Overuse Of Nitrogen Research Articles

Nitrogen use efficiency and yield components of rice as influenced by reducing nitrogen application under salinity conditions in a pot experiment

Salinity and overuse of nitrogen (N) fertilizers are two major environmental concerns for rice cultivation that make improving nitrogen use efficiency (NUE) and yield under saline conditions indispensable. However, little is known about NUE during the reproductive stage or rice yield under both salt stress and low N input. This study evaluated the effects of reduced nitrogen on NUE, yield and its components for rice grown in saline soil. A pot experiment was conducted with four N and three NaCl levels using four rice cultivars. High salinity nullified the effects of N on the rice growth and grain yield (GY). By increasing N levels, N efficiency for GY was 15.09, 6.82, and 1.94 under non-saline, moderate, and high salinity levels, respectively. Under moderate salinity, most measured parameters including shoot dry weight (SDW), shoot N content at active tillering (SNC), effective panicle number (EPN) and GY increased significantly with N levels, but to a lesser extent than those of plants grown under non-saline conditions. Regardless of salinity level, increasing N levels significantly reduced agronomical NUE (agNUE) at active tillering, but neither at heading nor at maturity. Under saline conditions, agNUE was strongly and positively correlated with absorption NUE (0.90 and 0.97, p < 0.001) and with a lesser extent to physiological NUE (0.67 and 0.62, p < 0.05) under moderate and severe salinity, respectively during active tillering. Therefore, the improvement in N uptake during active tillering should be investigated as a way to enhance the NUE, EPN, and GY of rice grown in saline conditions.

Feeding the world sustainably: efficient nitrogen use.

Globally, overuse of nitrogen (N) fertilizers in croplands is causing severe environmental pollution. In this context, Gu et al. suggest environmentally friendly and cost-effective N management practices and Hamani et al. highlight the use of microbial inoculants to improve crop yields, while reducing N-associated environmental pollution and N-fertilizer use.

The Contribution of Agronomic Management to Sustainably Intensify Egypt’s Wheat Production

In Egypt, recent shortfalls in the wheat supply from Russia and Ukraine have necessitated substantial increases in domestic production. As agricultural practices influence the yield of bread wheat, we assessed current production strategies in the wheat-based systems of Egypt and investigated their effects on wheat productivity in four study areas in the Nile Delta. We used a multi-stage random sampling technique to select 246 wheat-producing farmers and applied structured questionnaires to assess farming practices and crop performance attributes. Data were analyzed by using descriptive statistics, analysis of variances, and multiple regression models. Wheat farmers were on average 56 years old with about 30 years of farming experience. Land holdings were rather small, with an average of 1.05 hectares and a mean wheat yield of 6.4 metric tons (t)/hectare (ha). Farmers devote &lt;20% of their cropland area to wheat. Of the large observed variation in wheat yield (4.2–8.5 t/ha), 59% was explained by differences in applied cropping practices in the multiple regression model. The application of mineral fertilizers was mostly inappropriate and unbalanced, with an overuse of nitrogen and phosphorus, the complete absence of potassium and micronutrient fertilizers, and insufficient rates of applied organic amendments. The type of the preceding summer crop and the irrigation frequency were found to be the most influencing factors, explaining 7.5% and 38% of the variation in wheat yields. The majority of farmers with low wheat yields irrigated their crops twice per season, while only 7% of high-yielding farmers applied the recommended irrigation frequency of &gt;5 times per season. Most farmers had poor knowledge of modern agronomic practices and inadequate access to information. To enhance domestic production in Egypt, there is a need for fiscal incentives, permitting or stimulating wheat-producing farmers to devote larger shares of their cropland to wheat cultivation. In addition, policies must enable wheat producers to improve their productivity by implementing adequate and sustainable agricultural practices such as crop rotations, balanced mineral nutrient supply, and the use of organic amendments. However, the most important factors are interventions and technologies that improve provision and increase the use efficiency of irrigation water.

