Combined Application of Leguminous Green Manure and Straw Determined Grain Yield and Nutrient Use Efficiency in Wheat-Maize-Sunflower Rotations System in Northwest China.

Leguminous green manure (LGM) has a reputation for improving crop productivity. However, little is known about the beneficial interactions with straw on crop yield and nutrient (N, P, K) use efficiency. Herein, a 9-year field experiment (from 2015 to 2023) containing three treatments-(1) chemical fertilizer as the control (CK), (2) NPK + straw return (Straw) and (3) NPK + straw return with LGM (Straw + LGM)-was conducted to investigate whether the combined application of LGM and straw can increase productivity and nutrient use efficiency in the wheat-maize-sunflower diversified cropping rotation. The results showed that in the third rotation (2021-2023), Straw + LGM significantly increased wheat yield by 10.2% and maize yield by 19.9% compared to CK. The total equivalent yield under Straw + LGM was the highest (26.09 Mg ha-1), exceeding Straw and CK treatments by 2.7% and 12.3%, respectively. For each 2 Mg ha-1 increase in straw returned to the field, sunflower yield increased by 0.2 Mg ha-1, whereas for each 1 Mg ha-1 increase in LGM yield from the previous crop, sunflower yield increased by 0.45 Mg ha-1. Compared to CK, the co-application of LGM and straw increased the N use efficiency of maize in the first and third rotation cycle by 70.6% and 55.8%, respectively, and the P use efficiency by 147.8% in the third rotation cycle. Moreover, Straw treatment led to an increase of net income from wheat and sunflower by 14.5% and 44.6%, while Straw + LGM increased the net income from maize by 15.8% in the third rotation cycle. Combining leguminous green manure with a diversified cropping rotation has greater potential to improve nutrient use efficiency, crop productivity and net income, which can be recommended as a sustainable agronomic practice in the Hetao District, Northwest China.

Fertilization and cultivation management promotes soil phosphorus availability by enhancing soil P-cycling enzymes and the phosphatase encoding genes in bulk and rhizosphere soil of a maize crop in sloping cropland.

Fertilization and cultivation managements exert significant effects on crop growth and soil-associated nutrients in croplands. However, there is a lack of knowledge regarding how these practices affect soil phosphorus-cycling enzymes and functional genes involved in regulating global P-cycling, especially under intense agricultural management practices in sloping croplands. A long-term field (15-year) trial was conducted in a 15° sloping field based on five treatments: no fertilizer amendments + downslope cultivation (CK); mixed treatment of mineral fertilizer and organic manure + downslope cultivation (T1); mineral fertilizer alone + downslope cultivation (T2); 1.5-fold mineral fertilizer + downslope cultivation (T3); and mineral fertilizer + contour cultivation (T4). Bulk and rhizosphere soil samples were collected after the maize crop was harvested to determine the P fraction, P-cycling enzymes, and phosphatase-encoding genes. Results indicated that fertilization management significantly increased the inorganic (Pi) and organic soil (Po) P fractions compared to CK, except for NaOH-extractable Po in T1 and T3 in bulk and rhizosphere soils, respectively. For the cultivation treatments, the content of Pi pools in the downslope cultivation of T1 and T3 was significantly larger than that in the contour cultivation of T4 in bulk and rhizosphere soils. However, the content of NaOH-extractable Po in T1 and T3 was lower compared to T4 in bulk soil and vice versa for the NaHCO3-P and HCl-Po fractions in the rhizosphere. We also found that fertilization and cultivation managements significantly increased the activity of acid phosphatase (ACP), alkaline phosphatase (ALP), phytase, phosphodiesterases (PDE), and phoC and phoD gene abundance in bulk and rhizosphere soils, with a larger effect on the activity of ALP and the phosphatase encoding phoD gene, especially in T1 and T3 in the rhizosphere. Soil organic carbon (SOC) and microbial biomass C and P (MBC and MBP) were the main predictors for regulating P-cycling enzymes and phoC- and phoD gene abundance. A strong association of P-cycling enzymes, especially ALP and phytase, and the abundance of phoD genes with the P fraction indicated that the soil P cycle was mainly mediated by microbial-related processes. Together, our results demonstrated that an adequate amount of mineral fertilizer alone or combined with organic fertilizer plus downslope cultivation is more effective in promoting soil P availability by enhancing the activity of ALP, phytase, and phoD genes. This provides valuable information for sustaining soil microbial-regulated P management practices in similar agricultural lands worldwide.

