Field Crops Research最新文献

Purpose

Substituting chemical fertilizers with biogas digestate can mitigate the negative impacts of fertilizers on soil quality to promote the recycling of livestock manure. This study aims to evaluate the effects of chicken manure biogas digestate as a replacement for chemical fertilizers in rice cultivation, assessing soil nutrients dynamics, bacterial communities, nitrogen (N) metabolism enzyme activity, and rice growth.

Methods

In this study, six treatments were established: no fertilizer (CK), conventional fertilization (CF), and varying proportions of biogas digestate and other N substitution fertilizers (25 %, 50 %, 75 %, and 100 %TP). A three-year field experiment was conducted to evaluate soil nutrient levels, bacterial community abundance, N functional gene expression, rice growth conditions, and N metabolism enzyme activities using standard physical and chemical methods, high-throughput sequencing, and enzyme activity assays.

Results

Our experimental results showed that biogas digestate application promoted rice growth, while the higher biogas digestate doses increased the leaf chlorophyll SPAD values and delayed rice maturity. Compared to the CF treatment, the 75 % TP treatment significantly enhanced rice yield and economic returns. Biogas digestate increased the activities of nitrate reductase (NTR), glutamate synthase (GTS), glutamine synthetase (GLS), glutamic oxalacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) in rice leaves and grains, leading to the higher amino acid and soluble protein contents in the grains. Compared to the CK treatment, biogas digestate application increased soil pH, soil organic matter, alkaline N, available phosphorus, and available potassium by 22.14 %, 37.04 %, 39.38 %, and 39.40 %, respectively. It also enhanced the levels of nitrate N, ammonium N, and soluble organic N in soil. Furthermore, biogas digestate application significantly (p < 0.05) improved soil bacterial community diversity and stability, as well as the abundance of N metabolism functional genes.

Conclusions

Our findings suggest that substituting 75 % of chemical fertilizers with biogas digestate can serve as an optimal application rate for rice cultivation. This application in paddy field does not only reduce chemical fertilizer usage but also enhance soil nutrient content and microbial diversity. It further promotes rice growth and N metabolism enzyme activity, benefiting the increase of both rice yield and quality.

Conventionally, split nitrogen (N) applications at tillering and stem elongation enhance winter wheat yield, protein content, and nitrogen use efficiency. Vegetation indices, such as the Normalized Difference Vegetation Index (NDVI), Normalized Difference Red Edge index (NDRE), and leaf chlorophyll content (LCC) can be used as crop N status indicators (CNSIs) to easily underline the N deficiency. The aim of this study, conducted across 4 growing seasons in North-West Italy, was to create a model for regulating wheat fertilization rates and improve crop yield. The model relies on CNSIs measurements collected during the initial stages of stem elongation, aiming to achieve predetermined yield targets. In each year, the experimental design was a factorial combination of four N rates (0, 33, 66, and 99 kg N ha⁻¹) at tillering and five at stem elongations (0, 33, 66, 99 and 132 kg N ha⁻¹). The Aubusson cultivar, characterized by intermediate yield potential and protein content, was used to calibrate and validate the model in a 3-year trial (2018–2020), while the model was also applied to cv LG Ayrton (high yield potential) and Izalco (high protein content) in the 2020–21 season. Yield and protein content trends in function of N rate were parabolic or sigmoidal respectively and both tillering and stem elongation rate contributed to increase the grain yield and protein content. Furthermore, the significant interaction between tillering and stem elongation fertilization on grain yield suggested the possibility of correcting the N deficiency after tillering fertilization with a further application. A calibration function for a variable rate application was established related to the CNSIs; all of them were good predictors but NDRE showed a higher overall correlation (R² = 0.479) with grain yield than NDVI (R²= 0.461) or the LCC values (R²= 0.236) considering all the 3 years of experiments. The model’s intercept was reduced according to the decrease in the grain yield goal. The model's validation was accomplished by comparing the outcomes predicted by the model yields with the measured. The yield’s Root Mean Square Error (RMSE) values were low for cv. Aubusson (0.85, on average) in all 3 years, while the RMSE was higher in 2021 for LG Ayrton (1.90) and Izalco (1.35), in a production situation with a higher yield potential. The results suggest that the topdressing N fertilization rate could be accurately determined from measured CNSI values for a site-specific N fertilization management, but they also highlight the requirement of a model adaptation for different genotypes and environments.