Optimizing nitrogen and water management for sustainable greenhouse vegetable production with less greenhouse gas emissions

Intensive greenhouse vegetable production is considered a major source of greenhouse gas emissions and ammonia volatilization in China because the overuse of nitrogen (N) fertilizers is extremely common. Therefore, the emissions of nitrous oxide (N2O), carbon dioxide (CO2), and ammonia (NH3) from five different fertilizer treatments (conventional practice (CN) and four reduced N rate treatments (synthetic fertilizer, combined without (RN1) or with a nitrification inhibitor (3,4-dimethypyrazole phosphate, DMPP) (RN1 +DMPP), and a mixed application of synthetic and organic fertilizers, combined without (RN2) or with straw (RN2 +S))) were determined during a tomato and melon rotation. The results showed that the CN treatment had high total emissions of N2O (9.81 ± 0.81 kg N ha−1 yr−1) and CO2 (6.43 ± 0.75 kg C ha−1 season−1), which were 2.1–6.5 times and 1.2–1.91 times greater than those of other reduced N treatments, respectively. The annual direct N2O emission factor of the CN treatment was 0.94 %, which was higher than that of the reducing N treatments. The RN1, RN2 and RN2 +S treatments significantly (p < 0.05) decreased NH3 volatilization. The RN1 +DMPP treatment significantly (p < 0.05) increased NH3 volatilization in comparison with the RN1 treatment; however, it reduced the net global warming potentials (GWP) due to decreasing both N2O and CO2 emissions. Reducing the N application rate did not compromise vegetable yields in comparison with the CN treatment, but it significantly decreased the yield-scaled N2O emissions (p < 0.05). The combination of synthetic fertilizer and manure significantly (p < 0.05) increased N2O emissions relative to synthetic fertilizer alone. Compared to the other treatments, the RN1 +DMPP treatment significantly reduced the net GWP. Therefore, RN1 +DMPP is a better practice to reduce greenhouse gas emissions and simultaneously maintain crop yield in intensive vegetable production.

Predicting Nitrogen Efficiencies in Mature Maize with Parametric Models Employing In-Season Hyperspectral Imaging

Overuse of nitrogen (N), an essential nutrient in food production systems, can lead to health issues and environmental degradation. Two parameters related to N efficiency, N Conversion Efficiency (NCE) and N Internal Efficiency (NIE), measure the amount of total biomass or grain produced, respectively, per unit of N in the plant. Utilizing remote sensing to improve these efficiency measures may positively impact the stewardship of agricultural N use in maize (Zea mays L.) production. We investigated in-season hyperspectral imaging for prediction of end-season whole-plant N concentration (pN), NCE, and NIE, using partial least squares regression (PLSR) models. Image data were collected at two mid-season growth stages (V16/V18 and R1/R2) from manned aircraft and unmanned aerial vehicles for three site years of 5 to 9 maize hybrids grown under 3 N treatments and 2 planting densities. PLSR models resulted in accurate predictions for pN at R6 (R2 = 0.73; R2 = 0.68) and NCE at R6 (R2 = 0.71; R2 = 0.73) from both imaging times. Additionally, the PLSR models based on the R1 images, the second imaging, accurately distinguished the highest and lowest ranked hybrids for pN and NCE across N rates. Neither timepoint resulted in accurate predictions for NIE. Genotype selection efficiency for end-season pN and NCE was increased through the use of the in-season PLSR imaging models, potentially benefiting early breeding screening methods.

OsNPF3.1, a member of the NRT1/PTR family, increases nitrogen use efficiency and biomass production in rice

The overuse of nitrogen (N) fertilizer in fields has increased production costs and raised environmental concerns. Increasing the N use efficiency (NUE) of rice varieties is crucial for sustainable agriculture. Here we report the cloning and characterization of OsNPF3.1, a gene that controls rice NUE. An amino acid mutation in the OsNPF3.1 coding region caused different NUEs in wild and cultivated rice. OsNPF3.1, which is expressed mainly in the aerial parts of rice, also affects rice plant height, heading date, and thousand-grain weight. The OsNPF3.1 protein is located in the plasma membrane. When OsNPF3.1 was subjected to artificial selection, two naturally varying loci were associated with NUE, of which OsNPF3.1Chr6_8741040 differed between indica and japonica rice. OsNPF3.1 can be used as a new target gene for breeding rice varieties with high NUE.

Can Seaweed Extract Improve Yield and Quality of Brewing Barley Subjected to Different Levels of Nitrogen Fertilization?

Barley is the primary matrix for malting process of beer production. Farmers count on increasing cultivation inputs, especially nitrogen fertilization, in order to reach a higher yield. Nevertheless, an overuse of nitrogen, besides causing environmental damages, can determine a deterioration of quality traits of malting barley, in particular an increase in grains protein content, which should range between 10 and 11% as required by the mating industry. Over two successive years, barley was grown under 4 different nitrogen (N) doses—0 kg N ha−1—N0; 20 kg N ha−1—N20; 40 kg N ha−1—N40 and 60 kg N ha−1—N60, and subject to a biostimulant treatment (Ecklonia maxima seaweed extract). Barley yield and growth parameters increased with nitrogen and seaweed application. N40 was already sufficient in the second year to reach the plateau of the highest production. Biostimulant application increased 17.9% the nitrogen use efficiency, 15.7% the biomass production, and 17.0% the yield with respect to untreated plants. Our results indicate that a significant reduction in nitrogen is possible and desirable, combined with the application of a plant-based biostimulant like seaweed extract, which determines an improvement in nitrogen use efficiency, assuring a higher production and lower fertilization inputs.

