N-fertilizer Rates Research Articles

Effect of Nitrogen and Municipal Solid Waste Compost on the Physicochemical Properties of a Calcareous Soil Under Wheat Cultivation

ABSTRACT Municipal solid waste (MSW) is an exciting source of organic matter (OM) for agricultural soil. In recent years, the application of MSW compost has received considerable attention. On the other hand, simultaneous use of organic and chemical fertilizers can lead to better plant growth and soil fertility. The main purpose of this study was to evaluate the impact of MSW compost and nitrogen fertilizer (N-fertilizer) on soil physicochemical properties. Treatments consisted of three levels of MSW compost 0, 10, and 20 t ha−1 (C0, C10, and C20), three rates of N-fertilizer 0, 100, and 200 kg ha−1 (N0, N100, and N200). Application of N-fertilizer and MSW compost alone or in combination significantly affected some physical and chemical properties of soil. The addition of N-enriched compost to the soil increases electrical conductivity (EC), N-NO3 − contents (in C20N200 treatment) and available iron (Fe) and zinc (Zn), field capacity (FC) and available water (AW) contents (in C20N100 treatment). While the bulk density (BD) of the soil decreased. Our results show that the use of MSW compost and N-fertilizer is a beneficial option for improving the physicochemical properties of soil, especially physical properties under arid and semi-arid conditions.

Does Nitrogen Fertilization Improve Nitrogen-Use Efficiency in Spring Wheat?

To investigate the effects and mechanism of prolonged inorganic nitrogen (N) fertilization on the N-use efficiency of spring wheat (Triticum aestivum L.), a long-term study initiated in 2003 was conducted. The study analyzed how N fertilization affects dry matter translocation, N translocation, soil NO3-N, and N-use efficiency. Five different N-fertilizer rate treatments were tested: N0, N52.5, N105, N157.5, and N210, corresponding to annual N fertilizer doses of 0, 52.5, 105.0, 157.5, and 210.0 kg N ha−1, respectively. Results showed that increasing N-fertilizer rates significantly enhanced the two-year average dry matter accumulation amount (DMA) at maturity by 22.97–56.25% and pre-flowering crop growth rate (CGR) by 17.11–92.85%, with no significant increase beyond 105 kg N ha−1. However, no significant correlation was observed between the dry matter translocation efficiency (DTE) and wheat grain yield. Both insufficient and excessive N applications resulted in an imbalanced N distribution favoring vegetative growth over reproductive growth, thus negatively impacting N-use efficiency. At maturity, the N-fertilized treatments significantly increased the two-year average N accumulation amount (NAA) by 52.04–129.98%, with no further increase beyond 105 kg N ha−1. N fertilization also improved the two-year average N translocation efficiency (NTE) by 56.89–63.80% and the N contribution proportion (NCP) of wheat vegetative organs by 27.79–57.83%, peaking in the lower-N treatment (N52.5). However, high-N treatment (N210) led to an increase in NO3-N accumulation in the 0–100 cm soil layer, with an increase of 26.27% in 2018 and 122.44% in 2019. This higher soil NO3-N accumulation in the 0–100 cm layer decreased NHI, NUE, NAE, NPFP, and NMB. Additionally, N fertilization significantly reduced the two-year average N harvest index (NHI) by 9.89–12.85% and N utilization efficiency (NUE) by 11.14–20.79%, both decreasing with higher N application rates. The NAA followed the trend of anthesis > maturity > jointing. At the 105 kg N ha−1 rate, the highest N agronomic efficiency (NAE) (9.31 kg kg−1), N recovery efficiency (NRE) (38.32%), and N marginal benefit (NMB) (10.67 kg kg−1) were observed. Higher dry matter translocation amount (DTA) and N translocation amount (NTA) reduced NHI and NUE, whereas higher NTE improved NHI, NUE, and N partial factor productivity (NPFP). Overall, N fertilization enhanced N-use efficiency in spring wheat by improving N translocation rather than dry matter translocation.