Context or problem

Partially substituting synthetic fertilizer by animal manure has been proposed as a sustainable agricultural practice, from the perspectives of improving soil quality and mitigating climate warming.

Objective or research question

Previous studies showed that manure application combined with synthetic fertilizer (MACSF) also altered soil nitrous oxide (N₂O) emissions, while the magnitude varied substantially among experiments. We hypothesized that the difference in local conditions may be responsible for the contrasting impact of MACSF on N₂O emissions, while their significance and relative importance have not been explicitly assessed.

Methods

In order to quantify the response of N₂O emissions to MACSF and its geographic variability, we conducted a meta-analysis by combining 291 observations from 103 sites across the globe. Also, we evaluated the impact of local conditions on N₂O emissions and compared their relative importance using the gradient boosting decision tree (GBDT) algorithm.

Results

Overall, MACSF did not have significant effect on soil N₂O emissions, with a global average effect size (ES) of 1.07 ± 0.10 (95 % confidence interval, CI) relative to the same amount of synthetic nitrogen fertilizer. The corresponding N₂O emission factor (EF) was estimated as 0.93 ± 0.13 % (95 % CI). However, both ES and EF varied substantially with local conditions, of which the substitution ratio (SR) and soil pH were identified as the most important factors. The ES increased significantly (p < 0.01) with the increasing SR. Critical SR was approx. 50 %, above which MACSF may exacerbate N₂O emissions. Moreover, both response indices increased significantly with the decreasing soil pH. MACSF in acidic soils (pH < 6.5) tended to increase N₂O emissions, with ES significantly (p < 0.05) higher than 1.0.

Conclusion

The contribution of MACSF to N₂O mitigation varies subustantially with local conditions, of which SR and soil pH are the most important two. MACSF reduces N₂O emissions only in the cases with low SR and neutral to alkaline soils.

Implications or significance

This study offers an integrative global synthesis of the impact of MACSF on N₂O emissions. By identifying the key controlling factors, the findings serve to guide the development of region-specific tailored substitution strategies, considering its contribution to N₂O emission mitigation.

Context

Double rice cropping system are crucial for sustainable food and security and agricultural ecosystem balance in South China. However, intensive chemical fertilization has reduced rice productivity, and soil and ecosystem degradation.

Objective

To develop a suitable organic fertilization scheme for double-rice cropping systems and explain its association with soil quality index (SQI), microbial diversity and ecological multifunctionality (EMF).

Methods

A 4-years field trial was conducted to examine the effects of four different organic materials (bio-organic fertilizer, OF; decomposed straw and manure, ST; biochar, BC and soil conditioner as silicon calcium magnesium fertilizer, SC) combined with chemical fertilizers (NPK) on rice yield, soil microbial abundance and diversity, SQI and EMF.

Results

Compared with NPK, NPK.OF and NPK.ST in early rice, and NPK.OF and NPK.BC in late rice both resulted in higher rice yield and SQI by enhancing soil microbes, soil dissolved organic carbon (DOC), and carbon (C)- and nitrogen (N)-cycle enzyme activities. Additionally, optimum organic fertilization increased soil bacterial abundance in early rice and that of fungi in late rice. Proteobacteria, Acidobacteriota, Bacteroidota and Nitrospirota were the dominant microbial groups in both rice seasons. Specifically, NPK.OF and NPK.ST increased the abundance of Bacteroidetes and Proteobacteria, but suppressed that of Acidobacteria and Nitrosospira in early rice. Conversely, the fungal community showed no significant changes with organic fertilization in late rice. Microbial phylogenetic diversity (PD) of bacteria and fungi showed positive linear relationships with soil EMF in both rice seasons. Heatmap analysis indicated that Proteobacteria and Nitrospirae can serve as bioindicators of soil EMF in response to organic fertilization in early rice. This was related to the soil indices of bacterial PD, and DOC. Random forest and structural equation model analyses revealed that soil bacterial PD, DOC, and N-functional enzymes were the primary drivers and predictors of EMF.

Conclusions

Soil bacterial diversity and its interactions with soil properties played an important role in determining rice productivity and EMF. Suitable fertilization management in the region include NPK.OF and NPK.ST for early rice, and NPK.OF and NPK.BC for late rice.