Improved economic and environmental outcomes from targeted fertilizer policy.

The overuse of nitrogen (N) fertilizer for wheat is a serious problem in China, and previous studies seldom distinguish between the use of basal and topdressing N fertilizer. Data from 225 households in Jiangsu Province, China (a wheat planting area), were collected through face-to-face interviews with each head of the household. Regression models were used to study factors affecting farmers' application of basal and topdressing N fertilizers separately. Fertilizer retailers proposed fertilizer application levels that were in opposition to their concern for the environment. Farmers' concern for the environment only affected their application of topdressing N fertilizer and had no significant influence for use of total N fertilizer. The farmland area and amount of experience planting wheat had negative effects on basal N fertilizer use, but not on topdressing fertilizer. In the study area, the optimal strategy for decreasing N fertilizer application is designing policies to rent more farmlands to farmers with the most experience first. These farmers with their higher farm income would decrease basal N fertilizer use and the basal-topdressing ratio to improve N fertilizer use efficiency and then decrease the N fertilizer leaching into the environment.

Impact of controlled-release urea on rice yield, nitrogen use efficiency and soil fertility in a single rice cropping system

Overuse of nitrogen (N) fertilizer has led to low N use efficiency (NUE) and high N loss in single rice cropping systems in southeast China. Application of controlled-release urea (CRU) is considered as an effective N fertilizer practice for improving crop yields and NUE. Here, field experiments were conducted during 2015–2017 to assess the effects of two CRUs (resin-coated urea (RCU) and polyurethane-coated urea (PCU)) on rice yields, NUE and soil fertility at two sites (Lincheng town (LC) and Xintang town (XT)). Four treatments were established at each site: (1) control with no N application (CK), (2) split application of conventional urea (U, 270 kg N ha−1), (3) single basal application of RCU (RCU, 216 kg N ha−1), and (4) single basal application of PCU (PCU, 216 kg N ha−1). The N application rate in the CRU treatment compared to the U treatment was reduced by 20%. However, the results showed that, compared to split application of urea, single basal application of CRU led to similar rice grain yields and aboveground biomass at both sites. No significant difference in the N uptake by rice plant was observed between the U and CRU treatments at either site. There were no significant differences in the N apparent recovery efficiency (NARE) among the U, RCU and PCU treatments, with the exception of that in XT in 2015. Compared to application of U, application of CRU increased the N agronomic efficiency (NAE) and N partial factor productivity (NPFP) by 17.4–52.6% and 23.4–29.8% at the LC site, and 15.0–84.1% and 23.2–33.4% at the XT site, respectively, during 2015–2017. Yield component analysis revealed that greater rice grain yield in response to N fertilizer was attributed mainly to the number of panicles per m2, which increased in the fertilized treatments compared to the CK treatment. The application of CRU did not affect the soil fertility after rice harvest in 2016. Overall, these results suggest that single basal application of CRU constitutes a promising alternative N management practice for reducing N application rates, time- and labor-consuming in rice production in southeast China.

How to increase maize production without extra nitrogen input

Increasing crop yields while reducing environmental impacts are a great challenge to ensuring food security and environmental quality for the world agriculture. Increasing planting density appropriately is one of the most effective strategies for increasing maize (Zea mays L.) yield. In China, overuse of nitrogen (N) fertilization on maize has resulted in excessive N surplus in the soil and environmental impacts. To address this challenge we conducted 212 site-year field experiments at two planting densities of 60000 and 75000 plants per ha with the same inputs of N. Results showed that maize yield could be increased 5.59% across China and 10.5%, 2.7%, 5.2% and 10.3% respectively in Southwest (SW), Huanghuaihai (HM), North (NM) and Northwest (NW) maize regions without extra inputs of N. The Life-cycle assessment showed that reactive N loss intensity and GHG intensity decreased by 2.2% to 10.2% across different regions of China, indicating that yield increase could be achieved without extra N inputs and further negative environmental impacts if planting density was increased by 15000 plants per ha under the current condition of excessive N surplus in China. If farmers in China increase maize planting density by 15000 per ha across the whole country the total maize production from the same planting area of 2017 would be 290 Mt which will be close to the expected demand of 315 Mt by 2030 while reducing the environmental impacts of intensive agriculture.

