Excess Nitrogen Research Articles

Phosphorus depletion is exacerbated by increasing nitrogen loading in the Bohai sea

Phosphorus (P) is an essential nutrient for algal growth in nearshore ecosystems. In recent years, there has been a shift in nutrient dynamics in nearshore areas, leading to an exacerbation of P limitation, although the underlying mechanisms remain unclear. This study analyzed the P species and budget in the Bohai Sea (BS) from 2011 to 2020, aiming to explore the intrinsic mechanisms of P limitation in the BS. The results show that the main external source of P in the BS was river transport (89%), and the primary fate of P was burial (96%) into the sediment. Due to excessive nitrogen (N) input and biological processes in the BS, the P budget in the BS is unbalanced, resulting in an increase in the N/P ratio, particularly in nearshore areas. Nearshore areas typically have lower concentrations of dissolved inorganic P (DIP) in the water and higher concentrations of reactive P (Reac-P) in the sediments. This pattern is particularly evident in Bohai Bay and the northwest nearshore region, where harmful algal blooms occur frequently. To cope with enhanced P limitation, the biologically driven P regeneration and cycling processes within the BS are accelerated. From 2011 to 2020, the concentration of DIP in the BS during autumn increased, while the content of Reac-P in sediments slightly decreased. Historical data indicate that P depletion in the BS is intensifying and expanding, primarily due to N enrichment and algal production. N enrichment alters the structure and composition of primary production, potentially exacerbating P depletion in the BS. Excessive N may have significant impacts on the P pool, potentially influencing the stability of future coastal ecosystems.

Does invasive submerged macrophyte diversity affect dissimilatory nitrate reduction processes in sediments with varying microplastics?

Nitrogen removal is essential for restoring eutrophic lakes. Microorganisms and aquatic plants in lakes are both crucial for removing excess nitrogen. However, microplastic (MP) pollution and the invasion of exotic aquatic plants have become increasingly serious in lake ecosystems due to human activity and plant-dominant traits. This field mesocosm study explored how the diversity of invasive submerged macrophytes affects denitrification (DNF), anammox (ANA), and dissimilatory nitrate reduction to ammonium (DNRA) in lake sediments with varying MPs. Results showed that invasive macrophytes suppressed DNF rates, but DNRA and ANA were less sensitive than DNF to the diversity of invasive species. Sediment MPs increased the biomass of invasive species more than native species, but did not affect microbial processes. The effects of MPs on nitrate dissimilatory reduction were process-specific. MPs increased DNF rates and the competitive advantage of DNF over DNRA by changing the sediment environment. The decoupling of DNF and ANA was also observed, with increased DNF rates and decreased ANA rates. The study findings suggested new insights into how the invasion of exotic submerged macrophytes affects the sediment nitrogen cycle complex environments.

Long-term excessive nitrogen application decreases spring maize nitrogen use efficiency via suppressing root physiological characteristics

Long-term excessive nitrogen application decreases spring maize nitrogen use efficiency via suppressing root physiological characteristics

Effects of microorganisms on nitrogen and phosphorus removal from wastewater

Nitrogen and phosphorus are key to plant growth. The balance of nitrogen and phosphorus is crucial in nature. Excessive nitrogen and phosphorus content in wastewater has caused great harm to the environment. Traditional nitrogen and phosphorus removal methods can no longer meet the treatment standards for nitrogen and phosphorus. This article introduces the hazards of nitrogen and phosphorus, and points out the harm to nature and human beings if they are not up to standard in wastewater treatment plants. Through the analysis and discussion of several methods, the advantages of microbial nitrogen and phosphorus removal are explained. This article further summarizes several representative new microorganisms and microbial processes through the types and mechanisms of microbial nitrogen and phosphorus removal. Anammox bacteria can accept other electron pools to increase nitrogen removal efficiency. Denitrifying phosphorus-removing bacteria can achieve energy saving and carbon reducing effects through endogenous denitrification. Besides, the enhanced biological phosphorus removal process can allow denitrifying phosphorus accumulating bacteria to absorb phosphorus in an anaerobic, anoxic, aerobic alternating environment. The moving bed biofilm reactor (MBBR) abandons the disadvantages of the traditional biofilm method, while retaining the advantages of the traditional biofilm method such as shock load resistance and low sludge production. These new microorganisms and new microbial processes have become important applications in future nitrogen and phosphorus removal processes due to their advantages of high efficiency, low energy, and no secondary pollution. This article is conducive to the promotion of microbial-based wastewater treatment and can provide suggestions for the sustainable development of wastewater treatment.