Implications

Optimum organic fertilization can achieve higher rice yield, SQI, and EMF in a double rice cropping system. However, future widespread application requires careful overall consideration of environmental factors, soil fertility and rice species in different ecological regions.

Context

Intercropping plays a crucial role in promoting agricultural sustainability and offers an alternative way to enhance crop production and ensure food security. However, the yield benefits and stability of oat/soybean intercropping have rarely been assessed across multiple sites and years, especially in semi-arid regions with low and unevenly distributed precipitation.

Objective

This study aimed to investigate the yield performance, yield stability, and economic benefits of oat/soybean strip intercropping through multiple sites and years of field experiments.

Methods

A three-year field experiment (2019–2021) with a completely randomized block design was conducted at three representative sites in semi-arid regions of China (i.e. Wulanchabu, Youyu, and Zhangjiakou). Each experiment included oat/soybean intercropping and corresponding monoculture with four replicates. Land equivalent ratio, yield stability, and economic income were compared between intercropping and monoculture.

Results

Over the three years, intercropping led to a substantial increase in oat yield, ranging from 21.7 % to 47.6 %, albeit accompanied by a reduction in soybean yield by 14.6–26.5 %, compared to corresponding monoculture. The results revealed a notable improvement in land use efficiency across all three sites with a mean land equivalent ratio (LER) of 1.12. Further analysis demonstrated that the yield enhancement of intercropped oat was evident not only in the border rows (2.21 times of monoculture) but also in the inner rows (1.13 times of monoculture), highlighting their combined contributions. Moreover, intercropping produced 5.2∼9.4 % higher net income on average across multiple sites and years. Additionally, intercropping exhibited 5.5∼62.6 % greater temporal yield stability compared to monoculture at two of three sites, and the temporal yield stability was positively correlated with crop yield and net income.

Conclusions

Oat/soybean strip intercropping emerges as a promising agronomic strategy to boost crop production while preserving relatively higher yield stability, thereby enhancing farmers' economic income across diverse semi-arid regions in China.

Implications

Our findings demonstrated the feasibility of the oat/soybean strip intercropping in semi-arid regions and evaluated its over-yield mechanisms, which is significant to agricultural sustainable development.

Context or problem

Cover crop mixtures that include complementary species can increase resource use efficiency, total cover crop biomass, and agroecosystem benefits. In the northeastern US, farmers need information on how climatic, environmental and management factors influence the performance of various cover crop mixtures. The development of site-specific seeding rates may be necessary to optimize cover crop mixture services and increase farmer adoption.

Objective or research question

The aim of this study was to characterize how site conditions influence mixture performance across the northeastern US, with total shoot biomass, species evenness (yield distribution of constituent species), and seed cost used as metrics of performance.

Methods

A field experiment was implemented at seven research farms across a latitudinal gradient in the northeast US, spanning from Maryland to Maine. Monocultures and 12 bicultures were established at 0 %, 25 %, 50 %, 100 %, and 150 % of the recommended rate of that species in monoculture. Winter cover crops from three plant families were planted: cereal rye (grass; Secale cereale L.), hairy vetch (legume; Vicia villosa Roth), and forage rape (brassica; Brassica napus L.), which were selected for their differing functional traits and popularity among northeastern growers.

Results

Classification and regression tree analysis showed that climate variables (spring growing degree days, hardiness zone) and soil conditions (soil nitrogen, pH, organic matter) were more influential on cover crop mixture performance than seeding rates of the constituent species. As soil inorganic nitrogen stocks increased, hairy vetch competitiveness and overall shoot biomass decreased compared to cereal rye or forage rape. Cereal rye dominated at sites with colder winters due to its winter hardiness compared to the other species. Forage rape shoot biomass was highly dependent on climate and performed poorly at colder sites.

Conclusions

In order to maximize mixture performance, it is important to understand initial soil nitrogen levels if including legumes. Sites with milder winters had more flexibility in species selection and could use lower seeding rates compared to colder sites to produce high yielding, multi-functional mixtures at lower overall seed costs. In colder climates, it is important to include cereal rye to ensure productive mixtures that establish early and are winter hardy.

Implications or significance

Understanding anticipated growing degree days in the cover crop season and baseline soil fertility is key when selecting species and seeding rates to ensure high performance of multi-functional mixtures.