Pre Extension Demonstration of Soil Test Crop Response Based Recommended Phosphorus Fertilizer for Maize in Bako Tibe and Gobu Sayo Districts of Western Oromia, Ethiopia

Pre-extension demonstration of soil test crop response based phosphorus fertilizer recommendation for maize was conducted in Bako Tibe and Gobu Sayo districts with the objective of participatory demonstration of soil test crop response based phosphorus recommendation under farmers’ condition in 2022 cropping season. Two treatments were applied (T<sub>1</sub>) blanket Recommendation (T<sub>2</sub>) Soil Test crop response based recommended phosphorus fertilizer with improved maize (BH-661) variety. The trial was conducted on eleven farmers’ fields which were used as replications. Plot size for each treatment was 10m x 20m with the spacing of 35cm and 75cm between plants and rows respectively using seed rate of 25 kg ha<sup>-1</sup> and with recommended optimum N-fertilizer rate of 110 kg ha<sup>-1</sup>. In each PAs, one FREG unit comprising of 20 farmers were established. About 185 (139 male and 46 female) participants were take part on field visit based training held during physiological maturity of maize. The average total biomass with soil test crop response based Recommended phosphorus fertilizer was 32,385 kgha<sup>-1</sup> while blanket recommendation was 27,730 kgha<sup>-1</sup>. Again the average grain yield for STCRBPR was 7,205kg ha<sup>-1</sup> while blanket recommendation was 4,641kg ha<sup>-1</sup>. Similarly, the results of the economic analysis indicated that the use of p-fertilizer based on soil test crop response and the blanket suggestion with MRR 500.93% could yield net returns of 188,029.36 and 119348 ETB per hectare, respectively. As a result, the suggested phosphorus fertilizer based on soil test crop response should be expanded/scaled up to include additional maize producer farmers in the region and surrounding districts.

Evaluating the Effects of Reduced N Application, a Nitrification Inhibitor, and Straw Incorporation on Fertilizer-N Fates in the Maize Growing Season: A Field 15N Tracer Study

Reducing fertilizer-N rate, applying a nitrification inhibitor (NI), and incorporating straw are widely recommended to improve N use efficiency of crops and decrease N losses. A field 15N tracer study was conducted to compare their effectiveness on fertilizer-N fates during the maize growing season in Northeast China. The following six treatments were used: (1) no N fertilization (control); (2) 200 kg urea-N ha−1 (100%N); (3) 200 kg urea-N ha−1 and straw (100%N + S); (4) 160 kg urea-N ha−1 (80%N); (5) 160 kg urea-N ha−1 and NI (Nitrapyrin in this study) (80%N + NI); and (6) 160 kg urea-N ha−1, NI, and straw (80%N + NI + S). The results showed that the five N fertilization treatments yielded 16–25% more grain and 39–60% more crop N uptake than the control, but the differences among the five treatments were not statistically significant. Compared with the 100%N, 20% fertilizer-N reduction (80%N) decreased the 15N concentration in topsoil and plant pools but increased the proportion of plant 15N recovery at harvesting (NUE15N, 60% vs. 50%). Compared with the 80%N, NI co-application (80%N + NI) delayed soil nitrification and increased soil 15N retention at harvesting (52% vs. 36%), thereby decreasing NUE15N significantly. Straw incorporation decreased fertilizer-N retention in soil compared with NI co-application because it promoted NUE15N significantly. In conclusion, the results demonstrate that NI and straw additions are efficient strategies for stabilizing fertilizer-N in soils and potentially minimizing N loss; however, their effects on NUE15N vary and the related mechanism must be further clarified in long-term trials.

Evaluating the effects of the CERES-Rice model to simulate upland rice (Oryza sativa L.) yield under different plant density and nitrogen management strategies in Fogera Plain, Northwest Ethiopia

This study assessed the optimal nitrogen (N) fertilizer rate and planting density for the well-adapted upland rice cultivar NERICA_4 on the Fogera Plain. The primary objective was to evaluate the effects of varied planting densities and N-fertilizer rates on upland rice yield and other agronomic parameters. A two-year field study (2020 and 2021) was conducted at the Fogera Rice Research Field Station, testing nine plant densities (75, 87, and 98; 72, 82, and 91; 70, 79, and 89 plants per m2 and two N rates (115 and 138 kg N ha−1). The Crop Simulation Model Crop Environment Resource Synthesis (CSM-CERES-Rice) within the Decision Support System for Agrotechnology Transfer (DSSAT) framework was calibrated and validated using site-specific weather, soil, crop, and agronomic management data from the experiment. Results on the subsequent RMSE, RMSEn, and d index values during the calibration phase were 0.074 t ha−1, 1.82 %, and 0.86 of grain yield; 0.307 t ha−1, 3.36 %, and 0.87 of by-product yield; 0.489 t ha−1, 3.74 %, and 0.79 of top dry biomass yield; and 0.28, 8.24 %, and 0.63 of leaf area index values, respectively. Whereas results on the corresponding RMSE, RMSEn, and d index values during the evaluation phase were: 0.58 t ha−1, 1.33 %, and 0.90 of grain yield; 0.69 t ha−1, 0.58 %, and 0.99 of by-product yield; 0.678 t ha−1, 4.36 %, and 0.67 of top dry biomass yield; and 0.75, 13.92 %, and 0.74 of leaf area index, respectively. The findings of the long-term simulation showed that a 23 % increase in grain yield was achieved with 138 kg N ha−1 and 87 plants per m2 of planting density, as compared to 115 kg N ha−1 and 75 plants per m2 of plant density. The recommended optimum plant density and N fertilizer rate were 138 kg N ha−1 with PD2 of plant density for upland rice production in the Fogera Plain.

