】Excessive use of nitrogen fertilizers in maize production has led to environmental problems. Intercropping with leguminous green manure has been proposed as a sustainable agricultural practice that can improve soil nitrogen availability and crop nitrogen use efficiency. This study investigates the effect of intercropping leguminous green manure on nitrogen use of maize under different nitrogen application rates.【Method】A split-plot experimental design was used, with the main plots consisting of maize intercropped with common vetch (M||V) and sole maize cropping (SM). For cropping system, there were five nitrogen fertilizations: applying 360 (local practice, N360)), 270 (N270), 180 (N180) and 90 kg/hm2 (N90) of nitrogen fertilizer. No nitrogen fertilization was the control (N0). During the experiment, we measured soil nitrate and ammonium before sowing and at the harvest. We evaluated grain yield, nitrogen accumulation and allocation, nitrogen fertilizer use efficiency, and partial factor productivity to analyze the impact of intercropping with leguminous green manure on nitrogen use by the maize.【Result】Before sowing and at maize harvest, intercropping with leguminous green manure increased nitrate and ammonium concentrations in the 0-40 cm soil, with no significant difference between N270 and N360 in the intercropped maize belt. Compared with monocropped maize, intercropped with leguminous green manure increased dry matter accumulation, nitrogen accumulation and seed nitrogen allocation ratio by 5.8%, 9.1% and 6.2%, respectively. Dry matter and nitrogen accumulation of the intercropped maize in N270 and N360 were comparable. Intercropping significantly enhanced grain yield, nitrogen fertilizer utilization efficiency, and partial factor productivity after reducing nitrogen fertilization. Grain yield under M||V and N270 was not significantly different from that under M||V and N360 but was significantly higher than the monocropped maize in N360. Nitrogen utilization and partial productivity in M||V and N270 were significantly greater than those under both M||V and N360, and the monocropped maize in N360.【Conclusion】Intercropping leguminous green manure with maize with a 25% reduction in nitrogen fertilization improves nitrogen accumulation without compromising grain yield; it also improves nitrogen use efficiency and partial productivity.

Background Tobacco ( Nicotiana tabacum ) is an important plant model system that has played a key role in the early development of molecular plant biology. The tobacco genome is large and its characterisation challenging because it is an allotetraploid, likely arising from hybridisation between diploid N. sylvestris and N. tomentosiformis ancestors. A draft assembly was recently published for N. tabacum , but because of the aforementioned genome complexities it was of limited utility due to a high level of fragmentation. Results Here we report an improved tobacco genome assembly, which, aided by the application of optical mapping, achieves an N 50 size of 2.17 Mb and enables anchoring of 64% of the genome to pseudomolecules; a significant increase from the previous value of 19%. We use this assembly to identify two homeologous genes that explain the differentiation of the burley tobacco market class, with potential for greater understanding of Nitrogen Utilization Efficiency and Nitrogen Use Efficiency in plants; an important trait for future sustainability of agricultural production. Conclusions Development of an improved genome assembly for N. tabacum enables what we believe to be the first successful map-based gene discovery for the species, and demonstrates the value of an improved assembly for future research in this model and commercially-important species.

【Background】Agricultural production in Northern China faces two major challenges: water scarcity and low fertilizer efficiency. Improving management practices to enhance water and nitrogen use efficiency is therefore crucial for developing sustainable agriculture in this region. This study investigates how biochar application, irrigation, and nitrogen fertilization can be optimized to improve crop growth and yield. 【Method】A field experiment using a three-factor, three-level orthogonal design was conducted in a winter wheat field from 2021 to 2022. The experiment included three biochar application rates (0, 12.5, and 25 t/hm2), three irrigation treatments (75%, 100%, and 125% of evapotranspiration), and three nitrogen application levels (120, 180, and 240 kg/hm2). During the experiment, we measured grain yield, water use efficiency (WUE), and nitrogen use efficiency (NUE) of the crop. 【Result】Biochar application had an insignificant effect on water consumption, nitrogen accumulation, grain yield, WUE, and NUE. Irrigation levels did not significantly affect grain yield; however, increasing irrigation increased water consumption and decreased WUE, though these effects were not statistically significant. Increasing nitrogen fertilization significantly enhanced grain yield and nitrogen accumulation but reduced NUE. Statistical analysis indicated that nitrogen application was the primary factor affecting grain yield, nitrogen accumulation, and NUE, whereas irrigation and biochar application had no significant impact on these traits.【Conclusion】Irrigating at 75% of evapotranspiration did not reduce grain yield and resulted in the highest WUE. Due to high precipitation during the experiment, however, the optimal management strategy for winter wheat under drip irrigation in this study was 0 t/hm2 of biochar, 100% of evapotranspiration for irrigation, and 240 kg/hm2 of nitrogen fertilization.