Long-term chemical fertilization results in a loss of temporal dynamics of diazotrophic communities in the wheat rhizosphere.

Diazotrophs are potential bacterial biofertilizers with efficacy for plant nutrition, which convert atmospheric N2 into plant available nitrogen. Although they are known to respond strongly to fertilization, little is known about the temporal dynamics of diazotrophic communities throughout plant developmental under different fertilization regimes. In this study, we investigated diazotrophic communities in the wheat rhizosphere at four developmental stages under three long-term fertilization regimes: no fertilizer (Control), chemical NPK fertilizer only (NPK), and NPK fertilizer plus cow manure (NPKM). Fertilization regime had greater effect (explained of 54.9 %) on diazotrophic community structure than developmental stage (explained of 4.8 %). NPK fertilization decreased the diazotrophic diversity and abundance to one-third of the Control, although this was largely recovered by the addition of manure. Meanwhile, Control treatment resulted in significant variation in diazotrophic abundance, diversity, and community structure (P = 0.001) depending on the developmental stage, while the NPK fertilization resulted in the loss of temporal dynamics of the diazotrophic community (P = 0.330), which could be largely recovered by the addition of manure (P = 0.011). Keystone species identified in this study were quite different among the four developmental stages under Control and NPKM treatment but were similar among stages under NPK treatment. These findings suggest that long-term chemical fertilization not only reduces diazotrophic diversity and abundance, but also results in a loss of temporal dynamics of rhizosphere diazotrophic communities.

[Differences in uptake, utilization and loss of nitrogen and phosphorus in a Chinese double rice cropping system under different irrigation and fertilization managements]. / 不同水肥耦合下双季稻氮磷吸收、利用与流失差异.

In order to optimize water and fertilizer use in the double-cropping rice in eastern Fujian Province, a field runoff plot experiment was conducted to investigate rice yield, nutrient uptake, and runoff losses of N (nitrogen) and P (phosphorus) in the T0(no chemical fertilization with traditional flooding irrigation), T1(common chemical fertilizer of 273 kg N·hm-2, 59 kg P·hm-2, and 112 kg K·hm-2 combined with traditional flooding irrigation), T2(chemical fertilizer of 240 kg N·hm-2, 52 kg P·hm-2, and 198 kg K·hm-2 combined with traditional flooding irrigation) and T3(chemical fertilizer combined with shallow intermittent irrigation) treatments. Results showed that early rice grain yield in the T1, T2 and T3 treatments significantly increased by 0.7, 1.0, 1.1 times, late rice grain yield significantly increased by 0.9, 1.1, 1.0 times compared to that in the T0 treatment, respectively. The T1, T2 and T3 treatments significantly increased the uptake of N and P in aboveground parts of the plants, especially in grains. The T1, T2 and T3 treatments significantly increased N uptake by 1.1, 1.2, 1.2 times, increased P uptake by 0.9, 1.4, 1.6 times in early-season grains, and significantly increased N uptake by 0.8, 1.0, 1.0 times, increased P uptake by 0.7, 0.9, 0.9 times in late-season grains, compared to T0, respectively. Furthermore, T3 increased agronomic N use efficiency (AEN) and agronomic P use efficiency (AEP) by 71.1% and 69.2% in early rice plants, increased AEN and AEP by 26.4% and 25.0% in late rice plants, whereas T3 decreased total dissolved N (DN) by 16.0% in comparison with T1. Dissolved inorganic N loss in surface runoff occurred mainly in the form of NO3--N (nitrate N) under different water and fertilizer regimes. However, there were no significant differences in AEN and AEP between T2 and T3 treatments. These findings suggested that optimal applications of water and fertilizers (T3) might increase N and P uptake in rice plants, maintain yield, and reduce N loss, especially in the form of NO3--N in surface water from early rice field. In general, this study could provide theoretical support for the optimization of irrigation and fertilization and for the control of N and P non-point source pollution from the double cropping rice paddy fields in eastern Fujian Province.

The Proportion of Soil-Borne Fungal Pathogens Increases with Elevated Organic Carbon in Agricultural Soils.