Environmental transport of excess nitrogen fertilizer in peach orchard: Evidence arising from 15N tracing trial

In pursuit of high fruit yield, overwhelming amount of nitrogen (N) fertilizer was unreasonably applied in orchard, resulting in lower fertilizer N uptake and higher environmental loss. It is crucial to propose appropriate fertilization timing and optimal N management by clarifying fruit tree N uptake pattern in orchard systems. Here, a 15N isotope enrichment trial was conducted in peach orchard to assess the transport of applied synthesized fertilizer-N to the plant and environment in the Taihu Lake region. Ammonium sulfate ((NH4)2SO4, 10.12 atom % 15N), as the N source, was applied with four split applications at 382.5 kg N ha−1 during one plant growth cycle. Results showed N deriving from fertilizer (NDFF) accounted for 24.5% in leaves and 38.4% in fruits, respectively. During the annual growth cycle, the applied fertilizer-N uptake and utilization was higher in reproductive growth stage than vegetative growth stage. After harvest, 28.8% of applied fertilizer-N was absorbed by peach tree, 9.5% was lost to the environment through surface runoff, ammonia (NH3) volatilization and nitrous oxide (N2O) emission, 29.6% was retained in the 0–160 cm soil profile, the remaining 32.1% was unaccounted N including N leaching and N loss from the N removal progress. Generally, more applied fertilizer-N moved to the environment in high N input peach orchard. In order to promote optimal N management, the applied fertilizer-N rate should be reduced by 30% and emphasized on fertilization at the reproductive growth period according to tree N uptake pattern.

Straw Residual Retention on Wheat Photosynthetic Characteristics, Utilization of Water and Nitrogen, and Reactive Nitrogen Losses

Straw residual retention is an emerging and promoted practice in rain-fed northwest China, but its effect on wheat photosynthetic characteristics, the utilization of water and nitrogen, and reactive nitrogen losses is poorly understood. A two-year consecutive field experiment was conducted to investigate the impacts of residual incorporation into soil and nitrogen application on wheat nitrogen and water utilization, yield and nitrogen losses during 2018–2020. The split-plot design of two tillage systems [conventional tillage (CT), and straw residue incorporated into soil (SR)] and three nitrogen rates [0 kg ha−1 (N0), 144 kg ha−1 (N144), 180 kg ha−1 (N180)] was implemented. Our results demonstrated that compared to CT, SR significantly influenced several key metrics. Compared with CT, SR increased the wheat photosynthetic rate (Pn), transpiration rate (Tr), leaf area index (LAI), leaf total chlorophyll (Chl-total), glutamine synthetase (GS) and nitrate reductase (NR) by an average of 5.38%, 12.75%, 8.21%, 5.79%, 16.21% and 20.08%, respectively (p < 0.05). In addition, SR increased the wheat grain yield and nitrogen uptake accumulation (NUA), evapotranspiration (ET), precipitation storage efficiency (PSE), and mineral nitrogen residual after harvest (except for SR-N180 in 2019–2020), but decreased the apparent nitrogen recovery when compared with CT. However, there was an insignificant difference in the ammonia (NH3) volatilization and nitrous oxide (N2O) emissions of SR and CT. With an increase in the N-fertilization rate, the Pn and Tr, NH3 volatilization, N2O emission, mineral nitrogen residual (except for SR-N180 in 2019–2020), LAI, Chl-total (except for SR-N180 and CT-N180 in 2018–2019), GS, NR, grain yield, WUE, and NUA increased significantly; however, the ET, PSE, apparent nitrogen recovery (ANR), and nitrogen harvest index (NHI) decreased significantly. Furthermore, the differences between N144 and N180 in terms of the photosynthetic characteristics of wheat, the utilization of water and nitrogen, and yield were not significant. Overall, straw retention with N144 could be recommended as a resource-saving and environment-friendly management practice in a rain-fed winter wheat–fallow cropping system in northwest China.