Context

Forage species are widely planted in arid and semi-arid agro-pastoral regions to increase livestock carrying capacity and thereby relieve excessive grazing pressure. The effect of grazing on forage yield and relevant soil CO₂ emissions in sown pastures converted from cropland remains unclear.

Objective

The main objective of the study was to investigate the effect of utilization methods (grazing vs. haying) on annual and perennial forage yields and soil CO₂ emissions during the growing seasons in saline cropland soils and to derive the optimum number of continuous utilization years based on the combined consideration of forage productivity and soil CO₂ emission.

Methods

Stands of annual and perennial forage species were established in a saline cropland area of northwest China in a 4-year experiment to investigate the effect of sheep grazing and haying on soil CO₂ emissions during the growing seasons. The relationships between soil CO₂ fluxes and soil properties were fitted. In addition, yield-scaled soil CO₂ emissions were used as an index to evaluate forage productivity.

Results

Grazing significantly increased the mean forage yield by 44 % and 14 % over that of haying, and significantly decreased the mean yield-scaled soil CO₂ emissions (CO₂ emission intensity, CO₂EI, kg of CO₂ kg⁻¹ of dry forage yield) by 36 % and 23 % over that of haying in the annual and perennial stands, respectively, from 2014 to 2017. Grazing did not differ from haying for cumulative soil CO₂ flux during the growing seasons in the annual forages but had 17 % lesser (P < 0.05) cumulative CO₂ flux in the perennial forages in 2015. A negative correlation (r = –0.55, P < 0.05) between soil CO₂ flux and soil water content was found in the perennial forages but not in the annual forages. Multiple linear regression results indicated that soil temperature accounted for ≥ 72 % of the variation in soil CO₂ flux. Results of the structural equation model indicated, whether annual or perennial sown pastures, that grazing had the greatest positive effect on forage yield and the greatest negative effect on soil CO₂EI.

Conclusion

Grazing mainly reduced the soil CO₂EI by increasing forage yield in annual sown pastures and by reducing soil respiration in perennial pastures. Grazing is the optimal approach to improving forage production while mitigating soil CO₂ emissions in sown pasture in continental arid regions.

Context: I

ncreasing rice yield potential is an important strategy for meeting rising food demand and achieving global food security. MP3 was recently identified as a quantitative trait locus (QTL) in rice that increases panicle number and thereby sink size (the total number of spikelets per square meter). Under current climatic conditions, MP3 did not increase grain yield in a high-yielding cultivar in the absence of improved source traits.

Objective:

This study aimed to determine whether MP3 increases grain yield in a rice cultivar background with improved biomass production and to analyze the key variables linked to yield improvement.

Methods

Two-year experiments were carried out on a paddy field with nitrogen (N) applications in Tsukuba, Japan. Near-isogenic MP3 lines, Hokuriku 193-MP3 and IR64-MP3, were used in conjunction with their parental cultivars. Hokuriku 193 is a high-yielding cultivar in Japan with high biomass production, and IR64 is a high-yielding mega-cultivar in the tropics.

Results

Both Hokuriku 193-MP3 and IR64-MP3 increased panicle quantity and sink size when compared to the parental cultivars, regardless of N treatment. Hokuriku 193-MP3 had a 7 % higher grain yield than Hokuriku 193; however, IR64-MP3 did not yield more than IR64. Hokuriku 193 and Hokuriku 193-MP3 had larger leaf areas, higher biomass, and accumulated more non-structural carbohydrate (NSC) in the culms and leaf sheaths at heading than IR64 and IR64-MP3. Hokuriku 193-MP3 significantly reduced the NSC level in the culm and leaf sheaths at 16 d after heading and had a higher harvest index than Hokuriku 193; however, IR64-MP3 did not differ from IR64 with regard to these variables.

Conclusion

Hokuriku 193 has surplus source and translocation abilities that can fill the MP3-enlarged sink, resulting in a higher grain yield. In comparison, IR64 lacks these abilities. These findings imply that MP3 has boosted the yield potential of rice cultivars in Japan, with Hokuriku 193 having the highest yield in Japan.

Significance

This study shows that balanced improvements in sink, source, and translocation are essential for increasing rice yield potential. MP3 and the high source and translocation traits of Hokuriku 193 could benefit future high yield breeding initiatives around the world.