Soil-borne fungal phytopathogens are important threats to soil and crop health. However, their community composition and environmental determinants remain unclear. Here, we explored the effects of agricultural fertilization regime (i.e., organic material application) on soil fungal phytopathogens, using data sets from a combination of field survey and long-term experiment. We found that soil organic carbon was the key factor that affected the diversity and relative abundance of fungal phytopathogens in agricultural soils. The dominant genera of phytopathogens including Monographella was also strongly associated with soil organic carbon. In addition, the elevated soil organic carbon enhanced the node proportion of phytopathogens and the positive interactions within the fungal community in the network. Results of the long-term experiment revealed that applications of crop straw and fresh livestock manure significantly increased the proportion of phytopathogens, which were associated with the elevated soil organic carbon. This work offers new insights into the occurrence and environmental factors of fungal phytopathogens in agricultural soils, which are fundamental to control their impacts on the soil and crop systems. IMPORTANCE Fungal phytopathogens are important threats to soil and crop health, but their community composition and environmental determinants remain unclear. We found that soil organic carbon is the key factor of the prevalence of fungal phytopathogens through a field survey, which is also supported by our long-term (6-year) experiment showing the applications of crop straw and fresh livestock manure significantly increased the proportion of fungal phytopathogens. These findings advance our understanding of the occurrence and environmental drivers of soil-borne fungal phytopathogens under agricultural fertilization regime and have important implications for the control of soil-borne pathogens.

Fruits-Based Critical Nitrogen Dilution Curve for Diagnosing Nitrogen Status in Cotton.

Estimating the precise nutritional status of crop nitrogen (N) after flowering period is not only important to predict deficiency but the excess that could be revised by fertilization in future crops. Critical N dilution curves describing the critical N concentration ([N]c) in plant tissues during crop growth have been used to estimate the N status of whole plants in cotton. Little is known, however, about the critical N dilution curve for specific plant organs such as cotton fruits. The objective of this study was to verify the feasibility of fruits-based critical N dilution curve as a useful diagnostic tool for diagnosing the N status of cotton crops. A 3-year field experiment was conducted with seven N application rates (0-360 kg N ha-1) using the high-yielding cultivars Jimian 228 and Lumian 28, which differ in maturity. The relationship between fruits dry mass (DM) and N concentration ([N]) was analyzed, and a model of [N]c for cotton fruits was constructed and validated. The results showed that fruits [N]c decreased with increasing fruits DM. The critical N dilution curve based on cotton fruits was described by the equation [N]c = 2.49 × DM-0.12 (R 2 = 0.649, P < 0.0001) across cultivar-years. The N nutrition index (NNI) of the fruits (NNIf) with the N dilution curve was significantly related to the NNI of shoot DM, relative yield (RY), and boll density at most sampling dates. For an NNIf of approximately 1, the RY was nearly 95%, while it decreased with a decreasing NNIf below 1. The petiole nitrate-N (NO3-N) concentration was also linearly related to the NNIf, suggesting that the NO3-N concentration in the petiole was a good predictor of the NNIf. Therefore, fruits-based critical N dilution curve and the derived NNIf values will serve as a useful diagnostic tool for diagnosing N status in cotton crops.

[Effects of Water and Fertilization Management on CH4 and N2O Emissions in Double-rice Paddy Fields in Tropical Regions].