AbstractMineral nitrogen fertilization has improved crop yield over the last century but has also caused air and water pollution. Reduction of nitrogen inputs and maintaining high yields are therefore essential to ensure a more sustainable agriculture. Improving the nitrogen use efficiency (NUE) of crops is therefore needed. Rapeseed, Brassica napus, depends on nitrogen fertilization due to its low NUE, with the ratio of plant nitrogen content to nitrogen supplied often not exceeding 60 %. Here, we review the major phenotypic traits associated with NUE in B. napus, with special emphasis on winter oilseed rape. We discuss the genetic diversity available and potential breeding strategies. The major points are the following: (1) rapeseed seed yield elaboration is complex, with overlapping phases of nitrogen uptake and remobilization during the crop cycle; (2) traits related to nitrogen uptake, such as root length and the amount of nitrogen absorbed after flowering, and traits related to nitrogen remobilization, such as the “stay-green” phenotype, have been identified as possible levers to improve NUE in rapeseed; (3) a substantial body of studies investigating the genetic control of NUE traits have already published and potential candidate genes identified; and (4) rapeseed genetic diversity may be enriched by exploiting interpopulation genetic variation and the closely related gene pools of Brassica rapa and Brassica oleracea.

Increasing maize grain yield has been a major focus of both plant breeding and genetic engineering to meet the global demand for food, feed, and industrial uses. We report that increasing and extending expression of a maize MADS-box transcription factor gene, zmm28, under the control of a moderate-constitutive maize promoter, results in maize plants with increased plant growth, photosynthesis capacity, and nitrogen utilization. Molecular and biochemical characterization of zmm28 transgenic plants demonstrated that their enhanced agronomic traits are associated with elevated plant carbon assimilation, nitrogen utilization, and plant growth. Overall, these positive attributes are associated with a significant increase in grain yield relative to wild-type controls that is consistent across years, environments, and elite germplasm backgrounds.

Aims Soil organic nitrogen (N) turnover is significantly influenced by elevated N deposition, precipitation and human-caused disturbances, but the underlying mechanism remains unclear. Identifying the relationships among the soil organic N fractions and N-mineralizing enzymes activities may advance our knowledge of the dynamics of soil organic N. Methods A field experiment was conducted in a semi-arid steppe and an abandoned cropland in northern China to investigate the effects of elevated N deposition and precipitation on soil organic N fractions and their relationships with N-mineralizing enzymes, i.e., protease, amidase, urease and N-acetyl-β-D-glucosaminidase (NAG) activities. Results The concentrations of N in various fractions were consistently lower in the abandoned cropland compared with the steppe. Nitrogen addition consistently decreased amino acid N content and activities of urease, protease and amidase in both sites but increased amino sugar N content and NAG activity in the steppe. Water addition decreased hydrolysable ammonium N content but increased amino sugar N content and activities of protease and NAG in both sites. Furthermore, urease and NAG activities were significantly positively correlated with the proportions of amino acid N and amino sugar N and, explained significant proportions of the variations in soil organic N fractions in the steppe. However, soil organic carbon (C), rather than N-mineralizing enzymes, explained greatest proportion of the variations in soil organic N fractions in the abandoned cropland. Conclusions The concurrent increase of N deposition and precipitation could promote the recovery of soil N (and C) losses in the abandoned cropland resulting from previous agriculture. Furthermore, in the steppe where NH4+ was available at relative high concentrations, enzymatic mineralization was the dominant route involved in potential soil organic N turnover. However, the direct route may be favored over the enzymatic mineralization route with decreasing availability of C relative to N in the abandoned cropland, which is driven by the need for C. These findings confirmed that the forms of N available, and the relative availability of C and N determine N uptake pathways both through enzymatic mineralization route and direct uptake route in the semi-arid grasslands.

