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Abstract The effects of different nitrogen (N) application levels on seed endophytes and grain nutritional quality are not yet clear. The impact of four N application levels on endophytes and amino acid accumulation in purple rice seeds was examined using 16S rRNA and ITS amplicon sequencing technology. This study integrates 16S rRNA, ITS amplicon sequencing technology and amino acid‐targeted detection to explore the effects of four different nitrogen application levels (0 kg hm−2, Y1N0; 180 kg hm−2, Y1N1; 270 kg hm−2, Y1N2; 360 kg hm−2, Y1N3) on the accumulation of endophytic bacteria, fungi and amino acid content in purple rice seeds and their interaction mechanisms. The findings indicated an increase in the contents of most amino acids with increasing N application. The dominant bacterial species in the community were mainly from the phyla Proteobacteria and Actinobacteriota, while the dominant fungal species were from the phyla Ascomycota and Basidiomycota. There was a significant difference in the richness of endophytic fungal communities between Y1N0 and Y1N2. Y1N1 showed significant differences in Mucoromycota compared to Y1N3. The quantity of operational taxonomic units (OTUs) in the bacterial and fungal community co‐occurrence network increased with increasing N fertilizer, showing strong correlations with Sporidiobolus, Chaetomium, Humicola, Botryotrichum, Ophiosphaeria and Dioszegia for most amino acids. These findings indicate that a high amount of N fertilizer greatly increases amino acid contents in purple rice seeds and improves the diversity and stability of endophytic fungal populations.

Abstract This study aims to explore the formation mechanism of starch structure and the relationships between the appearance quality and starch structure of soft rice under different nitrogen levels. We comprehensively investigated the physiological aspects, starch structure variations, and appearance quality of soft rice in response to different nitrogen applications. The results showed that under the moderate nitrogen application (270 N), the soft rice exhibited the highest AGPase activity, the highest large‐starch granule content, and the lowest chalkiness. Under the highest nitrogen application (360 N), the soft rice exhibited the highest GBSS and DBE activity and the lowest SBE activity, the highest content of long‐branched amylopectin, the lowest relative crystallinity, the fewest ordered structures, the most amorphous structures, the largest semi‐crystalline lamellar thicknesses, and the highest transparency of chalk‐free rice. In conclusion, moderate nitrogen fertilization (270 N) improved the AGPase activity, which leaded to fuller starch granules and more compact endosperm in soft rice. Thus, the grain chalkiness of soft rice decreased. Continuous nitrogen application (0‐360 N) constantly increased the GBSS and DBE activity and reduced the SBE activity in soft rice, leading a lower content of short‐branched amylopectin and a higher content of long‐branched amylopectin in soft rice. Thus, the relative crystallinity and ordered structures of soft rice were reduced. These structures improved the transparency phenotype of soft rice.

Abstract In Senegal, agriculture is an important sector underpinning the socioeconomic fabric of the populace. Notably, the agricultural production in this region exhibits heightened sensitivity to climatic perturbations, particularly droughts and heat waves. This study aims to determine the resilience of different agronomic interventions for farmers practicing mixed farming that produce both crops (i.e., groundnut (Arachis hypogaea L.) and pearl millet (Pennisetum glaucum (L.) R. Br.)) and raise animals in the Groundnut Basin in Senegal, which holds historical and socioeconomic significance. To understand the current situation regarding demographics, economics, consumption behavior, and farm operations for smallholder farmers, data were comprehensively collected from government and nongovernment organizations (NGO) reports, scientific papers, organization databases, and surveys. Additionally, the Agricultural Production Systems sIMulator (APSIM) was used to understand how combinations of three planting dates, three plant densities, and six urea nitrogen (N) fertilizer rates affected the yield of pearl millet, which were used as the alternative scenarios to the baseline in the farm modeling and analyses. All the collected and generated data were used as inputs into the Farm Simulation Model (FARMSIM) to generate economic, nutritional, and risk data associated with mixed farming systems. The generated data were then used to determine the resilience of the alternative scenarios against the baseline. Initially, a multi‐objective optimization was employed to meet nutritional needs while maintaining a healthy diet at the lowest cost. Then, the scenarios that met the population's nutritional requirements were evaluated based on four economic indicators: net cash farm income (NCFI), ending cash reserves (EC), net present value (NPV), and internal rate of return (IRR). Lastly, those that passed the economic feasibility test were ranked based on risk criteria certainty equivalent (CE) and risk premium (RP). The analyses found N fertilizer rates of 0, 20, and 100 kg N ha−1 were generally economically not feasible. Additionally, medium (early‐July to late‐August) and late (late‐July to mid‐September) planting dates generally performed better than early (early‐June to late‐July) planting dates, while plant densities of 3.3 and 6.6 pL m−2 performed better than 1.1. The robust resilience approach introduced in this study is easily transferable to other regions.