Paddy soils are widely considered a main source of methane (CH4) and nitrous oxide (N2O). Comprehensively evaluating CH4 and N2O emissions from double-rice systems in tropical regions with different water irrigation and fertilizer applications is of great significance for addressing greenhouse gas emissions from such systems in China. In this study, eight treatments were evaluated:conventional irrigation-PK fertilizer (D-PK), conventional irrigation-NPK fertilizer (D-NPK), conventional irrigation-NPK+organic fertilizer (D-NPK+M), conventional irrigation-organic fertilizer (D-M), continuous flooding-PK fertilizer (F-PK), continuous flooding-NPK fertilizer (F-NPK), continuous flooding-NPK+organic fertilizer (F-NPK+M), and continuous flooding-organic fertilizer (F-M). CH4 and N2O emissions in double-rice fields in tropical region of china were monitored in situ by closed static chamber-chromatography method and crop yields as well as global warming potential (GWP) and greenhouse gas intensity (GHGI) were determined. The results show that:① The cumulative CH4 emissions from early rice and late rice are 10.3-78.9 kg·hm-2and 84.6-185.5 kg·hm-2, respectively. Compared with F-PK and F-NPK treatments, F-NPK+M and F-M treatments significantly increased the cumulative emissions of CH4 from early rice season. Under the same fertilizer conditions, the cumulative CH4 emissions under continuous flooding condition were significantly higher than that under conventional irrigation condition. Irrigation and fertilization had extremely significant effects on CH4 emission in the early rice season. ② The cumulative N2O emissions across all treatments were 0.18-0.76 kg·hm-2 in early rice season and 0.15-0.58 kg·hm-2in late rice season, respectively. During early rice season, compared with F-PK, F-NPK significantly increased the cumulative N2O emission; however, compared with D-PK, D-NPK, D-NPK+M, and D-M treatments significantly increased the cumulative N2O emissions. Compared with F-PK, other three treatments under continuous flooding condition significantly increased N2O cumulative emission in late rice season; compared with D-PK, D-NPK, and D-M treatment significantly increased the cumulative N2O emission. Irrigation and fertilization had significant impacts on N2O emissions in late rice season, and fertilization had significant impacts on N2O emission in early rice season. ③ Early and late rice yields were 7310.7-9402.4 kg·hm-2 and 3902.8-7354.6 kg·hm-2, respectively. Early rice yields in both F-NPK and F-M treatments were significantly higher than those in F-PK, D-PK, and D-NPK treatments. Compared with PK, the other three fertilization treatments under the same irrigation condition significantly increased late rice yield. The GWP and GHGI in early rice season were 580.8-2818.5 kg·hm-2and 0.08-0.30 kg·kg-1, respectively. There was no significant difference in GWP among four fertilizer treatments under conventional irrigation condition in the early rice season. However, F-NPK+M and F-M treatments had a significant increase in GWP compared with F-PK. The GHGI in F-NPK+M and F-M treatments were significantly higher than that in other treatments. The GWP and GHGI in late rice season were 3091.6-6334.2 kg·hm-2 and 0.50-1.23 kg·kg-1, respectively. Irrigation significantly affected GWP and GHGI in both early and late rice seasons but fertilization had no significant impact on GWP and GHGI in late rice season. ④ Correlation analysis results showed that soil NH4+-N content and soil temperature below 5 cm soil layer had an extremely significant negative correlation with CH4 emissions. Soil pH was extremely significant positive correlated with CH4 emissions but significantly negatively correlated with N2O emission. Soil NH4+-N and NO3--N concentrations were extremely significantly negatively correlated with N2O emission. Given crop yield, GWP, GHGI, and D-NPK+M can be recommended for local water and fertilizer management to reduce greenhouse gas emissions while maintaining rice yields.

Determination of Nutrients in Liquid Manures and Biogas Digestates by Portable Energy-Dispersive X-ray Fluorescence Spectrometry.

Knowing the exact nutrient composition of organic fertilizers is a prerequisite for their appropriate application to improve yield and to avoid environmental pollution by over-fertilization. Traditional standard chemical analysis is cost and time-consuming and thus it is unsuitable for a rapid analysis before manure application. As a possible alternative, a handheld X-ray fluorescence (XRF) spectrometer was tested to enable a fast, simultaneous, and on-site analysis of several elements. A set of 62 liquid pig and cattle manures as well as biogas digestates were collected, intensively homogenized and analysed for the macro plant nutrients phosphorus, potassium, magnesium, calcium, and sulphur as well as the micro nutrients manganese, iron, copper, and zinc using the standard lab procedure. The effect of four different sample preparation steps (original, dried, filtered, and dried filter residues) on XRF measurement accuracy was examined. Therefore, XRF results were correlated with values of the reference analysis. The best R2s for each element ranged from 0.64 to 0.92. Comparing the four preparation steps, XRF results for dried samples showed good correlations (0.64 and 0.86) for all elements. XRF measurements using dried filter residues showed also good correlations with R2s between 0.65 and 0.91 except for P, Mg, and Ca. In contrast, correlation analysis for liquid samples (original and filtered) resulted in lower R2s from 0.02 to 0.68, except for K (0.83 and 0.87, respectively). Based on these results, it can be concluded that handheld XRF is a promising measuring system for element analysis in manures and digestates.