Effectiveness of dicyandiamide as a nitrification inhibitor in biochar-amended soil

Overuse of nitrogen (N) fertilizers may lead to many environmental issues via N leaching into groundwater and agricultural runoff into surface water. Biochar, a sustainable soil amendment agent, has been widely studied because of its potential to retain moisture and nutrients. However, recent studies have shown that biochar has a very limited ability to improve the retention of negatively charged nitrite (NO−2) or nitrate (NO−3). Although positively charged ammonium (NH+4) can be better held by biochar, it is usually susceptible to nitrification and can be easily transformed into highly mobile NO−2 and/or NO−3. In practice, dicyandiamide (DCD) has been used to inhibit nitrification, preserving N in its relatively immobile form as NH+4. Therefore, it is likely that the effects of DCD and biochar in soils would be synergistic. In this study, the influences of biochar on the effectiveness of DCD as a nitrification inhibitor in a biochar-amended soil were investigated by combining the experimental results of incubation, adsorption isotherm, and column transport with the simulated results of different mathematical models. Biochar was found to stimulate the degradation of DCD, as the maximum degradation rate slightly increased from 1.237 to 1.276 mg kg−1 d−1 but the half-saturation coefficient significantly increased from 5.766 to 9.834 mg kg−1. Considering the fact that the availability of DCD for nitrification inhibition was continuously decreasing because of its degradation, a novel model assuming non-competitive inhibition was developed to simulate nitrification in the presence of a decreasing amount of DCD. Depending on the environmental conditions, if the degradation of DCD and NH+4 in biochar-amended soil is not significant, improved contact due to the mitigated spatial separation between NH+4 and DCD could possibly enhance the effectiveness of DCD.

Crop production in Pakistan and low nitrogen use efficiencies

Overuse of nitrogen (N) fertilizer, a crucial productivity factor in world cropping systems, is detrimental to the sustainability of crop production from an economic and environmental perspective. Mean yield, N fertilizer use, partial factor productivity (PFP) of N, N use efficiency (NUE) and N surplus in wheat, cotton and rice production in Pakistan, which account for 75% of total national fertilizer N use, were compared with those for the top producer countries for 2014. Pakistan was among the top four in terms of N use but had low mean yields, with the lowest PFP and NUE and highest N surplus. During 1961–2014 in Pakistan, N fertilizer use and N surplus grew at a much faster pace than mean yields; however, PFP and NUE continued to decline to much lower levels. The great potential for Pakistan to increase NUE lies in agronomic practices other than increasing N fertilization, such as balanced crop nutrition, irrigation management, inclusion of legumes in crop rotations, precision in-season N management and the use of enhanced efficiency fertilizers, as is the case for many other parts of the world. Nitrogen is critical to crop production but its overuse challenges sustainability. This study finds that, despite intense and growing nitrogenous fertilizer use, Pakistan’s crop yields have risen much more slowly than expected.

Impact of nitrogen fertilization on soil respiration and net ecosystem production in maize

Agriculture in the semi-arid is often challenged by overuse of nitrogen (N), inadequate soil water and heavy carbon emissions thereby threatening sustainability. Field experiments were conducted to investigate the effect of nitrogen fertilization levels (N&lt;sub&gt;0&lt;/sub&gt; – 0, N&lt;sub&gt;100&lt;/sub&gt; – 100, N&lt;sub&gt;200&lt;/sub&gt; – 200, N&lt;sub&gt;300&lt;/sub&gt; – 300 kg N/ha) on soil water dynamics, soil respiration (Rs), net ecosystem production (NEP), and biomass yields. Zero nitrogen soils decreased Rs by 23% and 16% compared to N&lt;sub&gt;300&lt;/sub&gt; and N&lt;sub&gt;200&lt;/sub&gt; soils, respectively. However, biomass yield was greatest under N&lt;sub&gt;300&lt;/sub&gt; compared with N&lt;sub&gt;0&lt;/sub&gt;, which therefore translated into increased net primary production by 89% and NEP by 101% compared to N&lt;sub&gt;0&lt;/sub&gt;. To a lesser extent, N&lt;sub&gt;200&lt;/sub&gt; increased net primary production by 69% and net ecosystem production by 79% compared to N&lt;sub&gt;0&lt;/sub&gt;. Grain yields were greatest under N&lt;sub&gt;300&lt;/sub&gt; compared with N&lt;sub&gt;100&lt;/sub&gt; and N&lt;sub&gt;0&lt;/sub&gt;, which therefore translated into increased carbon emission efficiency (CEE) by 53, 39 and 3% under N&lt;sub&gt;300&lt;/sub&gt; compared to N&lt;sub&gt;0&lt;/sub&gt;, N&lt;sub&gt;100&lt;/sub&gt; and N&lt;sub&gt;200&lt;/sub&gt; treatments, respectively. There appears potential for 200 kg N/ha to be used to improve yield and increase CEE.