Redistribution of nitrogen to feed the people on a safer planet.

Lack of nitrogen limits food production in poor countries while excessive nitrogen use in industrial countries has led to transgression of the planetary boundary. However, the potential of spatial redistribution of nitrogen input for food security when returning to the safe boundary has not been quantified in a robust manner. Using an emulator of a global gridded crop model ensemble, we found that redistribution of current nitrogen input to major cereals among countries can double production in the most food-insecure countries, while increasing global production of these crops by 12% with no notable regional loss or reducing the nitrogen input to the current production by one-third. Redistribution of the input within the boundary increased production by 6-8% compared to the current relative distribution, increasing production in the food-insecure countries by two-thirds. Our findings provide georeferenced guidelines for redistributing nitrogen use to enhance food security while safeguarding the planet.

Optimizing the Mulching Pattern and Nitrogen Application Rate to Improve Maize Photosynthetic Capacity, Yield, and Nitrogen Fertilizer Utilization Efficiency.

Residual film pollution and excessive nitrogen fertilizer have become limiting factors for agricultural development. To investigate the feasibility of replacing conventional plastic film with biodegradable plastic film in cold and arid environments under nitrogen application conditions, field experiments were conducted from 2021 to 2022 with plastic film covering (including degradable plastic film (D) and ordinary plastic film (P)) combined with nitrogen fertilizer 0 (N0), 160 (N1), 320 (N2), and 480 (N3) kg·ha-1. The results showed no significant difference (p > 0.05) in dry matter accumulation, photosynthetic gas exchange parameters, soil enzyme activity, or yield of spring maize under degradable plastic film cover compared to ordinary plastic film cover. Nitrogen fertilizer is the main factor limiting the growth of spring maize. The above-ground and root biomass showed a trend of increasing and then decreasing with the increase in nitrogen application level. Increasing nitrogen fertilizer can also improve the photosynthetic gas exchange parameters of leaves, maintain soil enzyme activity, and reduce soil pH. Under the nitrogen application level of N2, the yield of degradable plastic film and ordinary plastic film coverage increased by 3.74~42.50% and 2.05~40.02%, respectively. At the same time, it can also improve water use efficiency and irrigation water use efficiency, but it will reduce nitrogen fertilizer partial productivity and nitrogen fertilizer agronomic use efficiency. Using multiple indicators to evaluate the effect of plastic film mulching combined with nitrogen fertilizer on the comprehensive growth of spring maize, it was found that the DN2 treatment had the best complete growth of maize, which was the best model for achieving stable yield and income increase and green development of spring maize in cold and cool irrigation areas.

A Systematic Review on Effects of Nitrogen Fertilizer Levels on Cabbage (Brassica oleracea var. capitata L.) Production in Ethiopia.

Cabbage (Brassica oleracea var. capitata L.) holds significant agricultural and nutritional importance in Ethiopia; yet, its production faces challenges, including suboptimal nitrogen fertilizer management. The aim of this review was to review the possible effect of nitrogen fertilizer levels on the production of cabbage in Ethiopia. Nitrogen fertilization significantly influences cabbage yield and quality. Moderate to high levels of nitrogen application enhance plant growth, leaf area, head weight, and yield. However, excessive nitrogen levels can lead to adverse effects such as delayed maturity, increased susceptibility to pests and diseases, and reduced postharvest quality. In Ethiopia, small-scale farmers use different nitrogen levels for cabbage cultivation. In Ethiopia, NPSB or NPSBZN fertilizers are widely employed for the growing of various crops such as cabbage. 242 kg of NPS and 79 kg of urea are the blanket recommendation for the current production of cabbage in Ethiopia. The existing rate is not conducive for farmers. Therefore, small-scale farmers ought to utilize an optimal and cost-effective nitrogen rate to boost the cabbage yield. Furthermore, the effectiveness of nitrogen fertilization is influenced by various factors including the soil type, climate, cabbage variety, and agronomic practices. Integrated nutrient management approaches, combining nitrogen fertilizers with organic amendments or other nutrients, have shown promise in optimizing cabbage production while minimizing environmental impacts. The government ought to heed suggestions concerning soil characteristics such as the soil type, fertility, and additional factors such as the soil pH level and soil moisture contents.

