Effects Of Nitrogen Application Rate Research Articles

Multi-objective optimization of farmland water level and nitrogen fertilization management for winter wheat cultivation under waterlogging conditions based on TOPSIS-Entropy

Aiming at the problems of reduced winter wheat yield and aggravation of nitrogen leaching pollution caused by the waterlogging in the Middle-Lower Yangtze Plain, China, a two-year field experiment with three farmland water levels (W40, W60, W80) and three nitrogen application rates (N150, N225, N300) as well as a non-waterlogged treatment (CK) was carried out, to investigate the coupling effects of farmland water level and nitrogen application rate on the plant growth, grain yield, crop water productivity (WPC) and nitrogen load with waterlogging conditions. Three man-made waterlogging events were applied at winter wheat jointing-booting stage, heading-flowering stage and grain filling stage, respectively. The results indicated that with the farmland water level decreased from −40 cm to −60 cm and the nitrogen application rate increased from 150 kg∙ha−1 to 225 kg∙ha−1, the plant height, aboveground dry matter, leaf area index, spike length, grain yield, effective panicles, grain number per ear, 1000-grain weight and WPC in the waterlogging field increased significantly. However, since the nitrogen application rate exceeded 225 kg∙ha−1 and farmland water level lowered more than −60 cm, the favorable effects of nitrogen application rate and farmland water level for winter wheat growth and production reduced. Additionally, both the nitrogen load and partial factor productivity of nitrogen (PFPN) increased with the decline of farmland water level, while the nitrogen load increased and the PFPN decreased with the increasing nitrogen application rate. The raise of nitrogen rate from 150 kg∙ha−1 to 225 kg∙ha−1 was beneficial to plant growth, however, the increase of nitrogen application resulted in the decrease of PFPN and increase of drainage nitrogen loads. Compared with the water farmland water level of −40 cm and nitrogen application rate of 150 kg∙ha−1, the increase of nitrogen application rate and the decrease of farmland water level in the range of 50%-100% resulted in yield raise by 5.78%-32.29% approximately and the increase of nitrogen load by 36.20%-178.44% approximately. The comprehensive evaluation with TOPSIS-Entropy method for plant growth, grain yield, WPC, PFPN and nitrogen loads suggested that, the appropriate nitrogen application rate for winter wheat in the waterlogging areas of Middle-Lower Yangtze Plain in China was 225 kg∙ha−1, and the proper farmland water level was lowering to −80 cm in wet year and −60 cm in dry year within 3 days after waterlogging.

Chemical composition and quality of rapeseed meal as affected by genotype and nitrogen fertilization

Rapeseed meal (RSM) is known for its high nutritional quality as animal feed. However, there has been little studies on the effect of nitrogen fertilization on RSM chemical composition, mainly neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), and ash content. Therefore, this study was carried out to evaluate the effect of nitrogen application rate on chemical composition of RSM in interaction with different spring rapeseed varieties (Brassica napus L). A field experiment was conducted during 2018/19 cropping season at the experimental station of the Ecole Nationale d’Agriculture de Meknès” according to a split-plot design with three replications, using six nitrogen application rates, as main plot, and six rapeseed varieties, as subplot. After seeds harvest and oil extraction, meals derived from the different treatments were used in this study. Results showed that increasing nitrogen rate from 0 to 120 kg N ha−1 led to a significant rise in meal yield up to 74.58%. A positive effect of nitrogen fertilization was observed on dry matter, protein content and ash content, recording the highest values at 120 kg N ha−1 treatment. However, cellulose and lignin content were affected negatively by nitrogen fertilization. The nitrogen supply of 150 kg N ha−1 resulted in a reduction of ADF and ADL contents by 23% and 28%, respectively, compared to the unfertilized control (N0). Variability within rapeseed varieties for all parameters except dry matter and ADL content was highlighted.