Context and problem

The overall greenhouse effects of rice paddy fields are influenced by the balance between greenhouse gas (GHG) emissions and soil organic carbon sequestration (SOCS). Studies on how straw return impacts GHG emissions and SOCS under different water regimes—specifically, conventional irrigation (CI) and alternate wetting and moderate drying (AWMD)—are crucial for developing strategies to mitigate the greenhouse effect in rice paddy fields.

Objective

This study aimed to develop a strategy for decreasing GHG emissions, improving SOCS, and increasing grain yield of rice paddy fields under long-term straw return.

Methods

Different water regimes were introduced after six years of straw return in the rice paddy field, and there were four treatments: straw removal and CI (N-CI), straw removal and AWMD (N-AWMD), straw return and CI (R-CI), and straw return and AWMD (R-AWMD). We studied various traits related to soil organic carbon sequestration capacity and GHG emissions over three years to investigate the effects of combination of AWMD and straw return on the GHG emission from paddy field.

Results

Straw return significantly increased net greenhouse gas emissions (NGHGE) and seasonal soil total organic carbon sequestration rate (TOCSR) due to substantial quantity of straw inputs. On average, straw return increased NGHGE by 2.125 t CO₂ ha^–1 and TOCSR by 393.2 kg C ha^–1, respectively. AWMD could mitigate the greenhouse effects caused by straw return by decreasing NGHGE by 28.0 %, primarily attributed to the reduction in CH₄ emissions (-27.0 %), which outweighed the effects of increased N₂O and CO₂ emissions. Although AWMD did not increase the overall soil organic carbon (SOC) content, it optimized the composition of SOC by increasing the percentage of microbial-derived C, including fungal necromass C (FNC) and bacterial necromass C (BNC), which are more stable than plant-derived C. The aerobic environment in AWMD combined with straw return enhanced the activities of microbes, which promoted the conversion of plant residue C to FNC and BNC and improved soil carbon sequestration.

Conclusions

The combination of straw return with AWMD can reduce GHG emission, and optimize soil carbon sequestration by stimulating microbial necromass carbon accumulation.

Implication

This study offers valuable insights into mitigating GHG emissions and enhancing soil organic carbon sequestration in high-yielding rice system through the combined adoption of AWMD and straw return.

Context and problem

Wheat following rice manly distributed in the lower reaches of Yangtze River of China, its major challenge is to cope with simultaneous improvement in yield and nitrogen use efficiency (NUE) without increasing the input of fertilizer.

Objective

Controlled-release urea (CRU) offer several advantages in agricultural practices. However, the effectiveness of CRU was strongly affected by the application strategy, types and region environmental conditions. This study investigated if and how the controlled-release nitrogen strategy could achieve high yield and high NUE.

Methods

Field experiments across two years using two spring wheat varieties were conducted with five nitrogen application treatments, including no nitrogen (T1), conventional urea (T2, CK), controlled-release urea (T3), CRU combined with one-time basal CU (T4) and CRU combined with split CU (T5).

Results

The results showed that yield and NUE were significantly increased in optimized controlled-release nitrogen strategy (T4 and T5) compared to T2, especially for T4. T4 significantly improved biomass accumulation after anthesis, non-structural carbohydrates remobilization and harvest index (HI), increased nitrogen absorption and nitrogen harvest index (NHI), enhanced leaf photosynthetic capacity (leaf area index, photosynthetic rate, chlorophyll content) and leaf nitrogen metabolism enzyme activities. The diversity of nitrogen-fixing microorganisms and relative abundance of Bradyrhizobium in rhizosphere after anthesis were significantly increased in T4. Correlation analysis showed that the above morpho-physiological indexes were positively and significantly correlated with grain yield and NUE.

Conclusions

This study indicates that the appropriate combined application strategy (CRU combined with one-time basal CU) could hold great promise to increase yield and NUE of wheat via facilitating carbon-nitrogen allocation and optimizing rhizosphere environment in the lower reaches of Yangtze River of China.

Implication

This study would offer theoretical basis for achieving high yield and nitrogen use efficiency through combined application strategy of controlled-release and convention urea, and provide practical guidance in high efficiency production in wheat-rice rotation system.