Impacts of High-Frequency Chicken Manure Biochar Application on N2O and CH4 Emissions from Vegetable Field in Subtropical China

Vegetable production in Subtropical China is distinguished by excessive nitrogen (N) fertilization, frequent irrigation, and multiple crop rotations in a single year. The aforementioned variables are closely related to soil nitrous oxide (N2O) and methane (CH4) emissions. Hence, we conducted a field trial to measure N2O and CH4 emissions using static chamber–gas chromatograph. Four treatments were used: control (CK) with no fertilizer, 100% chemical N fertilization (CN), the conventional 30% chicken manure N plus 70%CN (CMN + CN), and 30% chicken manure biochar N plus 70%CN (CMBN + CN). The annual cumulative N2O emissions reached 12.4, 63.5, 111.8, and 44.1 kg N2O-N ha−1 for the CK, CN, CMN + CN, and CMBN + CN treatments, respectively. Compared to the CN and CMN + CN treatments, the CMBN + CN treatment reduced N2O emissions by 35.9%–65.7%, while it simultaneously increased the total vegetable yield by 16.1% compared to the CN treatment. Seven seasons mean N2O emission factors are 1.3% for CN, 3.8% for CMN + CN, and 0.9% for CMBN + CN. The CH4 emission was negligible, ranging from 0.07 kg CH4-C ha−1 for the CK treatment to 0.8 kg CH4-C ha−1 for the CN treatment. N2O emissions peaked under the conditions of an interior chamber temperature of around 31.9 °C and the water-filled pore space (WFPS) of the soil being approximately 60%. Future climate change will intensify, triggering higher N2O emissions from subtropical vegetable fields. CMB can be one of the best substitutes for direct chicken manure application as a soil supplement because it has a beneficial effect on improving vegetable yield and reducing N2O emissions in Subtropical China.

Laser ablation of thin SiN x layer coated on silicon wafer—evaluation of process performance for PERC solar cell application

In fabricating passivated emitter and rear contact (PERC) solar cells, creating small openings on the SiN x coated silicon substrate to establish metal contacts necessitates using a nanosecond pulsed green laser for ablation. However, the thermal nature of laser ablation poses a challenge. Excessive nitrogen diffusion from SiN x into the silicon substrate can compromise the electrical performance of solar cells. Therefore, this study aims to comprehensively understand how laser parameters impact the electrical properties of such solar cells. PERC solar cell precursors were initially fabricated by ablating the SiN x layer at four laser fluences, each corresponding to different regimes: solid, liquid, vapor, and phase explosion. Subsequently, various optical, chemical, and electrical characterizations were conducted on the solar cell precursors. Complete PERC solar cells were also fabricated to measure quantum efficiency (QE). In the solid regime, SiN x removal is precise, with minimal thermal damage, resulting in a nitrogen concentration of approximately 0.15%. Photoluminescence count and carrier lifetime are notably higher by 21% in the solid regime compared to the explosive regime. The QE measurement at 984 nm quantitatively assesses rear-side recombination losses. Notably, 26% of the area exhibits a 56% QE in the solid state, while this number drops to around 22% in the explosive state. This decline can be attributed to increased thermal damage in the explosive regime, which augments recombination centers and diminishes the solar cell performance. PERC solar cells ablated in the solid regime showcase lower subsurface damage, superior electrical characteristics, and higher performance than those ablated in the explosive regime.

Reducing livestock quantities to avoid manure nitrogen surplus: would meat self-sufficiency be met in eastern regions of China?

