Reduction Of Fertilizer Application Research Articles

How do price (risk) changes influence farmers’ preferences to reduce fertilizer application?

AbstractThe decision of farmers to reduce fertilizer applications and, thus, the achievement of agri‐environmental policy goals interacts with market price developments. In this study, we analyze how changes in price levels and volatility over time (i.e., 1991–2006 vs. 2007–2022) affected farmers’ preferences to reduce fertilizer application using statistical inferences of stochastic dominances. The analysis considers two cropping systems and fertilizer reduction measures: (i) grassland‐based milk production and the use of legumes and (ii) wheat production and the use of variable rate application. We show that the economic value of reducing fertilizer increased over time in both grassland‐based milk and wheat production. However, only in the case of wheat production was the reduction in fertilizer application observed as more risk‐reducing over time. In contrast, in grassland‐based milk production, the co‐movement of fertilizer and milk prices canceled out the increase in risk reduction. We conclude that changes in market price, along with agri‐environmental subsidies, can increasingly incentivize the reduction of fertilizer use.

Using slow-release fertilizers ensures the maintenance of litchi (Litchi chinensis Sonn.) production by enhancing soil nutrient supply and optimizing microbial communities

High temperatures and rainy climate conditions result in a very low nutrient utilization rate during crop cultivation in tropical regions. To determine whether slow-release fertilizers could have a positive impact on the yield and quality of litchi, and the soil ecology of orchards while reducing chemical fertilizer application, a field plot experiment with two fertilizer types (chemical fertilizers and lignin-based slow-release fertilizers) combined with a 0 %, 15 % and 30 % reduction of fertilizer application rates was set up from 2018 to 2019. Subsequently, a demonstration trial with an optimum dose of slow-release fertilizers with chemical fertilizers was carried out from 2019 to 2020 in acidic soils. The results demonstrated that all treatments could maintain the yield of litchi between 11,825–13,056 kg/hm2 in 2018–2019. Furthermore, compared to conventional chemical fertilizer treatment, the treatment of lignin-based slow-release fertilizer application with a 15 % fertilizer reduction significantly reduced the concentration of alkaline nitrogen by 19.9 % and available phosphorus by 22.0 % at the 20–40 cm soil layer during the maturity period of litchi growth. The result of the demonstration trial in 2019–2020 further confirmed that a slow-release fertilizer, along with a 25 % reduction in fertilizer application, could maintain high levels of soil alkaline nitrogen and available potassium at the 0–20 cm soil layer without affecting soil bulk density, total soil porosity, and soil aeration. Moreover, the treatment of lignin-based slow-release fertilizer application with a 15 % fertilizer reduction significantly increased the relative abundance of Proteobacteria (1.21 times) and decreased the abundance of Firmicutes (0.81 times) compared to conventional fertilization treatment at the 0–20 cm soil layer. In contrast, it decreased the relative abundance of Firmicutes (0.67 times) and Proteobacteria (0.37 times) at the 20–40 cm soil layer. Meanwhile, the fertilizer application only affected the soil fungi richness but did not increase their diversity. Applying slow-release fertilizers can realize the goal of reducing chemical fertilizers and ensuring excellent litchi production in tropical acidic soils.

Impact of Agricultural Division of Labor on Fertilizer Reduction Application: Evidence from Western China.

Nowadays, environmental friendly agriculture has become the world trend of modern agricultural development; fertilizer reduction application is an essential way to achieve sustainable development goals. With the deepening development of the agricultural specialized division of labor and socialized services, the division of labor economy can promote the economic input of fertilizer. Based on 540 survey data of farmers in the main rice-producing areas of Sichuan Province, this paper constructs a theoretical analytical framework for the impact of agricultural division of labor on fertilizer reduction application. A binary probit model was used to empirically analyze the effect of agricultural division of labor on fertilizer reduction application, and its mechanism was examined. The results show that: (1) both horizontal and vertical agricultural divisions of labor have positive and significant effects on the reduction in fertilizer application by rice farmers. All above results remain stable after treatment of endogeneity; (2) due to the migration of the rural labor, the horizontal division of labor is expressed as changes in the structure of labor and cultivation within the household which has changed. To achieve economies of scale, farmers increase specialization in production, resulting in reducing marginal cost and application of fertilizer; (3) the vertical division of labor is expressed in the adoption of external socialized services by farmers, which improves the land resource endowment of fragmentation and hydraulic conditions. Thus, it creates a good environment for fertilizer application to improve its application efficiency, which in turn promotes fertilizer reduction by farmers. Based on this, this paper proposes that the government should motivate farmers to deepen their participation in the horizontal and vertical division of labor. Meanwhile, it is also necessary to improve the agricultural specialization continuously and further promote the development of socialized services market.