The shadow price of nitrogen

PurposeThe most recent and prestigious scientific research shows that nitrogen leaching caused by over-used nitrogen fertilizer rapidly acidifies all soil types in China, revolutionizing the basic understanding of the mechanism of soil acidification. The purpose of this paper is to study the impact of nitrogen on soil acidity over the long run, which is the shadow price of nitrogen.Design/methodology/approachIn a discrete dynamic programming model, this paper compares the nitrogen application and soil pH between optimal nitrogen control that takes the shadow price of nitrogen into consideration and myopic nitrogen control that ignores that shadow price. Using a five-year panel experimental data on a rapeseed-rice rotation, this paper simulates and numerically solves the dynamic model.FindingsBoth theoretically and empirically, this paper shows that the over-use of nitrogen and the decline in soil pH are explained by ignorance of the shadow price of nitrogen. Compared with optimal nitrogen control, myopic nitrogen control applies more nitrogen in total, resulting in lower soil pH. In addition, over-use in the first season contributes to soil acidification and the carry-over effects mitigate that problem.Originality/valueThis paper enriches the literature by extending the study of the environmental impact of nitrogen leaching to its impact on the long-term loss in agricultural production, providing a new theoretical framework in which to study soil acidification rather than conventionally treating soil acidification as a secondary consequence of acid rain, and showing the possibility of using nitrogen control to mitigate soil acidification when lime applications are not feasible due to socio-economic constraints.

Assessment of Nitrogen Leaching of Cropping Pattern by Soil Nitrogen Balance Equation (Case Study: Varamin Irrigation and Drainage Network)

Nitrogen is often one of the most important limiting factors for biomass production. Usually few soils have proper amount of nitrogen, so it is usually added by fertilizers. In cropping systems, nitrogen fertilization practices can provide a sufficient nitrogen supply for plants to achieve the potential yield. However, to ensure reaching to this potential yield, farmers often apply more nitrogen fertilizers than the required nitrogen for achieving maximum yield. Nitrogen fertilizer should be given to soil according to nitrogen content of soil, water and crop nitrogen demand during the growth periods. Especially in the lands that apply wastewater and groundwater for irrigation and irrigation sources have large quantities of nitrogen, therefore we Should reduce the amount of fertilizer used in agricultural lands, In other words for planning the plant fertilizer demand, nitrogen balance in soil should be considered. Nitrogen overuse increases the risk of nitrogen leaching to groundwater, contaminating groundwater and threatening the human health. In recent years, critical plant nitrogen concentration equation is used to determine crop nitrogen demand during the different growth stages of plants. The purpose of this study is to determine the nitrogen demand of Varamin network’s cropping pattern by using the critical plant nitrogen concentration equation and comparing the result with the amount of nitrogen fertilizer commonly applied in the study area. In this study, monthly biomass production for growing period was determined based on normalized water productivity index and plant canopy development. Coefficient of critical nitrogen concentration equation for each plant was determined by previous researches. The result of this study showed that for barley, the amount of nitrogen applied in Varamin network is equal to nitrogen demand of the cropsand for wheat, maize and tomato are 25%, 61% and 18%, respectively, higher than the amount obtained from critical plant nitrogen concentration equation.also according to the results of soil Nitrogen balance in lands covered by AU canal of Varamin network, 707 ton of nitrogen entered to soil and groundwater by leaching and we should considered appropriate solutions to reduce leaching, such as using high-yielding crops that remove a significant amount of N in the harvested portion, synchronizing fertilizer application with crop demand, conjunctive use of wastewater and groundwater with proper nitrogen concentration and etc.