Effects of Nitrogen Application Rate on Dry Matter Weight and Yield of Direct-Seeded Rice under Straw Return

Straw is an agricultural byproduct that results from the production of many crops, such as cereals, yet it is often considered a waste product. However, straw has both historical precedent and future potential as an agricultural resource. In this study, we aimed to determine the effects of returning straw to the soil on rice cultivation. To this end, we used the hybrid rice variety Luliangyou Jingling as the test material to study the effect of straw return under four different nitrogen application levels (0 kg N (N1), 120 kg N/hm2 (N2), 150 kg N/hm2 (N3), and 180 kg N/hm2 (N4)) on rice tillering dynamics, leaf area index (LAI), dry matter accumulation, and yield. We found that rice under straw return had a higher number of effective panicles, along with a higher number of grains per panicle, compared to those without straw return. Additionally, the tiller number, LAI, total dry matter, and yield of rice in each main growth period under straw return were higher than those without straw return, and these values increased with an increase in nitrogen application rate. The yield was the highest at 9520.63 kg/hm2 without straw return, while the highest yield with straw return was achieved at 10,738.26 kg/hm2. Our results revealed the optimal nitrogen application level for high yield of two-line direct-seeded rice under straw return, which provides a theoretical reference for the precise reduction of fertilizer application in rice cultivation.

Competition for nitrogen between plants and microorganisms in grasslands: effect of nitrogen application rate and plant acquisition strategy

Competition for nitrogen between plants and microorganisms in grasslands: effect of nitrogen application rate and plant acquisition strategy

Effects of Nitrogen Application Rate and Plant Density on Severity of Tar Spot of Corn

Tar spot of corn, caused by the fungus Phyllachora maydis, is an economically important foliar disease recently reported in the United States and Canada. Due to the recent introduction of Phyllachora maydis, the impacts of cultural management practices on disease development are still unknown. Separate field studies were conducted to determine the effects of nitrogen (N) application rate and plant density on disease development. Field trials were conducted across six site years in Michigan with two corn hybrids of differing disease susceptibility. The relative area under the disease progress curve was used to compare disease development between N application rates and plant densities. Nitrogen application rate had no significant effect on disease at any location. Plant density and disease had a significant ( P < 0.05) inverse relationship at five of six site years, with an average 41% decrease in the relative area under the disease progress curve for every 1,000 plants per hectare increase. The economically optimal planting density ranged from 73 to 77 thousand plants per hectare for US$150 to 300 per metric ton corn prices, demonstrating that relatively low planting densities were more profitable despite greater disease. Therefore, other disease management practices including hybrid selection may be more effective at protecting yield than increasing plant density.

Effects of Nitrogen on Photosynthetic Productivity and Yield Quality of Wheat (Triticum aestivum L.)

This study aims to understand the influence of chlorophyll fluorescence parameters on the yield of winter wheat in some areas of China. Nitrogen (N) application is believed to improve photosynthesis in flag leaf, which ultimately increases the final yield. The experiment was conducted in the wheat experimental base of Shanxi Agricultural University in Taigu, Shanxi Province, China; before sowing, four N application rates were set—N0, N120, N150, and N210 kg ha–1 of the Yunhan-20410 variety from 2019 to 2022. The results from different parameters of research showed that the organic manure partial substitution for chemical fertilizer increased post-anthesis N uptake by 16.4 and 81.4%, thus increasing the post-anthesis photosynthetic capacity and delaying leaf senescence. N150 treatment can improve dry matter (DM) accumulation, thus promoting the increase of the yield. The maximum net photosynthesis PN value of the booting stage and flowering stage indicated that nitrogen application could significantly improve the photosynthetic rate of wheat leaves, among which medium nitrogen treatment had the most significant promoting effect. The single-photon avalanche diode (SPAD) value of the leaf of wheat in each treatment increased rapidly in a small range from the jointing stage to the booting stage, respectively. The grain yield under N fertilizer partial substitution for N fertilizer treatment increased by 23%. According to the different significance test, the effects of nitrogen application rate on net photosynthesis PN of winter wheat were extremely significant at all growth stages, indicating that changing the population distribution mode and nitrogen level could effectively improve leaf photosynthetic performance and that N150 level was the best.