Preharvest Reduction in Nutrient Solution Supply of Pepper (Capsicum annuum L.) Contributes to Improve Fruit Quality and Fertilizer Efficiency While Stabilising Yields

Optimising fertilisation is an important part of maximising vegetable yield and quality whilst minimising environmental hazards. An accurate and efficient scheme of irrigation and fertiliser based on plants’ nutrient requirements at different growth stages is essential for the effective intensive production of greenhouse pepper (Capsicum annuum L.). In this study, the effects of reducing fertilisation rate by 20%, 40%, 60% and 80% from the day 6 to day 0 before harvest for each layer of peppers on growth, yield, quality and nutrient utilisation were evaluated. The results showed that the morphological indicators (plant height and stem diameter) and biomass of plants decreased gradually with the increase in fertiliser reduction rate. Compared with control (CK) plants, the 20–40% reduction in fertiliser application rate did not cause a significant decrease in biomass and stem diameter but significantly increased the accumulation of N (13.52–15.73%), P (23.09% in 20% reducted-treatment) and K (13.22–14.21%) elements in plants. The 20–80% reduction in fertiliser application before harvest had no significant effects on the nutrient agronomic efficiency of N, P and K elements. However, it decreased the physiological nutrient efficiency and significantly improved the nutrient harvest index of N, P and K. Appropriate reduction in fertiliser application significantly increased the nutrient recovery efficiency (20–40% reduction) and nutrient partial-factor productivity (40% reduction) of N (3.35–6.00% and 12.87%), P (2.47–2.92% and 14.01%) and K (7.49–15.68% and 14.01%), respectively. Furthermore, reducing the fertilisation rate by 20–40% before each harvest had a certain positive effect on the C and N metabolism of pepper leaves and fruits. In particular, the activities of N metabolism-related enzymes (nitrate reductase, nitrite reductase, glutamine synthase, glutamate synthase and glutamate dehydrogenase) and C metabolism-related enzymes (sucrose phosphate synthase, sucrose synthetase, acid invertase and neutral invertase) in leaves and fruits did not significantly different or significantly increased compared with those in CK plants. The results of the representative aromatic substance contents in the fruit screened by the random forest model showed that compared with the CK plants, reducing the fertiliser application by 20–40% before harvest significantly increased the content of capsaicin and main flavour substances in the fruit on the basis of stable yield. In summary, in the process of pepper substrate cultivation, reducing the application of nutrients by 40% from the day 6 to day 0 before each harvest could result in stable yield and quality improvement of the pepper. These results have important implications for institutional precision fertilisation programs and the improvement of the agroecological environment.

Simulation Study on Nitrogen Pollution in Shallow Groundwater in Small Agricultural Watersheds in the Huixian Wetland

In this study, we investigated the influence of different simulations on the transport of shallow groundwater nitrogen in the Mudong River watershed of the Huixian Wetland, a karst wetland. Based on GMS (Groundwater Modeling System) software, the equivalent porous media model was used to simulate the transport of total nitrogen under different conditions in the study area. Two years of field monitoring data in the study area provided the input for the modeling. The SWAT (soil and water assessment tool) model was used to divide the study area into sub-basins. The initial concentration flux index W is first introduced in the equivalent porous medium model to calculate the initial concentration. The simulation results showed the difference between the simulated and monitored values of total nitrogen concentration was between 20% and 40% in 22.2% of the cases, and less than 20% in 66.7% of the cases, indicating that the solute transport model has good applicability in the Huixian Wetland. Parameter sensitivity analysis showed that fertilizer application was the main factor influencing total nitrogen. A 25% reduction in fertilizer application reduced total nitrogen emissions by 31.5% in sub-basin S3 and 22.5% in sub-basin S4. These reductions were greater than the abatement effect of changing land cover and managing river pollution. The pollution plume of total nitrogen was reduced by 38.5% in the southern part of sub-basin S3 (Mudong Lake) and by 40.2% in the western part of sub-basin S4 (Blacksmithing Village). The average concentration was reduced by 2.04 mg/L and 1.22 mg/L, respectively. This study shows that reasonable control of double-season rice nitrogen fertilizer application and appropriate land cover modification can help reduce total nitrogen emissions from wetlands in the Li River watershed and ensure the sustainable development of the local economy and groundwater.