Towards a cost-effective framework for estimating soil nitrogen pools using pedotransfer functions and machine learning

Globally, the strategic use of nitrogen (N) is important in optimizing economic returns and reducing soil nitrogen losses to the environment. Incorporating reliable estimates of nitrogen (N) mineralized over a growing season (GSN) into N-fertilizer rate prescriptions is critical, but may often lack a direct measurement. For this purpose, Pedotransfer functions (PTFs) of total nitrogen (TN) – representing the stable pool from which N is mineralized and biological nitrogen availability (BNA) – representing the labile pool of N mineralization were used to estimate GSN. GSN was calculated based on TN and BNA results from a soil health database (SHD), which also includes a suite of related soil health parameters (n = 2222). Using a process of recursive feature elimination (RFE) and cost-benefit feature elimination (CBFE), the best predictors of TN, BNA, and GSN were identified using a suite of machine learners (MLs) and regression analysis. For TN, RFE revealed that BNA, active carbon (AC), sand (Sa), and soil organic matter (OM) were the best predictors yielding a Lin’s concordance correlation coefficient (CCC) of 0.80 and a reduction in theoretical cost of 41 % compared to the control. CBFE resulted in AC, soil respiration (SR), clay, Sa, and OM as the most cost-effective predictors of TN with a CCC of 0.79 and a theoretical cost savings 49 % below the cost of using all appropriate soil health parameters in the SHD. With respect to BNA, the best predictors from RFE were aggregate stability (AS), AC, SR, and TN with a CCC of 0.78 and a theoretical cost reduction of 23 %. CBFE retained AC, SR, S, TN, OM and pH as predictors of BNA with a CCC of 0.78 and reduction of 29 % in theoretical cost. Finally, GSN results from RFE identified AS, AC, SR, OM and pH as the best predictors with a 0.82 CCC and 17 % reduction in theoretical cost. CBFE, on the other hand, identified AC, SR, sand, OM, and pH as the most cost-efficient predictors while maintaining a CCC of 0.82 and theoretical cost reduction of 29 %. Of the MLs used for pattern recognition (i.e., cubist, random forest, support vector machine, and stochastic gradient boosting), cubist model outperformed the others for the majority of iterations of the RFE and CBFE processes. The cost-effective framework, and the N-related PTFs developed in this study will greatly enhance our ability to predict of soil N-pool dynamics and the ability to incorporate GSN estimates into N-fertilizer recommendations for producers worldwide. Improvements in predictive strength could be achieved by incorporating climate and soil management practices into PTF development. Another area for improvement and future study would include addition of spatial and landscape variability related to N-measures via digital soil mapping applications.

Effect of the pre-magnetic treatment of seeds and the N-fertilizer on the yield and quality of groundnut grown in sandy soil

<p>This field trial aimed to study the effect of the magnetic treatment (MT) of urea as a nitrogen (N) fertilizer as well as the MT of the groundnut (<em>Arachis<strong> </strong>hypogaea </em>L.) seeds before sowing on the crop yield and quality under sandy soil conditions during the summer seasons of 2020 and/or 2021. Treatments were distributed in a split-plots design in triplicates. The control CL has received the recommended dose RD of the N-fertilizer while other treatments received the rates 50, 75, and 100% of the RD as magnetized urea (main factor F1) applied to the surface soil. The sub-factor (F2) was the time of MT (15, 30, and 45 min) of the groundnut seeds exposed to magnetic field MF 1.4 T before planting. Representative samples from the soil and plant were taken after harvesting. At the 15-min time and 100% N-fertilization, the yield of pods and seeds (kg ha<sup>-1</sup>) has increased relatively by 8.2% and 9.7% respectively, compared to the corresponding CL. At the 30-min time and 50% and 100% N-fertilization, the yield (kg ha<sup>-1</sup>) has increased relatively by 9.7% and 13.3% respectively for pods and by 10.1% and 16.8% respectively for the seeds. At the 45-min time and 50% N-fertilization, the yield (kg ha<sup>-1</sup>) has increased by 12.4% and 14.6% for pods and seeds, respectively. The 100% N-fertilization along with 15 min MT before cultivation or the 50% and/or 100% N-fertilization along with 30 min MT or the 50% along with 45 min MT could be recommended. The agronomic efficiency (AE) for the N, P, and K nutrients was increased by the MT in the order 15 min < 30 min < 45 min at the 50, 75, and 100% N-fertilization rates.</p>