Effect of Nitrogen Application Rate on Grain Yield, Dry Matter and Nitrogen Accumulation and Remobilization in a Winter Wheat-Fresh Maize Cropping System

Three-harvest in two years is a traditional farming system in the Jinzhong Basin of Shanxi Province of the eastern Loess Plateau in China. Recently, an innovative farming system of winter wheat-fresh maize with two-harvest per year, making full use of temperature and light resources, is proposed. However, there is little known of the optimal nitrogen application rate for the innovative farming system to increase crop yield and improve ecological environment. In current study, six nitrogen application rates were carried out, consisting of winter wheat/fresh maize season 0/0 kg·ha-1 (N0, Control), 75/75 kg·ha-1 (N75), 150/150 kg·ha-1 (N150), 225/225 kg·ha-1 (N225), 300/300 kg·ha-1 (N300) and 375/375 kg·ha-1 (N375). The grain yield, dry matter and nitrogen accumulation and remobilization were analyzed to determine the optimal nitrogen application rate in the winter wheat-fresh maize cropping system in the Jinzhong Basin. The results showed that in the winter wheat and fresh maize season, compared with the N0, N75 and N375 treatments, total dry matter accumulation at winter wheat maturity and fresh maize harvesting increased significantly by 82.9%-94.5% and 26.1%-197.1%, respectively, and dry matter remobilization in leaves and stem+sheath (+tassel) increased significantly under the N150 treatment. Total nitrogen accumulations under the N150, N225 and N300 treatments increased significantly by 58.2%-162.9% and 55.7%-301.7% compared with those under the N0 and N75 treatments, respectively. Nitrogen remobilization in the kernel and stem+sheath (+tassel) under the N150 treatment increased significantly compared with the N0 and N75 treatments. In addition, nitrogen partial factor productivity of winter wheat and fresh maize under the N75 and N150 treatments increased significantly by 36.7%-534.1% and 45.2%-390.4% compared with the other nitrogen treatments, respectively, and nitrogen uptake efficiency also increased significantly by 79.1%-321.4% and 58.3%-239.5%, respectively. The yield of winter wheat and fresh maize under the N225 treatment was the highest, which significantly increased by 54.1% and 71.6% compared with that under the N0 treatment, respectively. In summary, nitrogen application rates of 150-225/150-225 kg·ha-1can be potential recommended use amounts with higher crop yield and nitrogen use efficiency in winter wheat-fresh maize cropping system in the Jinzhong Basin.

Effects of nitrogen application rate on the accumulation of 13C assimilates after flowering and water-nitrogen use efficiency of wheat under supplemental irrigation based on soil moisture.

This study aimed to explore nitrogen fertilizer management measures to synergistically improve wheat yields and water and nitrogen use efficiency under supplemental irrigation based on soil moisture in the Huang Huai winter wheat area. Wheat variety "Yannong 1212" was used as the test material. There were three nitrogen application levels, 150 kg·hm-2 (N1), 210 kg·hm-2 (N2), and 270 kg·hm-2 (the conventional nitrogen application rate in the Huang Huai winter wheat area, N3), with the relative soil water content of 0-40 cm of each treatment was supplemented to 70% at the jointing and flowering stages. We investigated the effects of nitrogen rates on photosynthetic characteristics of flag leaves after flowering, 13C assimilate accumulation and transport, and water and nitrogen use efficiency after flowering of wheat. The results showed that photosynthetic capacity of flag leaves in the N2 and N3 was significantly higher than that in N1 14-35 days after flowering, and that there was no significant diffe-rence between N2 and N3 treatments. The 13C isotope tracing results showed that the translocation amount of 13C assimilates in vegetative organs in N2 was 12.1% and 7.1% higher than that in N1 and N3, respectively. The distribution amount of 13C assimilates in grains at maturity was 10.1% and 5.3% higher than that of N1 and N3, respectively. The amount of nitrogen fertilizer affected water consumption, water consumption proportion, and total water consumption in different growth stages of wheat. Water consumption during the whole growth period showed no difference between N2 and N3 treatments, but both were significantly higher than that for N1. Water consumption and water consumption proportion of N2 were higher from the jointing to maturity stages, water use efficiency of N2 was 7.5% and 4.8%, and grain yield was 4.7% and 10.9% higher than that of N3 and N1 treatments, respectively. The partial productivity of nitrogen fertilizer was 34.6% higher in the N2 than that of N3. Considering wheat grain yield and water and nitrogen use efficiency, 210 kg·hm-2 nitrogen application was the best rate under water-saving condition of supplementary irrigation after soil moisture measurement in the study area.