Abstract Biochar is promoted as a means of improving soil fertility. Yet, few experiments have investigated its potential to improve nitrogen (N) use efficiency for high‐yielding maize production in the U.S. Midwest. We tested the hypothesis that biochar application increases inorganic soil N availability during maize growth, leading to higher grain yields and N recovery efficiency while reducing the risk of N leaching following harvest. Four N fertilizer rates (0, 90, 179, and 269 kg ha−1 as urea ammonium nitrate [UAN] solution) were applied with or without biochar (10 Mg ha−1) before planting in a two‐year field study. Inorganic soil N concentration was measured during the growing season (0–15 cm), and deep soil cores were obtained following harvest (0–90 cm). Results show that biochar did not affect maize yield, crop N uptake, or N recovery efficiency (by the difference method) across N rates, and there was no biochar by N rate interaction. While biochar lowered soil inorganic N concentrations on several sampling dates, this did not translate into seasonal differences in cumulative soil N availability, although grain yields in the unfertilized control were ~10% lower with biochar, suggesting net N immobilization. Biochar partially reduced the risk of N leaching following harvest by decreasing soil N concentrations at 30–60 cm, but mean concentrations for 0–90 cm were not different. Compared to previous work highlighting the benefits of biochar in arid climates with low soil fertility, we found no evidence of increased crop yield, NRE, or reduced risk of N leaching on Mollisols in a temperate climate.

Abstract Biochar can significantly change soil properties and improve soil quality. However, the effects of long‐term combined application of biochar (B) and nitrogen (N) fertilizer on relationships between soil enzyme activity, microbial community structure, and crop yield are still obscure. We characterized these relationships in a long‐term (8 years) field experiment with rice, two biochar rates of 0 and 13.5 t ha−1 year−1 (B0 and B) and two N fertilizer rates of 0 and 300 kg N ha−1 year−1 (N0 and N). The repeated, long‐term combined applications of biochar and N fertilizer significantly increased microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN), but biochar decreased the abundance of total bacteria, fungi, actinomycetes, and gram‐positive and gram‐negative bacteria as well as the amount of total phospholipid fatty acids. The activity of leucine aminopeptidase (LAP) decreased significantly in the biochar‐amended and N fertilized treatment, but the LAP activity either remained unchanged or increased with biochar amendment at N0. The relative abundance of bacterial phylum Chloroflexi was increased in the combined biochar and N fertilizer treatment. The changes in soil organic matter and the activity of α‐1,4‐xylosidase were the major properties influencing soil bacterial community composition, whereas the structure of fungal community was governed by MBC, MBN, and LAP activities. In addition, long‐term biochar and N fertilizer applied together significantly increased rice yield (more than biochar and nitrogen fertilizer applied alone). Yield was significantly positively correlated with LAP activity, but significantly negatively correlated with the relative abundance of Chloroflexi. In conclusion, long‐term biochar and nitrogen fertilizer applications increased rice yield, which was associated with altered soil microbial community and enhanced activity of some enzymes.

Nitrogen (N) content affects aboveground maize growth and nutrient absorption by altering the belowground rhizospheric ecosystem, impacting both yield and quality. However, the mechanisms through which different N supply methods (chemical and biological N supplies) regulate the belowground rhizospheric ecosystem to enhance maize yield remain unclear. To address this issue, we conducted a field experiment in northeast China, comprising three treatments: maize monocropping without N fertilizer application (MM), maize/alfalfa intercropping without N fertilizer application (BNF), and maize monocropping with N fertilizer application (CNS). The MM treatment represents the control, while the BNF treatment represents the biological N supply form, and CNS treatment represents the chemical N supply form. In the autumn of 2019, samples of maize and rhizospheric soil were collected to assess parameters including yield, rhizospheric soil characteristics, and microbial indicators. Both BNF and MM significantly increased maize yield and different yield components compared with MM, with no statistically significant difference in total yield between BNF and CNS. Furthermore, BNF significantly improved N by 12.61% and available N (AN) by 13.20% compared with MM. Furthermore, BNF treatment also significantly increased the Shannon index by 1.90%, while the CNS treatment significantly increased the Chao1 index by 28.1% and ACE index by 29.49%, with no significant difference between CNS and BNF. However, CNS had a more pronounced impact on structure of the rhizosphere soil bacterial community compared to BNF, inducing more significant fluctuations within the microbial network (modularity index and negative cohesion index). Regarding N transformation pathways predicted by bacterial functions, BNF significantly increased the N fixation pathway, while CNS significantly increased assimilatory nitrate reduction. In CNS, AN, NO 3 -N, NH 4 -N, assimilatory nitrate reduction, and community structure contributed significantly to maize yield, whereas in BNF, N fixation, community structure, community stability, NO 3 -N, and NH 4 -N played significant roles in enhancing maize yield. While CNS and BNF can achieve comparable maize yields in practical agricultural production, they have significantly different impacts on the belowground rhizosphere ecosystem, leading to different mechanisms of yield enhancement., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