Impact of Rice–Wheat Straw Incorporation and Varying Nitrogen Fertilizer Rates on Soil Physicochemical Properties and Wheat Grain Yield

Straw return (SR) is crucial for the comprehensive and efficient utilization of resources within agroecosystems; however, its impact on soils and wheat grain yield in the Jianghan Plain of the Yangtze River Basin, Hubei Province of China, is not fully known. Therefore, the present study was undertaken to assess the impact of returning rice–wheat straw, along with different nitrogen (N) fertilizer applications, on soil physicochemical properties and wheat grain yield. The Yangmai 23 wheat variety was cultivated in the Experimental Farms of Yangtze University in the Yangtze River Basin, with three rates of rice SR (0, 50 and 100%) and four N fertilizer rates (0, 33.3, 70 and 100%) with 180 kg/ha urea. The integrated use of SR- and N-fertilizer rates significantly altered soil nitrogen, nitrate, ammonium, phosphorus, potassium, pH and moisture within the 20 cm depth before the seeding, jointing and maturation stages of the wheat. The grain yields of 6408 ± 110 − 8290.00 ± 298 and 4726 ± 62 − 6758.00 ± 196 kg/ha were obtained in the 2021–2022 and 2022–2023 seasons, respectively. The studied soil physicochemical properties either before seeding, or at the jointing and maturation stages had a significant effect on final grain yield. These results underscore the combined effect of SR- and N-fertilizer application to improve wheat productivity in the Yangtze River Basin. However, further studies are ongoing to assess the impact of these treatments on the soil microbial community, as well as on wheat grain quality.

Effects of Different Irrigation Levels and Fertilizer Rates on Yield, Yield Components and Water Productivity of Onion at Adami Tulu Agricultural Research Center

Today’s agriculture sector faces a complex series of challenges to cope with the demands for sustainable management and production, which entails an increase in food production to ensure food security while using less water per unit of output and reducing nitrogen (N) fertilizer losses through leaching. The experiment was conducted at Adami Tulu Agricultural Research Center on-station to study the effect of different irrigation levels and N-fertilizer rates on plant height, bulb yield, bulb diameter, and bulb height and water productivity of onion. The treatments of the experiment had factorial combinations of three levels of watering and four N-fertilizer amounts. Results indicated that the highest plant height (53.07 cm), bulb height (6.13 cm), bulb diameter (6.21 cm), marketable bulb yield (241.39 qt/ha) and total bulb yield (252.89 qt/ha) were obtained from full irrigation and fully N-fertilized compared to the deficit conditions. The highest water productivity was recorded from 60% ETc irrigation level and 150 Kg/ha N-fertilizer application rate, but the reduction in water productivity with 80% ETc and 150 Kg/ha N-fertilizer application rate was not significant. Hence, if water is not limiting factor, 100% ETc irrigation level and 150 Kg/ha N-fertilizer could be suggested to apply. But if water becomes 232 limiting factor, 80% ETc irrigation level with 150 Kg/ha N-fertilizer would be more appropriate for growing onion in the study area. Therefore these can be used as one package of onion production technology and all growers better to apply.

Effect of Irrigation Water Level and N-fertilizer Rate on Yield and Water Productivity of Wheat Under Furrow Irrigation at Tibila Irrigation Scheme, Arsi Ethiopia

Effect of Irrigation Water Level and N-fertilizer Rate on Yield and Water Productivity of Wheat Under Furrow Irrigation at Tibila Irrigation Scheme, Arsi Ethiopia

Optimized number of suction cups required to predict annual nitrate leaching under varying conditions in Denmark