Response of Rice Yield and Grain Quality to Combined Nitrogen Application Rate and Planting Density in Saline Area

To determine the combining effects of nitrogen application rate and planting density on rice yield and grain quality formation under salinity conditions, a field experiment was conducted in the coastal saline area using Oryza sativa L. cv. Nangeng 9108 from 2019 to 2020. The experiment was designed with six nitrogen rates (0, 210, 255, 300, 345, and 390 kg ha−1; denoted as N0-N390, respectively) and two transplanting densities (334,000 and 278,000 hills ha−1; denoted as D1 and D2, respectively). The results indicated that, with the increase of nitrogen input rate, the panicles number and spikelets per panicle increased first, subsequently decreased, and peaked under 300 kg ha−1 N, whereas the filled-kernel rate and grain weight displayed a decreasing trend. The panicle number and grain weight were higher under D1 treatment compared to those under D2 treatment, while the spikelet number per panicle and the filled-kernel rate displayed an opposite trend. The grain yield displayed highest under N300D1 treatment among all treatments, accompanied by the highest agronomic N use efficiency, and the actual yield reached 8060.4 kg ha−1 and 7869.8 kg ha−1 in 2019 and 2020, respectively. Increased nitrogen application rate significantly improved the grain processing quality and nutritional quality, while reducing the appearance quality and cooking/eating quality. Higher transplant density was conductive to grain nutritional quality, but notably reduced the processing quality, appearance quality and cooking/eating quality. Overall, a combination of 300 kg ha−1 nitrogen rate and 334,000 hills ha−1 planting density was recommended for relatively higher rice yield and better grain quality in the saline area.

Effect of nitrogen application rate under organic and conventional systems on rice (Oryza sativa L.) growth, grain yield, soil properties, and greenhouse gas emissions

The use of appropriate nitrogen (N) rates is important to optimize organic rice yield potential while minimizing environmental impact and input costs. A greenhouse experiment was conducted to identify the optimal N rate for organic and conventional rice and determine its effects on rice yield, soil properties, and greenhouse gas emissions. Six N rates (0, 50, 100, 150, 200, and 250 kg ha−1) and two cropping systems (organic, conventional) were included in this study. Plant dry biomass, panicle number, and yield of conventional rice linearly increased with increasing N rate from 0 to 250 kg ha−1, whereas those of organic rice increased significantly with increasing N rate until 200 kg ha−1. Conventional rice had a significantly taller plant, whereas organic rice had a significantly greater tiller number. At the optimal N rate, the panicle number and yield of organic rice were 77.3% and 92.7% of those of conventional rice, respectively. CO2 and CH4 emissions peaked at the reproductive stage, whereas N2O emissions peaked at the vegetative stage. Global warming potential (GWP) increased with increasing N rate and peaked at 200 and 250 kg N ha−1, respectively, in the organic and conventional system; however, greenhouse gas intensity (GHGI) was not affected by N rate in both systems. Of the measured soil parameters, total microbial biomass (TMB) was significantly correlated to plant growth, yield, and GWP. Our study indicated that the optimal N rate was 200 kg ha−1 for organic rice and 250 kg ha−1 or higher for conventional rice to approach yield potential.

Effects of Nitrogen Application Rates and Irrigation Regimes on Root Growth and Nitrogen-Use Efficiency of Maize under Alternate Partial Root-Zone Irrigation

Root growth and its adaptation are quite important for efficient use of water and nutrients. The present study investigated the effects of alternate partial root-zone irrigation (APRI) coupled with nitrogen application on root growth and nitrogen-use efficiency (NUE) of maize (Zea mays L.). Treatments (conducted at Wuwei City, northwest China) included APRI with controlled irrigation at 45%, 65%, and 80% of field capacity (FC) (W1, W2, and W3, respectively) coupled with nitrogen application rate of 100, 200, and 300 kg N ha−1 (N1, N2, and N3, respectively). The study found a significant interaction effect of irrigation regimes and nitrogen application rates on maize root growth and NUE. Compared with N2, N3 did not increase the length, surface area, weight, and volume of roots at the filling and maturity stages under W2, while it did under W3, which suggests that increasing nitrogen application rates did not compensate for the adverse effect of drought on root growth. In addition, NUE positively correlated with these root morphological parameters but negatively with the root-to-shoot ratio at the filling and maturity stages. The W2N2 treatment with moderate soil moisture and relatively high soil nitrate-nitrogen promoted total root growth and deeper roots and optimized vertical root distribution, with a low root-to-shoot ratio, resulting in the greatest NUE. These results suggest that moderately controlled irrigation (W2) combined with a reasonable nitrogen rate (N2) improves root growth and optimizes root distribution, resulting in a high NUE in maize under alternate partial root-zone irrigation.