Based on the theory of ecological crop nutrient deficiency and compensation effect, the nitrogen (N) deficiency at tillering stage and N compensation at young panicle differentiation stage in rice ( L.) was selected to study. Four N treatments were treated, and the effects of N deficiency and compensation were investigated on grain yield, N uptake and utilization and the physiological characteristics of rice. The results showed that the yield per plant presented an equivalent compensatory effect. Double N compensation led to superiority in the number of effective panicle per plant, increased the activity of nitrate reductase and glutamine synthetase. The content of endogenous growth-inhibitory hormone abscisic acid (ABA) decreased in the leaves, photosynthesis was enhanced, and the number of tillers per plant increased after double N compensation. During maturation stage, the panicle dry weigh in T1 (double N compensation at young panicle differentiation stage, after N deficiency at tillering stage) was higher than that in CK1 (constant supply of N throughout different stages of growth) and the biomass per plant in T1 increased by 1.47% compared with CK1. N contents in all organs, N accumulation, and total N content were all higher in T1 during maturation stage. Moreover, N agronomic efficiency, N physiological efficiency, and N partial factor productivity were optimized for T1 and CK2 (constant N compensation at young panicle differentiation stage, after N deficiency at tillering stage) compared with CK1. This study contributes to the understanding of the physiological mechanisms underlying the compensation of N deficiency in rice.

The spring form of rye can be grown on soil with relatively low utility value and in areas where winter rye becomes damaged during the winter. Under conditions of soil with low sorption complexes, it is important to adopt the right nitrogen application strategy to achieve high fertilizer efficiency (high yield). This study determined the weight of the separated parts of spring rye, productivity of 1 kg of nitrogen introduced into the soil with mineral fertilizer (E), N content (Nc), N uptake (Nup), N uptake per day (Nup/day), nitrogen use efficiency (NUE), nitrogen utilization efficiency for yield (NutEY), and the nitrogen harvest index (NHI) in six stages of development: BBCH 22, BBCH 33, BBCH 51, BBCH 65, BBCH 75 and BBCH 91. NutEY and NHI were calculated in two ways, with and without including the N accumulated in the roots, and were designated NutEY_1 and NutEY_2 and NHI_1 and NHI_2, respectively. Rye was fertilized once before sowing with 120 kg N ha −1 (N1) and with the same amount split into two portions, i.e. 60 + 60 kg N ha −1 (N2), and into three portions: 40 + 40 + 40 kg N ha −1 (N3). There was also a control treatment without nitrogen application (N0). The first portion was always applied before sowing, and the second and third as top dressing. In most cases, both the stage of development and the nitrogen treatments significantly influenced the values of the spring rye parameters. Split application of nitrogen in two or three portions increased the weight of the whole ears, including the grain, and the whole biomass of spring rye harvested at the fully ripe stage, without significantly altering the weight of the roots or straw. At this development stage, split application of nitrogen did not significantly affect the Nc value in any of the separated parts of the plant. Following the application of nitrogen in three portions, the NutEY_2 values were lower than after application in two portions, while values for NutEY_1, NHI_1, NHI_2, grain yield, whole biomass of spring rye, and Nc and NUE for the grain and whole plant were similar, and the Nup value was lower. On average for the entire growing period, the E value for the grain were not significantly altered by splitting nitrogen application into two or three portions, but the values for the whole spring rye biomass were higher following N application in two or three portions than after a single application. During the growth and development of spring rye, there was an increase in total biomass, total Nup, and NUE, and a decrease in average Nc in the whole plant and in Nup/day. In most cases, the inclusion of the roots in the calculation of NutEY and NHI did not result in statistical differences compared to their calculation without the roots.

Oilseed rape is one of the most important dicotyledonous field crops in the world, where it plays a key role in productive cereal crop rotations. However, its production requires high nitrogen fertilization and its nitrogen footprint exceeds that of most other globally important crops. Hence, increased nitrogen use efficiency (NUE) in this crop is of high priority for sustainable agriculture. We report a comprehensive study of macrophysiological characteristics associated with breeding progress, conducted under contrasting nitrogen fertilization levels in a large panel of elite oilseed rape varieties representing breeding progress over the past 20 years. The results indicate that increased plant biomass at flowering, along with increases in primary yield components, have increased NUE in modern varieties. Nitrogen uptake efficiency has improved through breeding, particularly at high nitrogen. Despite low heritability, the number of seeds per silique is associated positively with increased yield in modern varieties. Seed weight remains unaffected by breeding progress; however, recent selection for high seed oil content and for high seed yields appears to have promoted a negative correlation (r= –0.39 at high and r= –0.49 at low nitrogen) between seed weight and seed oil concentration. Overall, our results reveal valuable breeding targets to improve NUE in oilseed rape.