Effects of fermented organic fertilizer application on soil N2O emission under the vegetable rotation in polyhouse.

Vegetable field is one of the main sources of soil nitrous oxide (N2O) emission, yet soil N2O emission from vegetable rotation with combined application of fermented organic fertilizer with inorganic fertilizer in polyhouse is not well evaluated. In this study, we investigated the soil N2O emission in cabbage-tomato rotation management system under different treatments of fertilizer nitrogen (N) sources, including: 100% inorganic fertilizer (IF), 75% IF+25% fermented organic fertilizer (OF), 50% IF+50% OF, 75% IF+25% OF, 100% OF, and no fertilizer (CK). The fertilization amount of N was 180 kg ha-1 to cabbage and 200 kg ha-1 to tomato. Results showed that soil N2O emission flux was in a high level during 1-3 days after basal fertilization for cabbage, and decreased as the proportions of OF increased. During the whole cabbage-tomato rotated cultivation, N2O emission flux was positively related to soil NO3--N and NH4+-N contents, with correlation coefficients of 0.72 and 0.90, respectively. A higher proportion of OF increased the soil total carbon (C), organic C and C/N ratio, but decreased the soil nitrifiers and denitrifiers. The fertilizer N loss caused by N2O emission under different OF treatments was 1.23-2.77%, significantly (p < 0.05) lower than under 100% IF treatment (3.58%), and the loss decreased with the increase of OF proportion. Our study quantitatively revealed the N2O emission under vegetable rotation systems with different fertilizations in polyhouses, and the overall results suggested that the higher soil pH, the lower soil mineral NO3--N and NH4+-N as well as lower soil nitrifiers and denitrifiers contributed to less N2O emission for the OF treatments.

Impact of Long-Term Organic and Mineral Fertilization on Rhizosphere Metabolites, Root-Microbial Interactions and Plant Health of Lettuce.

Fertilization management can affect plant performance and soil microbiota, involving still poorly understood rhizosphere interactions. We hypothesized that fertilization practice exerts specific effects on rhizodeposition with consequences for recruitment of rhizosphere microbiota and plant performance. To address this hypothesis, we conducted a minirhizotron experiment using lettuce as model plant and field soils with contrasting properties from two long-term field experiments (HUB-LTE: loamy sand, DOK-LTE: silty loam) with organic and mineral fertilization history. Increased relative abundance of plant-beneficial arbuscular mycorrhizal fungi and fungal pathotrophs were characteristic of the rhizospheres in the organically managed soils (HU-org; BIODYN2). Accordingly, defense-related genes were systemically expressed in shoot tissues of the respective plants. As a site-specific effect, high relative occurrence of the fungal lettuce pathogen Olpidium sp. (76-90%) was recorded in the rhizosphere, both under long-term organic and mineral fertilization at the DOK-LTE site, likely supporting Olpidium infection due to a lower water drainage potential compared to the sandy HUB-LTE soils. However, plant growth depressions and Olpidium infection were exclusively recorded in the BIODYN2 soil with organic fertilization history. This was associated with a drastic (87-97%) reduction in rhizosphere abundance of potentially plant-beneficial microbiota (Pseudomonadaceae, Mortierella elongata) and reduced concentrations of the antifungal root exudate benzoate, known to be increased in presence of Pseudomonas spp. In contrast, high relative abundance of Pseudomonadaceae (Gammaproteobacteria) in the rhizosphere of plants grown in soils with long-term mineral fertilization (61-74%) coincided with high rhizosphere concentrations of chemotactic dicarboxylates (succinate, malate) and a high C (sugar)/N (amino acid) ratio, known to support the growth of Gammaproteobacteria. This was related with generally lower systemic expression of plant defense genes as compared with organic fertilization history. Our results suggest a complex network of belowground interactions among root exudates, site-specific factors and rhizosphere microbiota, modulating the impact of fertilization management with consequences for plant health and performance.