Response of winter wheat yield, nitrogen use efficiency and soil nitrogen balance to rainfall types and nitrogen application rate in dryland

<p id="C3">To study the effects of nitrogen application rate on grain yield, nitrogen utilization, and soil nitrogen balance of dryland winter wheat fields under different rainfall types, we explored the optimal nitrogen input levels for stable yield and high efficiency of winter wheat in the Weibei highland of North China, which could provide a theoretical basis for efficient fertilization. Five nitrogen treatments including 0, 60, 120, 180, and 240 kg hm^-2 (designated as N0, N60, N120, N180, and N240, respectively) were arranged in Heyang County, Shaanxi Province from 2017 to 2020. The three-year <italic>in situ</italic> experiment were as follows: (1) Different rainfall types had significant impact on yield and economic profits of winter wheat. Compared with the normal and dry year, the yield of the humid year was increased by 33.6% and 113.3% and economic profits were increased by two to three times or more. Nitrogen fertilizer recycling and agronomic efficiency of winter wheat had similar change patterns with yield, and the nitrogen fertilizer recycling, and agronomic efficiency were increased by 4.7%, 0.6 kg kg^-1 (normal year), and 11.9%, 2.5 kg kg^-1 (dry year) in the humid year compared with the normal and dry year. (2) Regardless of the rainfall type, the yield and nitrogen fertilizer recycling and agronomic efficiency of winter wheat increase first and then decrease with the increase of N application. The highest values were found under N180 treatment in both humid and normal years, and the NO₃^--N accumulation in 0-100 cm layer after wheat harvest were 108.9 and 113.6 kg hm^-2, respectively. In dry year, the NO₃^--N accumulation under N120 treatment in 0-100 cm layer after wheat harvest was 100.8 kg hm^-2 reaching the highest value. (3) The threshold of nitrogen input was determined by the best economic benefit and the highest yield, the nitrogen application rates in humid year, dry year, and normal year were 158.9-166.5, 121.2-130.0, and 148.1-155.7 kg hm^-2, respectively; The threshold of nitrogen input was determined by the balance of soil nitrogen pool and the maximum nitrogen uptake, the nitrogen application rates in humid year, dry year, and normal year were 166.5-190.3, 109.6-147.7, and 153.5-198.9 kg hm^-2, respectively. Considering the high yield and high efficiency of winter wheat and low soil nitrogen loss, we concluded that when the nitrogen application rates in humid year, dry year, and normal year were 158.9-190.3, 109.6-147.7, and 148.1-198.9 kg hm^-2, respectively. It was the suitable nitrogen application rate for both high yield and good environmental benefits, which could be benefit for reference in the production of this region.

Effects of Nitrogen Application Rate Under Straw Incorporation on Photosynthesis, Productivity and Nitrogen Use Efficiency in Winter Wheat.

Developing a nitrogen fertilizer (N) reduction method under straw incorporation is essentially important for increasing wheat productivity in terms of improved fertilizer use efficiency and high yield in semiarid areas. A two-year field experiment, with five different nitrogen application rates: control (without N application, N0), low N (75 kg ha–1, N75), medium N (150 kg ha–1, N150), high N (225 kg ha–1, N225) and excessive N (300 kg ha–1, N300), was conducted in 2018 and 2019 to quantify their impacts on the photosynthetic characteristics, nitrogen utilization (in terms of N accumulation, distribution and transportation, and residual soil NO3–-N) and productivity of winter wheat. There was a significant impact of N rates on photosynthetic traits, and N accumulation in different organs. As compared with the N300, N150, and N225 improved the photosynthetic characteristics, increased N accumulation in grains by 5.55 and 10.97%, the N contribution proportion of that accumulated after anthesis by 67.90 and 115.56%, and reduced residual N by 62.50 and 46.48%, respectively, thereby effectively improved N absorption efficiency and N contribution rates. Grain yield remained slightly or unchanged among N treatments. Although N0 and N75 treatments reduced the nitrate-N leaching but caused a significant reduction of 18.13 and 28.37%, respectively, in grain yield. From these results, we conclude that N application at 150 and 225 kg⋅ha–1 under straw incorporation was the most effective fertilization method in achieving the higher photosynthetic characteristics, improving NUE and grain yield. This study provides theoretical and practical guidance for wheat production techniques.