Nitrate concentrations in soil water leaving the root zone measured by suction cups combined with water transport modeling is a commonly used practice in Denmark for calculating nitrate leaching. Two suction cups installed in one plot giving one water sample and replicated four times, (eight total suction cups) to reduce variability between samples. For practical reasons, it would be beneficial to minimize the number of suction cups used yet maintain reliable predictions. To assess the variability in reducing suction replicates, this study analyzed data from five research sites across Denmark representing annual field nitrate leaching predictions for different combinations of soil, weather conditions, crops, N-fertilizer rates, and winter soil cover, covering a total of 173 annual nitrate leaching experiments. The analysis was conducted having different nitrate leaching predictions using different numbers of replicates of suction cup measurements. Linear regression was used to identify the different influences of leaching year (hydrological year), N rate applied, soil characteristics, and crop sequence on nitrate leaching. The analyses were set up on three 2-yr and two 3-yr field experiments in five different sites. Crop effects showed that cereals and winter cover sown in autumn 2017 had significantly more nitrate leaching than in 2015 and 2016 leaching years due to high precipitation rates in the autumn. Furthermore, decreasing the number of suction cup replicates from four (eight total) to three replicates (six total) did not have a significant effect on nitrate leaching prediction. In contrast, decreasing replicates from four to two (four total) and one (two total) replicates did show a significant difference. Therefore, using three replicates is a viable solution for future sampling strategies and a good trade-off between costs and accuracy.

Changes in the Microbial Community in Maize (Zea mays L.) Root Spatial Structure Following Short-Term Nitrogen Application.

The beneficial interactions between crop roots and microbiomes play a key role in crop nutrient availability, growth promotion, and disease suppression. Recent research, however, rarely reported the effects of nitrogen (N) application rate on microbial community composition at different spatial structures in the maize root zone. Therefore, one experiment was conducted to examine the influence of three N-application levels (0, 180, and 360 kg N ha-1) on microbial community composition in three root-associated compartments of maize (bulk soil, rhizoplane, and endosphere). The microbial diversity and community composition differed significantly among the various compartments. The effects of N application on fungal composition decreased in the order bulk soil > rhizosphere > endosphere at different sampling positions. Also, the fungal composition was more sensitive to the N-fertilizer rate in the bulk soil and the rhizosphere than the bacterial community. A total of 14.42, 9.46, and 3.55% of all taxonomic groups were sensitive to N fertilizer, respectively. The keystone species fungal groups were Humicola (bulk soil), Gibberella (rhizosphere soil), and Humicola (endosphere). Together, our results demonstrate that compared with that of the bacterial community, the fungal community composition was more susceptible to different N-application rates. N fertilization affected the distribution of microflora by changing soil physicochemical properties and enzyme activities. There were strong correlations between microbial communities in maize under the N180 treatment. Moreover, the N180 treatment had the maximum fresh yield and biomass at 64.5 and 24.3 kg·ha-1, respectively.

Predicted Soil Greenhouse Gas Emissions from Climate × Management Interactions in Temperate Grassland

Grassland management practices and their interactions with climatic variables have significant impacts on soil greenhouse gas (GHG) emissions. Mathematical models can be used to simulate the impacts of management and potential changes in climate beyond the temporal extent of short-term field experiments. In this study, field measurements of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) emissions from grassland soils were used to test and validate the DNDC (DeNitrification-DeComposition) model. The model was then applied to predict changes in GHG emissions due to interactions between climate warming and grassland management in a 30-year simulation. Sensitivity analysis showed that the DNDC model was susceptible to changes in temperature, rainfall, soil carbon and N-fertiliser rate for predicting N2O and CO2 emissions, but not for net CH4 emissions. Validation of the model suggests that N2O emissions were well described by N-fertilised treatments (relative variation of 2%), while non-fertilised treatments showed higher variations between measured and simulated values (relative variation of 26%). CO2 emissions (plant and soil respiration) were well described by the model prior to hay meadow cutting but afterwards measured emissions were higher than those simulated. Emissions of CH4 were on average negative and largely negligible for both simulated and measured values. Long-term scenario projections suggest that net GHG emissions would increase over time under all treatments and interactions. Overall, this study confirms that GHG emissions from intensively managed, fertilised grasslands are at greater risk of being amplified through climate warming, and represent a greater risk of climate feedbacks.