Formation of soursop seedlings irrigated using waters with different salinity levels and nitrogen fertilization / Formação de mudas de gravioleira irrigadas com águas de distintas salinidades e adubação nitrogenada

Using saline waters in agriculture has become common in many regions worldwide, but some techniques have been developed to enable the use of these waters in order not to harm the crop. Thus, this study aimed to evaluate the growth of soursop seedlings, cv. 'Morada Nova', under interaction between salt stress and nitrogen (N) fertilization. The experiment was conducted in a greenhouse in randomized block design, in 5 x 4 factorial scheme, with 4 replicates, formed by the combination of five levels of irrigation water electrical conductivity - ECw (0.3; 1.1; 1.9; 2.4 and 3.5 dS m-¹) and four N doses (70, 100, 130 and 160%). The dose relative to 100% corresponded to 100 mg of N dm-³ of soil. The interaction between N doses and water salinity levels did not affect the seedling production stage of soursop, cv. 'Morada Nova'. The growth of 'Morada Nova' soursop seedlings subjected to different water salinity levels was less affected in the initial stage (45 days after treatment application). Water with ECw of 2.0 dS m-¹ can be used to produce soursop seedlings, because it leads to an acceptable mean growth reduction of 10%. N doses higher than 70 mg dm-³ do not either attenuate salt stress or promote higher growth of soursop seedlings, cv. 'Morada Nova'.

O uso de águas salinas na agricultura tornou-se um fato corriqueiro em diversas regiões do mundo. Contudo algumas técnicas têm sido desenvolvidas para viabilizar o uso dessas águas de modo a não prejudicar a cultura. Neste sentido, objetivou-se avaliar o crescimento de mudas de gravioleira cv. Morada Nova sob interação entre a salinidade da água de irrigação e adubação nitrogenada. Desenvolvida em casa de vegetação em delineamento de blocos casualizados em esquema fatorial 5 x 4, com quatro repetições, constituído pela combinação de cinco condutividade elétrica da água de irrigação CEa (0.3; 1.1; 1.9; 2.4 e 3.5 dS m-¹) e quatro doses (70, 100, 130 e 160% de nitrogênio). Sendo a dose referente a 100%, correspondente a 100 mg de N por dm-³ de solo. A interação entre os fatores doses de nitrogênio e níveis de salinidade da água não afetaram a fase de produção de mudas de gravioleira cv. Morada Nova. O crescimento das mudas de gravioleira cv. Morada Nova, submetidas a diferentes níveis de salinidade da água foi menos comprometido pela salinidade na fase inicial (45 Dias após aplicação dos tratamentos). Na produção de mudas de gravioleira pode-se usar água de CEa de até 2.0 dS m-¹ pois proporciona redução média aceitável de 10% no crescimento. Doses de nitrogênio superior a 70 mg de N dm-³ de solo não atenuam o estresse salino nem promovem maior crescimento de mudas de gravioleira cv. Morada Nova.

Effects of long-term fertilization on arbuscular mycorrhizal fungal community in lime concretion black soil.

In agroecosystem, arbuscular mycorrhizal fungi have mutually beneficial symbiosis with roots of many crops. Meanwhile, this special fungal community is also affected by agricultural mana-gements such as fertilization. The objective of this study was to investigate the effects of long-term fertilization managements (no fertilizer, chemical fertilizer, chemical fertilizer combined with straw, chemical fertilizer combined with manure) on arbuscular mycorrhizal fungal community (AM fungal community) in lime concretion black soil, and to identify the indicator species in each fertilization regime. The most dominant arbuscular mycorrhizal fungal phyla in lime concretion black soil were Archaeosporaceae, Diversisporaceae, Gigasporaceae, Claroideoglomeraceae, Glomeraceae and Paraglomeraceae. The genus Paraglomus was strongly and significantly associated with the application of chemical fertilizer and organic fertilizer. Compared with the control, long-term application of chemical fertilizer greatly changed AM fungal community structure and resulted in the decrease of AM fungal diversity, and the addition of wheat straw further decreased the diversity, while the addition of manure could alleviate diversity loss resulted from chemical fertilization. Soil pH and dissolved organic carbon (DOC) were the main factors affecting the changes of AM fungal community. In summary, long-term application of chemical fertilizer combined with different organic materials had different impacts on soil AM fungal community structure and diversity. The combination of chemical fertilizer and manure would be more conducive to the maintenance of AM fungal diversity.