Simulation of the responses of spring wheat yield to the rates and depths of nitrogen application in dryland based on APSIM model

Nitrogen limitation is an important factor for the improvement of crop water production potential in rain-fed areas of the Loess Plateau. The reasonable deep application of nitrogen fertilizer is a promising method to increase yield of rain-fed crop. Based on APSIM model, this study simulated spring wheat yield under different nitrogen application rates and depths, by using meteorological observation data from 1990 to 2020 in the semiarid areas of central Gansu Province, aiming to provide theoretical reference for optimizing wheat fertilization strategy. The results showed that the determination coefficient of simulated spring wheat yield, biomass and soil water content in 0-200 cm soil profile was greater than 0.80, the normalized root mean square error was less than 0.2, and the model validity index was greater than 0.5. These results indicated that the model had good fitting and adaptability in the test area. Across all the levels within the experimental design, increasing nitrogen application rates could significantly increase the yield of spring wheat in different precipitation years, and increasing nitrogen application depth could significantly increase spring wheat yield in wet and normal years, but had no effect in dry years. The rate and depth of nitrogen application had significant interaction effects on spring wheat yield in wet and normal years, but not in dry years. According to the binary quadratic regression fitting equation, when the potential maximum yield reached 2749 kg·hm-2 in wet year, nitrogen application depth was 22.7 cm, and nitrogen application rate was 245 kg·hm-2. When the maximum potential yield reached 2596 kg·hm-2 in normal year, nitrogen application depth was 20.6 cm, and nitrogen application rate was 235 kg·hm-2. Integrating the effects of nitrogen application rate and depth on yield, biomass and agronomic efficiency of nitrogen fertilizer, and farmer's fertilizer application habits, the recommended nitrogen application depth was 20-23 cm, and nitrogen application amount was 120-150 kg·hm-2, which could further improve water productivity and nitrogen use efficiency of spring wheat in arid areas of central Gansu Province.

Effects of nitrogen application and brackish water irrigation on yield and quality of cotton

In order to alleviate the shortage of water resources for cotton (Gossypium hirsutum L.) planting in Xinjiang of China, a reasonable amount of nitrogen application under brackish water irrigation was sought. A two-year field experiment was conducted to investigate the effects of nitrogen application rate and irrigation water salinity on seed cotton yield, nitrogen partial factor productivity and fiber quality in Xinjiang under mulched drip irrigation in 2019 and 2020. In this study, we selected four nitrogen application rates (i.e., 100, 200, 300, and 400 kg N ha−1, respectively) and three irrigation water salinity (i.e., 1, 3, and 5 g L−1, respectively). Our results showed that nitrogen application rates and irrigation water salinity significantly affected the seed cotton yield, nitrogen partial factor productivity, micronaire, fiber length, fiber strength, uniformity index and elongation. As the salinity of irrigation water increased, seed cotton yield and nitrogen partial factor productivity increased first and then decreased, micronaire decreased, but fiber length, fiber strength, uniformity index and elongation increased. Moreover, seed cotton yield, micronaire, fiber length, fiber strength, uniformity index and elongation increased first and then decreased, and nitrogen partial factor productivity decreased with the amount of nitrogen application. The optimal combination of nitrogen application rate and irrigation water salinity were 200 kg N ha−1 and 5 g L−1 by principal component analysis. We concluded that the normalized relative value of seed cotton yield and comprehensive evaluation value was 0.85, when the nitrogen application rate and the irrigation water salinity were 197.04 ⁓ 237.94 kg N ha−1 and 3.60 ⁓ 3.88 g L−1, respectively.