The effect of simple nitrogen fertilizer recommendation strategies on product carbon footprint and gross margin of wheat and maize production in the North China Plain

Overuse of nitrogen (N) fertilizer constitutes the major issue of current crop production in China, exerting a substantial effect on global warming through massive emission of greenhouse gas (GHG). Despite the ongoing effort, which includes the promotion of technologically sophisticated N management schemes, farmers' N rates maintain at excessive rates. Therefore the current study tests three simple and easily to apply N fertilizer recommendation strategies, which could be implemented on large scale through the existing agricultural advisory system of China, at comparatively low cost. Building on a detailed crop production dataset of 65 winter wheat (WW) and summer maize (SM) producing farm households of the North China Plain, scenario analysis is applied. The effects of the three N strategies under constant and changing yield levels on product carbon footprint (PCF) and gross margin (GM) are determined for the production condition of every individual farm household. The N fixed rate strategy realized the highest improvement potential in PCF and GM in WW; while the N coefficient strategy performed best in SM. The analysis furthermore revealed that improved N management has a significant positive effect on PCF, but only a marginal and insignificant effect on GM. On the other side, a potential 10% yield loss would have only a marginal effect on PCF, but a detrimental effect on farmers' income. With farmers currently applying excessive N rates as “cheap insurance” against potential N limitation, it will be of vital importance to avoid any yield reductions (caused by N limitation) and respective severe financial losses, when promoting and implementing advanced fertilization strategies. To achieve this, it is furthermore recommended to increase the price of fertilizer, improve the agricultural extensions system, and recognize farmers' fertilizer related decision-making processes as key research areas.

Establishing a regional nitrogen management approach to mitigate greenhouse gas emission intensity from intensive smallholder maize production.

The overuse of Nitrogen (N) fertilizers on smallholder farms in rapidly developing countries has increased greenhouse gas (GHG) emissions and accelerated global N consumption over the past 20 years. In this study, a regional N management approach was developed based on the cost of the agricultural response to N application rates from 1,726 on-farm experiments to optimize N management across 12 agroecological subregions in the intensive Chinese smallholder maize belt. The grain yield and GHG emission intensity of this regional N management approach was investigated and compared to field-specific N management and farmers' practices. The regional N rate ranged from 150 to 219 kg N ha−1 for the 12 agroecological subregions. Grain yields and GHG emission intensities were consistent with this regional N management approach compared to field-specific N management, which indicated that this regional N rate was close to the economically optimal N application. This regional N management approach, if widely adopted in China, could reduce N fertilizer use by more than 1.4 MT per year, increase maize production by 31.9 MT annually, and reduce annual GHG emissions by 18.6 MT. This regional N management approach can minimize net N losses and reduce GHG emission intensity from over- and underapplications, and therefore can also be used as a reference point for regional agricultural extension employees where soil and/or plant N monitoring is lacking.

Promote Sustainable Development for Irrigated Rice Through SSNM Technology in China

Today, the overuse of nitrogen (N) fertilizer and high N loss result in serious nitrate pollution of water and deter the sustainable development of agriculture and social economy. A recently developed site-specific nutrient management (SSNM) can reduce fertilizer-N use while preventing the yield from falling. In this paper, we raise the question of fertilizer N application in rice production through a survey of farmers' practice of fertilizer N in 18 villages of four provinces. The average rate of N application for rice production in the 18 villages was 190 kg/ha, and 76% to 100% of the total fertilizer N which was applied within 10 days after transplanting resulted in lots of nitrate leached into water. Furthermore, we tested the effect of SSNM through farmer participatory trial. The SSNM technology maintained rice yields with significantly less fertilizer N and there was no increase in labor input, as much as 31% fertilizer N were saved with the SSNM technology. Finally, the paper points that extension and further research of the SSNM technology should be an effective method to deal with the contradiction of population, food and nitrate non-point pollution of water resource and promote the sustainability of agriculture.

Farmers' costs of environmental regulation: Reducing the consumption of nitrogen in citrus farming

Environmental externalities in agriculture, and the choice of suitable instruments to integrate environmental concerns into agricultural policies, are a matter of interest for the Common Agricultural Policy. In this paper, we use Data Envelopment Analysis techniques to assess the impact on farms' performance of two environmentally-friendly regulations aimed at abating consumption of inorganic nitrogen in Spanish citrus farming: levies on purchased nitrogen and nitrogen use permits for farms. By comparing farms' short-run maximum profits under both unregulated and regulated scenarios a regulation cost index is computed. Our results show that nitrogen overuse is mostly a matter of management inefficiency and that pollution could be reduced by promoting best farming techniques. Instead, if environmental regulations are implemented, regulating authorities should be aware that quantitative limits exercise a lower impact on farms' profits than taxes.