Climate risk management for the rainfed rice yield in Lao PDR using APCC MME seasonal forecasts

The tailored process-based crop model equipped with seasonal climate forecasts have been a useful tool for managing agricultural risks from climatic variability. In this study, we provided a risk management framework for a rainfed paddy rice field in Savannakhet province of Lao People's Democratic Republic (PDR) that allows achieving the national target yield (5.0Mg ha-1) under climatic uncertainty. We collected the multi-model ensemble (MME) tercile hindcasts of 3-month (September to November, SON) and 5-month (July to November, JASON) rainfall for 1991–2010 from the international collaborative archive of the APEC Climate Center (APCC). The monthly probabilistic hindcasts were temporally downscaled by a stochastic weather generator to daily meteorological inputs for the CERES-Rice crop model. Then, the lowland rainfed rice yields at the field scale were simulated by the process-based crop model with different nitrogen (N) fertilizing strategies, and compared the outcomes against the observed rice yields. The results showed that the simulated rice yields from the 3-month hindcasts with the N-fertilizer application rate of level 1 (60 kg ha-1) were closer to the observed than those from the 5-month hindcasts. About 3.05Mg ha-1 of rice yields were estimated under the 3-month seasonal forecasts in 2020 with the N-fertilizer application rate. We found that additional 40 kg ha-1 of N-fertilizer rate may be required to achieve the national target rice yield (5.0Mg ha-1) under climatic uncertainty conditioned by the seasonal forecasts. We also suggest that the proposed crop modeling approach underpinned by seasonal climate forecasts can be useful to reduce impacts of climate variability on rice yield by providing various agricultural management practices.

Fate of each period fertilizer N in Mollisols under water and N management: A 15N tracer study

For soil-crop systems, it is important to increase the retention of fertilizer N that is not effectively utilized by crops in stable forms in soil and reduce fertilizer N loss from agroecosystems through agricultural practices. However, it remains obscure how the fate of fertilizer N will be affected by water and N management. To further clarify the effects of water and N management on the fate of each period fertilizer N and residual fertilizer N amounts of different derived forms, a field experiment was conducted in Mollisols in Northeast China. This experiment combined a field plot experiment with a flied microplot 15N isotope experiment, and six treatments were performed: two irrigation management modes (controlled irrigation and flooded irrigation) and three fertilizer-N rates (85, 110 and 135 kg/ha). Additionally, the basal, tillering, and panicle fertilizer N were tracked by 15N-labeled urea to study the fate of each period fertilizer N. The present study showed that under controlled irrigation (CI), fertilizer-derived N in different forms increased with the increase N rate. Under flooded irrigation (FI), with the increase N rate, the residual organic nitrogen (NO) first increased and then decreased, and the other forms of fertilizer-derived N increased. In the total residual fertilizer N in soil, residual basal fertilizer N accounted for the highest proportion under the two irrigation modes, residual tillering fertilizer N accounted for the lowest proportion under FI, and panicle fertilizer N accounted for the lowest proportion under CI. NO accounted for the highest proportion of the residual amount of each period fertilizer N under CI and FI, while NO3--N accounted for the lowest proportion under CI, and fixed ammonium accounted for the lowest proportion under FI. Compared with FI, CI increased the total residual fertilizer N amount and promoted the conversion of residual fertilizer N into NO. The present study suggested that CI, as a water-saving irrigation mode, not only decreased agricultural water consumption but also increased fertilizer N retention in soil and enhanced the conversion of residual fertilizer N into NO. The establishment of appropriate water and N management has great potential for the regulation of residual fertilizer N in paddy soil.

Growth and Yield Responses of Hot Pepper to Nitrogen Fertilisation in Jos-Plateau, Nigeria

The production of pepper in Nigeria has raised the living standards of many smallholder farmers. The productivity of yellow and red pods is generally low due to poor agronomic practice. There is the need to help smallholder farmers to achieve sustainable production in order to improve and secure their livelihood. This study was aimed to investigate the effects of the rate of Nitrogen fertilisation on growth and yield of pepper in the Jos-Plateau environment. The experiment was 3 x 6 factorial, comprising three varieties of pepper and six levels of N-fertilizer. The treatmentcombinations were laid out in the field using the randomised complete block design. Plant height, number of leaves, number of branches, relative growth rate and days to 50% flowering were higher in the variety F BT than in the other varieties. Leaf area index, length of fruit and fresh fruit 1 yield were higher in the variety SAFI than in the other varieties. Fruit width and the mean weight of fruit were higher in the Miango Local than in the other varieties. The application of N-fertilizer up to 150 kgN ha-1 resulted in significantly higher values in most of the parameters studied. Significant interactions of N-fertilizer rate and variety on plant height, number of leaves per plant, number of branches per plant, leaf area index, relative growth rate, mean weight of fruit and fresh fruit yield were observed. The study recommends the application of N-fertilizer up to 150 kgN ha-1 for cultivation of pepper in the Jos-Plateau environment.