Abstract Hybrid rice has been planted throughout China to ensure food security owing to its higher yield potential than inbred rice. Meanwhile, substantial nitrogen (N) fertilizer has been applied to feed hybrid varieties for maximizing grain yield. However, to what extent the higher yield of hybrid than inbred rice depends on N fertilizer input remains unclear. A meta‐analysis was conducted in this study to (1) quantify the difference in N uptake and utilization between hybrid and inbred rice; (2) determine whether hybrid rice requires more N than inbred rice for producing per unit grain yield; and (3) evaluate the impact of the difference in crop growth duration between hybrid and inbred rice on their yield performance. The results showed that, overall, hybrid rice achieved a 10.1% higher grain yield, and 9.7% higher daily grain yield than inbred rice. This grain yield advantage increased from 6.1% to 11.9% depending on whether hybrids have longer crop growth duration than inbred rice. The yield advantage of hybrid rice was explained by higher total N uptake and internal N use efficiency, but not explained by N fertilizer input. Moreover, the yield advantage of hybrid rice with N fertilizer was driven by higher yield without N fertilizer instead of yield response to N fertilizer. These results suggest that hybrid rice does not necessarily require more N fertilizer to achieve higher yield than inbred rice. Therefore, hybrid rice could be planted with fewer external N to ensure food security and reduce environmental costs.

Abstract Cellulosic biofuel from forest thinning operations is a potential renewable energy source in regions with overstocked forests such as those in western United States. However, it is possible that biomass removal can deplete nutrients from soil, which can alter soil respiration (Rs) and exoenzyme properties, and potentially impact tree growth. This study evaluates the impact of biomass removal on Rs and exoenzyme properties and the capacity of soil amendments to counteract any potential effects. At two study locations, we created four post‐thinning biomass retention levels: full biomass removal (0×), full biomass retention (1×), double biomass retention (2×), and a no‐thin treatment. Four soil amendment treatments were applied to each biomass retention level: N fertilizer (F), biochar (B), fertilizer plus biochar (FB), and an untreated control (C). We evaluated treatment effects on Rs and activity of four exoenzymes to represent C‐cycling, N‐release, and P‐release processes. Biomass retention levels had no effect on Rs (p = .42) or exoenzyme activities (p > .29). Variation in exoenzyme activity was explained by location, season, soil organic matter, soil moisture content, and temperature. Variation in Rs was explained by the same variables, in addition to C‐cycling exoenzyme activity and soil pH. Soil amendments had no effect on exoenzyme activities (p > .49), and no main effect on Rs (p = .48), though amendments influenced Rs differently at each location (p = .02). Short‐term findings suggest small‐diameter biomass removal for cellulosic biofuel production will not impact Rs and exoenzyme properties, and paired with our tree growth study, provide evidence that biofuel systems are a feasible renewable energy source in the western North America.

Abstract A continuous rise in the global demand for palm oil has resulted in the large‐scale expansion of oil palm plantations and generated environmental controversy. Efforts to increase the sustainability of oil palm cultivation include the recycling of oil mill and pruning residues in the field, but this may increase soil methane (CH4) emissions. This study reports the results of yearlong field‐based measurements of soil nitrous oxide (N2O) and CH4 emissions from commercial plantations in North Sumatra, Indonesia. One experiment investigated the effects of soil‐water saturation on N2O and CH4 emissions from inorganic fertilizers and organic amendments by simulating 25 mm rainfall per day for 21 days. Three additional experiments focused on emissions from (a) inorganic fertilizer (urea), (b) combination of enriched mulch with urea and (c) organic amendments (empty fruit bunches, enriched mulch and pruned oil palm fronds) applied in different doses and spatial layouts (placed in inter‐row zones, piles, patches or bands) for a full year. The higher dose of urea led to a significantly higher N2O emissions with the emission factors ranging from 2.4% to 2.7% in the long‐term experiment, which is considerably higher than the IPCC standard of 1%. Organic amendments were a significant source of both N2O and CH4 emissions, but N2O emissions from organic amendments were 66%–86% lower than those from inorganic fertilizers. Organic amendments applied in piles emitted 63% and 71% more N2O and CH4, respectively, than when spread out. With twice the dose of organic amendments, cumulative emissions were up to three times greater. The (simulated) rainwater experiment showed that the increase in precipitation led to a significant increase in N2O emissions significantly, suggesting that the time of fertilization is a critical management option for reducing emissions. The results from this study could therefore help guide residue and nutrient management practices to reduce emissions while ensuring better nutrient recycling for sustainable oil palm production systems.