Effects of nitrogen application rates on the spatio-temporal variation of leaf SPAD readings on the maize canopy

AbstractThe spatio-temporal variation of leaf chlorophyll content is an important crop phenotypic trait that is of great significance for evaluating crop productivity. This study used a soil-plant analysis development (SPAD) chlorophyll meter for non-destructive monitoring of leaf chlorophyll dynamics to characterize the patterns of spatio-temporal variation in the nutritional status of maize (Zea maysL.) leaves under three nitrogen treatments in two cultivars. The results showed that nitrogen levels could affect the maximum leaf SPAD reading (SPADmax) and the duration of high SPAD reading. A rational model was used to measure the changes in SPAD readings over time in single leaves. This model was suitable for predicting the dynamics of the nutrient status for each leaf position under different nitrogen treatments, and model parameter values were position dependent.SPADmaxat each leaf decreased with the reduction of nitrogen supply. Leaves at different positions in both cultivars responded differently to higher nitrogen rates. Lower leaves (8th–10th positions) were more sensitive than the other leaves in response to nitrogen. Monitoring the SPAD reading dynamic of lower leaves could accurately characterize and assess the nitrogen supply in plants. The lower leaves in nitrogen-deficient plants had a shorter duration of high SPAD readings compared to nitrogen-sufficient plants; this physiological mechanism should be studied further. In summary, the spatio-temporal variation of plant nitrogen status in maize was analysed to determine critical leaf positions for potentially assisting in the identification of appropriate agronomic management practices, such as the adjustment of nitrogen rates in late fertilization.

&lt;sup&gt;15&lt;/sup&gt;N Tracer-based Analysis on Nitrogen Utilization Laws of Rice Under Different Irrigation Modes

In order to promote the efficient and coordinated utilization of water and nitrogen in rice, the&nbsp; 15 N missing technology experiment was adopted to study the effects of nitrogen application rate (N 0 , N 160 , N 200 , N 240 ) and irrigation mode (Wet-dry alternation, conventional irrigation) on nitrogen absorption, transport, residue, loss and nitrogen utilization of super rice. The results showed that with the increase of nitrogen application rate, the accumulation of fertilizer nitrogen and total nitrogen in rice plants at different growth stages, and the accumulation of nitrogen in various organs at mature stage increased significantly, and the accumulation of nitrogen per panicle at mature stage was the highest, reaching 67.20%~69.02%. The transport amount of nitrogen from different sources in different vegetative organs of rice plants increased with the increase of nitrogen application rate, and the comparison of nitrogen transport amount in organs was as follows: leaf &gt; stem &gt; root; After full heading, the accumulation of nitrogen from different sources and its contribution rate to grain nitrogen per spike increased with the increase of nitrogen application rate, but with the increase of nitrogen application rate, the residual amount of soil fertilizer nitrogen increased significantly, the residual rate showed a downward trend, and the nitrogen loss rate increased significantly. Dry-wet alternate irrigation treatment can increase nitrogen accumulation in different organs of rice in different periods, improve nitrogen use efficiency and rice yield to a certain extent. This study summarized the laws of nitrogen absorption, utilization, residue and loss of rice under different irrigation conditions and different nitrogen application conditions, which provided a theoretical basis for efficient cultivation of rice.

Fungal communities are more sensitive to nitrogen fertilization than bacteria in different spatial structures of silage maize under short-term nitrogen fertilization

Soil microbial diversity plays key roles in plant nutrient acquisition and resilience. In recent years, interactions between plants and their associated microorganisms in soil have decreased due to the large-scale use of chemical fertilizers. Silage maize is one of the main silage feeds with high yield and rich nutrition. However, there is a lack of knowledge on how nitrogen application affects the soil (rhizosphere and bulk soil) and endosphere microbial communities of silage maize. In this study, the effects of nitrogen application rates on bacterial and fungal communities in the bulk soil, rhizosphere, and endophytic environment of silage maize were assessed. Our results showed that microbiome assembly along the soil-root continuum is shaped predominantly by spatial structures rather than by fertilization practice. From bulk soil to endophytic environment, the effects of nitrogen application on microbial communities decreased, and bacterial diversity and network coefficient consequently reduced. Moreover, nitrogen fertilization rates significantly affected fungal alpha diversity in bulk soil and endophytic environment, and nitrogen fertilization had greater impact on fungal community composition than bacterial in different sample types. The biomarkers of fungi sensitive to nitrogen treatment accounted for 25.5%, 11.4%, and 6.9% of all the taxonomic groups, respectively. The non-random collinearity analysis showed that Mortierellaceae, Sporormiaceae, and Geminibasidiaceae were the dominant fungal residing groups in bulk soil, rhizosphere, and endophytic environment, respectively. Therefore, the fungal community can be considered as an important indicator for silage maize in response to nitrogen application. In the N240 (240 kg N ha - 1) treatment, there was a more precise relationship between bacterial and fungal communities; however, this relationship weakened under higher nitrogen rates, and an increase in the nitrogen application rate weakened the interaction of the fungal community.