In building a sustainable food system, the management of livestock production should avoid nitrogen (N) surplus and ensure animal-sourced food self-sufficiency. Reducing livestock quantities in regions producing excess of animal-sourced food and livestock manure is an effective approach for mitigating manure N surplus. In this study, we considered the eastern regions of China as a case study to quantitatively analyze whether meat self-sufficiency could be met when reducing the livestock quantity to avoid manure N surplus. In addition to considering the baseline scenario, considering the current livestock quantity (scenario C), we defined three strategies corresponding to livestock reduction scenarios: taking meat self-sufficiency as a priority regardless of the manure balance (scenario TB); taking manure N surplus avoidance as a priority regardless of the meat balance (scenario MNB); and considering the most limiting conditions between satisfying meat self-sufficiency and avoiding manure N surplus (scenario LF). A balance index was used to describe the excess (i.e., positive value) or deficiency (i.e., negative value) of meat and manure N. Concerning the whole of eastern China, in scenario LF, the meat balance index (TBI) and manure N balance index (MNBI) were 0.25 and −0.39, respectively, which could satisfy meat demand while avoid manure N surplus (for scenarios C, TB, and MNB, the TBIs were 1.95, 0, and 1.09, and the MNBIs were 0.56, −0.48, and 0, respectively). At the regional level, the regions with meat self-sufficiency accounted for more than 70% in the LF scenario, and manure N surplus could be avoided in all regions. However, southwestern China should adopt further measures, such as trading among adjacent regions and increasing manure fertilizer application, to satisfy the meat demand while avoiding surplus manure N.

Current water pollution status at an important wintering site of the black-faced spoonbill Platalea minor in Xinghua Bay, south China

Xinghua Bay is one of the largest wintering sites of the black-faced spoonbill Platalea minor in mainland China. The ecosystem of Xinghua Bay has shown a deteriorating trend with the increasing pressure of economic development in recent decades. To understand the current conservation status of the wintering spoonbills in Xinghua Bay, we collected water samples along the coast of Xinghua Bay and important spoonbill habitats during the wintering period to analyze the pollution degree of 7 target heavy metals and organics. The Nemerow pollution index (NPI), heavy metal pollution index (HPI) and contamination degree (CD) were used to assess the heavy metal pollution levels. The ecological risk index of a target heavy metal (Efi) and potential ecological risk index of all target heavy metals (RI) were used to assess the ecological risk of heavy metals levels in Xinghua Bay. Positive matrix factorization (PMF) was used to determine the sources of heavy metals in coastal waters with the EPA PMF5.0 model. The results showed that there was moderate to very heavy pollution by heavy metals and moderate associated ecological risks in Xinghua Bay, in which Hg and Cd were the major heavy metal pollution sources, and the level of organic pollution was of serious concern. The use of fertilizers for cultured shellfish and aquaculture in and around the bay were the major cause of the excessive nitrogen and phosphorus levels, and factories surrounding Xinghua Bay were the major sources of heavy metals and organic pollution. We propose conservation measures to increase black-faced spoonbill population and enhance its habitats.

One-Time Contact Application of Controlled-Release Urea and Optimized Method Improved Rice Yield and Nitrogen Use Efficiency with 50% Nitrogen Input

Excessive nitrogen application is a common phenomenon in rice production in China, which will lead to a low nitrogen utilization rate and increase farmers’ production costs. In Jingzhou, Hubei Province, for two consecutive years (2021, 2022), rice was planted with nursery-box total fertilization (NBTF) technology to provide technical support for rice seedling box contact fertilization technology. The results showed that, compared with the conventional treatment, the seedling emergence rate decreased by 7.70–11.87%, but the seedling quality significantly improved and the plant height significantly increased by 4.38–6.06% in the full-heading stage after the aforementioned treatments. The leaf area index significantly increased by 16.75–34.55%, 10.04–19.30%, and 12.13–18.60% in the tiller, booting, and full-heading stages, respectively, whereas the photosynthetic rate significantly increased by 3.80–5.25% in the booting stage. The rice yield under the 50% CRU and 50% CRU + S treatments was the same as that under the FFP treatment. The rice yield under 50% CRU + BT and 50% CRU + BT + S treatments was 7.50–10.61% higher than that under the FFP treatment; nitrogen partial factor productivity increased by 96.15–123.63%. NBTF combined with Boxingtanzhuang (in Chinese) seedling trays showed an increase in yield, whereas normal seedling trays showed a stable yield. It is suggested that the seedling tray and fertilizer should be specialized in the rice seedling box, and the height of the seedling tray should be increased by 3–5 cm. At the same time, special controlled-release urea should be selected to ensure less N release before emergence and improve the seedling emergence rate so as to popularize NBTF technology in a large area.