Synchronizing Nitrogen Fertilization and Planting Date to Improve Resource Use Efficiency, Productivity, and Profitability of Upland Rice.

Synchronizing nitrogen (N) fertilization with planting date (PD) could enhance resource use efficiency and profitability of upland rice (Oryza sativa L.) production in Thailand. The objective of the study was to assess upland rice responses to four N fertilization rates (NFRs) and three planting dates. Field experiments were conducted during two growing seasons under four NFRs, no N applied (N0), 30 (N30), 60 (N60), and 90 kg N ha−1 (N90), and NFR were applied at the initiation of tillering and panicle emergence stages. The planting dates selected were early (PD1), intermedium (PD2), and late planting (PD3) between September and December of each season. The NFRs and planting dates had a significant influence on N uptake, N use efficiency (NUE), crop water productivity, yield and yield attributes, and profitability of upland rice production. A linear relationship among NFRs, agronomic traits of upland rice, N uptake, and crop water productivity was observed, and a significant seasonal effect was indicated. Fertilization at N90 under PD2 enhanced yields, yield attributes, and grain yields, as well as crop water productivity by 56 and 105% during the second and first seasons, respectively. Grain N, total N, and straw N were increased by 159, 159, and 160%, and by 90, 114, and 153%, during the first and second seasons, respectively. Enhanced N efficiencies, including agronomic efficiency, recovery efficiency, partial factor productivity, and N harvest index, at varying NFRs were observed under PD2 during both seasons. Highly significant (p < 0.001) and positive associations were observed among agronomic attributes, N uptake, NUE, and crop water productivity of upland rice in correlation assessment. Profitability from grain yields was observed with N fertilization and N90 resulted in maximum profit under all the PDs. However, the highest marginal benefit-cost ratio was observed at N60 under PD2 during both seasons. The results suggest that the NFR of 90 kg N ha−1 and planting at the end of September or start of October would enhance resource use efficiency and productivity, and maximize profitability. Furthermore, long–term field investigations with a range of NFRs and adopting forecasting measures to adjust the planting date for upland rice are recommended.

Adopting different irrigation and nitrogen management based on precipitation year types balances winter wheat yields and greenhouse gas emissions

The implementation of appropriate irrigation and nitrogen (N) measures is essential for obtaining higher grain yields while minimizing environmental risks. To determine whether deficit irrigation combined with reduced N-fertilizer rate can mitigate greenhouse gas (GHG) emissions and maintain yield under different precipitation year types (wet, normal, and dry years), a six-year (2014–2020) field experiment was conducted in the North China Plain during the winter wheat growing seasons. There were two irrigation schedules (conventional irrigation, W2; deficit irrigation, W1) and two levels of N application (conventional fertilization, N2; nitrogen reduction, N1), which resulted in four treatments: W2N2, W2N1, W1N2, and W1N1. Irrigation, fertilization, and precipitation year types all affected the GHG emissions and yield of winter wheat. Compared with conventional irrigation and nitrogen management (W2N2 treatment), appropriate nitrogen reduction (W2N1) and deficit irrigation (W1N2) decreased CO 2 emissions by 17.7–19.8% and 14.8–25.2%, respectively, and reduced N 2 O by 34.4–36.3% and 21.0–25.8%, respectively. Without compromising crop yield, the W1N2 treatment with deficit irrigation resulted in 17.1% lower net greenhouse gas (NGHG) and 16.5% lower greenhouse gas intensity (GHGI) in wet years; and the W2N1 treatment with nitrogen reduction reduced NGHG and GHGI by 20.5% and 18.7%, respectively, in normal years; and it also led NGHG and GHGI to decrease by 18.5% and 18.1%, respectively, in the dry year. Therefore, deficit irrigation in wet years and N reduction in normal years and dry year can reduce GHG emissions and maintain yield. Optimizing N fertilizer and irrigation management according to variation in precipitation conditions can mitigate GHG emissions, enhance yield, and promote the sustainable development of agriculture and the environment. • Greenhouse gas emissions significantly differed among different precipitation year types in a six-year field experiment. • In wet years, deficit irrigation reduced net greenhouse gas by 17.0% and maintained wheat production. • Nitrogen reduction decreased net greenhouse gas by 20.5% and 18.5% in normal and dry years, respectively. • Optimized water and fertilizer management schemes for winter wheat in different precipitation year types were proposed.