Effects of nitrogen application rate on phosphorus transformation in an Alfisol: Results from phosphate-oxygen isotope ratios

The effects of N application on P nutrient uptake by plants are well known. However, soil P transformation under the influence of N application and the underlying mechanisms are not yet clearly understood. In this study, we investigated the effect of N application on P uptake by crops and the soil P transformation process using the phosphate oxygen isotope technique combined with the sequential extraction method. The results showed that the rapeseed yield initially increased drastically with N application, but a yield leveling off effect was observed at the highest N level. After applying P fertilizer with a low δ18OP value (original δ18OP value of 12.9‰), we observed that P in P fertilizer was transformed primarily into the NaOH-Pi pool. The lowest N rate (75 kg ha−1) and the highest N rate (225 kg ha−1) promoted exchange between the NaOH-Pi pool and the NaHCO3-Pi pool. The moderate N rate (150 kg ha−1) possibly promoted the transformation of the NaOH-Po pool to the NaOH-Pi pool. In the highest N treatment, the δ18OP value of the 1 M HCl-Pi pool significantly increased (19.0‰) and changed toward equilibrium, but the pool size was decreased, suggesting that the highest N rate possibly enhanced the transformation of the otherwise stable P pool. Overall, these results suggested that the specific N application rate could promote the turnover and transformation of soil P, which partly accounts for the enhanced soil P bioavailability and the increased crop yield and possibly leads to a high risk of P losses into the environment.

Nitrogen management can inhibit or induce the sprouting of potato tubers: Consequences of regulation tuberization

Regulation of tuber dormancy and sprouting are pivotal for postharvest storage, sales, and seed breeding of potatoes (Solanum tuberosum L.). Nitrogen is an essential mineral nutrient required in potato production, which directly influences tuber development and quality. However, the effects of nitrogen on the post-harvest dormancy of potato tubers remain unclear, and their association with the initial tuber development are poorly understood. The aim of this study was to clarify the effects of nitrogen application rate on potato tuber dormancy and the associated physiological mechanisms. We obtained the tubers of different commercial potato cultivars (E shu3, Z shu5, and H shu3) at three nitrogen levels (0, 210, and 315 kg N ha−1) through field experiment, and then stored the tubers at room temperature (25 ℃) in the dark for 0–16 weeks. The dormancy period and alkaloid accumulation of potato tubers were analyzed, and the quality of seed tubers was evaluated by examining eye sprouting and replanting. We also conducted a pot experiment to explore the differences in tuber and stolen development of one potato cultivar (H shu3) at the three nitrogen levels. The carbohydrate and phytohormone contents in the apical bud meristem of dormant tubers and the enlarged subapical region of stolons were measured. The results showed that a reduction in the nitrogen application rate extended the dormancy period of potato tubers by 3–6 weeks and thereby reduced the risk of alkaloid accumulation caused by tuber sprouting, which was favorable for potato storage and sales. From the perspective of seed potato breeding, nitrogen application markedly increased the number of sprouting eyes, resulting in more stems and higher tuber yield after replanting. Compared to the control, nitrogen application promoted the sprouting of eyes at the apical bud of potato tubers, improved associated α-amylase activity and sucrose content, and increased gibberellin 1 (GA 1) content by 6.0 times. Nitrogen application also facilitated stolon elongation and growth, increased associated GA 1 content by 2.2 times, and delayed the enlargement of the subapical region to form tubers by 6–15 d. Taken together, the results indicate that nitrogen management (increasing or reducing nitrogen application rate) can be used as an agricultural practice to regulate potato tuber dormancy and sprouting. The intrinsic link between regulation of tuber dormancy by nitrogen application rate and its effects on tuber development is attributable to the regulation of tuberization. This research provides abundant physiological information for tuber dormancy and development in potatoes.