Mapping lock-ins and enabling environments for agri-food sustainability transitions in Europe

European agri-food systems must overcome structural lock-ins to achieve more sustainable modes of production and consumption. Yet European regions are highly diverse, and we lack understanding of how different regional characteristics may enable or inhibit sustainability transitions. This hinders the development of context-tailored governance strategies. In this paper, we identify and apply sets of spatial indicators to map the regional potentials for agri-food transitions. We first analyse the strength of lock-in to the incumbent agro-industrial paradigm. We then map the enabling environments for two alternative agri-food networks—multifunctional value chains and civic food networks—that each embed distinct social–ecological qualities of agriculture and food. Results demonstrate a large spatial diversity in transition potential, with stronger lock-ins throughout North and Western Europe and stronger enabling environments for agri-food transitions in Italy, France, Switzerland, and Southwest Germany. We find that lock-ins are strongest in livestock-dominated regions and are associated with higher GHG emissions and excess nitrogen levels. Our study demonstrates the need for coordinated public policies that (1) leverage region-specific transition potentials and (2) enable complementary innovations in market-based and community-led networks.

Using milk mid-infrared spectroscopy to estimate cow-level nitrogen efficiency metrics

Minimizing pollution from the dairy sector is paramount; one potential cause of such pollution is excess nitrogen. Nitrogen pollution contributes to a deterioration in water quality as well as an increase in both eutrophication and greenhouse gases. It is therefore essential to minimize the loss of nitrogen from the sector, including excretion from the cow. Breeding programs are one potential strategy to improve the efficiency with which nitrogen is used by dairy cows but relies on routine access to individual cow information on how efficiently each cows uses the nitrogen it ingests. A total of 3,497 test-day records for individual cow nitrogen efficiency metrics along with milk yield and the associated milk spectra were used to investigate the ability of milk infrared spectral data to predict these nitrogen traits; both traditional partial least squares regression and neural networks were used in the prediction process. The data originated from 4 farms across 11 years. The nitrogen traits investigated were nitrogen intake, nitrogen use efficiency, and nitrogen balance. Both nitrogen use efficiency and nitrogen balance were calculated considering nitrogen intake, nitrogen in milk, nitrogen in the conceptus, nitrogen used for the growth, nitrogen stored in the reserves, and nitrogen mobilized from the reserves. Irrespective of the nitrogen-related trait being investigated, the best prediction from 4-fold cross-validation were achieved using neural networks that considered both the morning and evening milk spectra along with milk yield, parity, and days in milk in the prediction process. The coefficient of determination in the cross-validation was 0.61, 0.74, and 0.58 for nitrogen intake, nitrogen use efficiency, and nitrogen balance, respectively. In a separate series of validation approaches, the calibration and validation was stratified by herd (n = 4) and separately by year. For these scenarios, partial least squares regression generated more accurate predictions compared with neural networks; the coefficient of determination was always lower than 0.29 and 0.60 when validation was stratified by herd and year, respectively. Therefore, if the variability of the data being predicted in the validation data sets is similar to that in the data used to develop the predictions, then nitrogen-related traits can be predicted with reasonable accuracy. In contrast, where the variability of the data that exists in the validation data set is poorly represented in the calibration data set, then poor predictions will ensue.

Integrating plant morphological traits with remote-sensed multispectral imageries for accurate corn grain yield prediction.

Sustainable crop production requires adequate and efficient management practices to reduce the negative environmental impacts of excessive nitrogen (N) fertilization. Remote sensing has gained traction as a low-cost and time-efficient tool for monitoring and managing cropping systems. In this study, vegetation indices (VIs) obtained from an unmanned aerial vehicle (UAV) were used to detect corn (Zea mays L.) response to varying N rates (ranging from 0 to 208 kg N ha-1) and fertilizer application methods (liquid urea ammonium nitrate (UAN), urea side-dressing and slow-release fertilizer). Four VIs were evaluated at three different growth stages of corn (V6, R3, and physiological maturity) along with morphological traits including plant height and leaf chlorophyll content (SPAD) to determine their predictive capability for corn yield. Our results show no differences in grain yield (average 13.2 Mg ha-1) between furrow-applied slow-release fertilizer at ≥156 kg N ha-1 and 208 kg N ha-1 side-dressed urea. Early season remote-sensed VIs and morphological data collected at V6 were least effective for grain yield prediction. Moreover, multivariate grain yield prediction was more accurate than univariate. Late-season measurements at the R3 and mature growth stages using a combination of normalized difference vegetation index (NDVI) and green normalized difference vegetation index (GNDVI) in a multilinear regression model showed effective prediction for corn yield. Additionally, a combination of NDVI and normalized difference red edge index (NDRE) in a multi-exponential regression model also demonstrated good prediction capabilities.

Response of nutrient accumulation, remobilization and yield to combined application of nitrogen and potassium in waxy maize

Unbalanced fertilizers supply with highly intensity and excessive nitrogen (N) and less potassium (K), lead to the decrease of soil fertility year by year. Balanced fertilization is one of the most effective measures to reduce fertilizer use while improving maize yield and efficiency. Two N levels (180 and 225 kg N ha−1, abbreviated N12 and N15) and four K treatments (0, 75, 150, and 75+75 kg K2O ha−1, abbreviated K0, K5, K10, and K5+5) were set to study the effects of combined application of N and K on the biomass and nutrient accumulation and remobilization characteristics in waxy maize. The results demonstrated that grain yield increased when higher amounts of K were applied at constant N levels, showing an average increase of 1,254.8 kg ha−1 (2020) and 727.3 kg ha−1 (2021) compared with K0. Under same N and K application, K5+5 increased grain yield by increasing kernel weight. Under K5+5 treatment, the biomass and nutrient accumulation had no significant difference between N12 and N15. Compared with K10, K5+5 not only enhanced the average remobilization amount (RBA) of biomass, but also increased RBA of N, phosphorus (P) and K. In addition, the average remobilization efficiency (RBE) of biomass, N, P and K in K5+5 were increased 3.3, 4.6, 10.6 and 4.2%, respectively. Furthermore, topdressing K improved the apparent contribution to grain (AC) of biomass, N, P and K, which promoted more nutrient to grains, and significantly increased nutrient harvest index. Considering yield and fertilizer use efficiency, we recommend optimized K application (basal and topdressing 75 kg ha−1) and moderately reduced N application (from 225 to 180 kg ha−1) in the production of spring-sown waxy maize in southern China.

Defining the maximum nitrogen surplus in water management plans to recover nitrate polluted aquifers in Spain

Nitrate pollution in aquifers is a global concern. Spain has developed a national strategy to recover nitrate polluted aquifers aligned with the European Union (EU) policies, specifically through the water planning under the EU Water Framework Directive. River basin management plans use PATRICAL model results to define the maximum nitrogen surplus in each polluted aquifer for the first time. The maximum nitrogen surplus allows to reach the good status in each aquifer and the model provides the number of years required.Around 30% of the aquifers in Spain is currently heavily polluted by nitrates. Model results show that 90% of these aquifers can be recovered in next 6–12 years by increasing nitrogen use efficiency and reducing nitrogen losses around 50%, which is in line with the EU Farm to Fork Strategy. The remaining aquifers require additional reductions to achieve the good status. In Spain this increase in nitrogen efficiency can be obtained with different measures including 30% reduction of current fertilization.

Correlation Studies of Growth and Yield Attributes with Grain Yield of Scented Rice as Influenced by Nano Urea in Combination with Inorganic Fertilizer and Organic Manure

Appropriate nitrogen management increases the yield of rice. Both excess and low nitrogen content leads to lower the production of rice. A large amount of nitrogen causes soil fertility loss and thus, the yield. Nano urea is a nano technology that provides nitrogen required for crop at critical stages. Keeping these in mind a research experiment was carried out to assess the correlation studies of growth and yield attributes with grain yield of scented rice as influenced by Nano urea in combination with inorganic fertilizer and organic manure at Instructional Farm Unit, Krishi Nagar, JNKVV, Jabalpur during the rainy season of 2022 and 2023. Ten treatment combinations were laid out in randomized block design with four replications. The results revealed that all the growth parameters were observed a strong and positive correlation with grain yield of rice. The regression analysis showed a strong positive linear relationship with the growth parameters viz., plant height (95% and 97%, respectively) and no. of tillers hill-1 (94% and 91%, respectively), yield attributes viz., panicle length (94% and 95%, respectively) and total no. of grains panicle-1 (97% and 95%, respectively) and grain yield of rice. This concludes that all the growth and yield attributes positively contributed towards gaining higher yield.

Water and nitrogen footprint assessment of integrated agronomic practice management in a summer maize cropping system

The footprints of water and nitrogen (WF and NF) provide a comprehensive overview of the type and quantity of water consumption and reactive nitrogen (Nr) loss in crop production. In this study, a field experiment over two years (2019 and 2020) compared three integrated agronomic practice management (IAPM) systems: An improved management system (T2), a high-yield production system (T3), and an integrated soil–crop management system (ISCM) using a local smallholder farmer's practice system (T1) as control, to investigate the responses of WF, Nr losses, water use efficiency (WUE), and nitrogen use efficiency (NUE) to IAPM. The results showed that IAPM optimized water distribution and promoted water use by summer maize. The evapotranspiration over the whole maize growth period of IAPM increased, but yield increased more, leading to a significant increase in WUE. The WUE of the T2, T3, and ISCM treatments was significantly greater than in the T1 treatment, in 2019 and 2020 respectively, by 19.8–21.5, 31.8–40.6, and 34.4–44.6%. The lowest WF was found in the ISCM treatment, which was 31.0% lower than that of the T1 treatment. In addition, the ISCM treatment optimized soil total nitrogen (TN) distribution and significantly increased TN in the cultivated layer. Excessive nitrogen fertilizer was applied in treatment T3, producing the highest maize yield, and resulting in the highest Nr losses. In contrast, the ISCM treatment used a reduced nitrogen fertilizer rate, sacrificing grain yield partly, which reduced Nr losses and eventually led to a significant increase in nitrogen use efficiency and nitrogen recovery. The Nr level in the ISCM treatment was 34.8% lower than in the T1 treatment while NUE was significantly higher than in the T1 treatment by 56.8–63.1% in 2019 and 2020, respectively. Considering yield, WUE, NUE, WF, and NF together, ISCM should be used as a more sustainable and clean system for sustainable production of summer maize.

Increasing food and feed self-sufficiency and avoiding manure N surplus in eastern regions of China through a spatial crop-livestock optimisation model

CONTEXTAs the largest emerging economy globally, China is facing crop-livestock disconnection, which causes unnecessary synthetic fertiliser use, local food and feed unsatisfied demand, and manure nitrogen (N) surplus. OBJECTIVEWe investigated how crop-livestock regional integration combined with inter-regional transportation of food, feed, and manure, can contribute to food self-sufficiency of easter China (whole and regional level) while avoiding manure N excess. We also investigated how this could increase the local soybean production without harming the self-sufficiency of other food commodities. METHODSWe proposed an optimisation model of integrated crop-livestock production in eastern China, including the production of food, feed, and livestock manure N in each region and the demand for food (according to healthy diet recommendations), feed and manure N. We optimised the supplier cost-benefit balance considering food and feed production, domestic transportation, and foreign trade, taking food and feed demand satisfaction and manure N surplus avoidance as constraints. This optimisation exercise was performed under different scenarios: optimisation without soybean subsidies (scenario O), optimisation with increasing soybean subsidies (scenario OS+). The two scenarios were compared with the baseline scenario B (non-optimised without soybean subsidies) using balance indices (BI, the gap between production and demand divided by demand) of food, feed, and manure N and transportation indices. RESULTS AND CONCLUSIONSResults showed that, for the whole of eastern China, BI were positive for cereals (1.523), vegetables (2.789), meat (0.002), eggs (0.002), milk (0.102), and maize (0.244), and negative for manure N (−0.016) in scenario O. This indicated that most of the food and feed items except soybean were self-sufficient and manure N surplus was avoided after optimisation. Some regions lowered their self-sufficiency for some commodities. As soybean subsidies increased from 0 Yuan ‧ ton-‍1 to 6000 Yuan ‧ ton−1, the BI of soybeans increased by 66.37%. SIGNIFICANCEOur results suggested that crop and livestock can be integrated in China for an improved level of food self-sufficiency and manure N surplus avoidance. However, regional self-sufficiency could not be achieved in all regions for all items, and transportation is necessary. In particular, three strategies seem relevant for policy-making: (i) decreasing livestock quantity, for strengthening feed self-sufficiency and avoiding manure N surplus; (ii) increasing soybean production through subsidies; (iii) reducing regional-level self-sufficiency and increasing the transportation for meat and eggs, which would avoid manure N surplus in densely populated regions, while decreasing the maize transportation.