Are Socialized Services of Agricultural Green Production Conducive to the Reduction in Fertilizer Input? Empirical Evidence from Rural China.

Reducing the use of chemical fertilizers in agricultural production is an inevitable requirement for achieving carbon neutrality and coping with global warming, and it is also an important measure for achieving green and sustainable agricultural development. Furthermore, the development of socialized services of green production provides a new approach to effectively reducing the use of fertilizers. Based on the survey data of 2202 rice growers in Jiangsu Province in 2021, this paper empirically analyzed the effects of socialized services of green production and social network on the reduction in fertilizer application by farmers. The results showed that both the socialized services of green production and social networks could significantly promote the reduction in fertilizer application by farmers. Social networks have a moderating effect between socialized services of green production and reduction in fertilizer application and can enhance the promotion of farmers' adoption of socialized services of green production to reduce the application of fertilizers. With consideration of the potential endogenous problems of the model and the robustness test by replacing the key explanatory variables and the explained variables, all of the results were stable. Therefore, it is emphasized that the government should cultivate the main body of agricultural socialized services, improve the socialized service system of green production, and promote the green development of agriculture by service scale operation. Equally, it is necessary to strengthen the construction of rural social networks for the exchange of fertilization experience and give full play to the positive role of social networks in the reduction in fertilizer application by farmers.

Comparisons between main and ratoon crops in resource use efficiencies, environmental impacts, and economic profits of rice ratooning system in central China

Rice production in China is constrained by excessive water consumption, labor shortage, large environmental footprint, and low economic profit. Rice ratooning is a promising practice to increase famers' profit with higher resource use efficiency and less environmental impact compared with other rice cropping systems. However, there is limited information on the differences in energy use efficiency, water and labor productivity, environmental footprint, and economic return between main crop (MC) and ratoon crop (RC) in this cropping system. This study was conducted to compare the system performance between the two crops of ratoon rice using on-farm survey data. Average grain yield was 8.40 and 4.55 t ha−1 for MC and RC, respectively. Although RC produced 45.9% lower grain yield, it had 57.3% less total energy input and 71.0% lower total production cost than MC, which resulted in a significantly higher energy use efficiency, net energy ratio, net economic return and benefit-to-cost ratio. Lower total energy input and production cost of RC was mainly attributed to the reduction in fertilizer application and labor input, respectively compared with MC. In addition, both labor and water productivity of RC was significantly higher than those of MC. Furthermore, the global warming potential (GWP) and yield-scaled GWP of RC was 59.3% and 23.4% lower than those of MC, respectively, due to lower agronomic inputs and GHGs emissions. Overall, our results suggested that RC had higher resource use efficiency, better economic performance, and less environment impact compared with MC.

Modeling fertilization impacts on nitrate leaching and groundwater contamination with HYDRUS-1D and MT3DMS

Agriculture is recognized as the major source of groundwater nitrate (NO3−) contamination; yet quantifying its effects is still challenging in large, due to the difficulty to track the transformation and fates of agricultural nitrogen (N) in soils and aquifers. In this study, a HYDRUS-1D model was adopted to explore water content and NO3− distribution in the unsaturated zone above groundwater table in an agricultural area. The resulting estimates of water flux and NO3− leaching through the unsaturated zone were used as input data in the application of the groundwater flow model Visual MODFLOW and mass transport model MT3DMS via a concentration recharge boundary. Nitrate leaching occurred mainly between May and September, accounting for 64% of the annual total. Four fertilizer application scenarios were developed, and their effects were compared in predictive simulations of groundwater NO3− concentrations using MT3DMS and quantitative analysis of NO3−-contaminated areas, the spatial and temporal distribution of groundwater NO3− concentration using ArcGIS. Predictions in the business as usual (scenario 1) showed that NO3− continued to accumulate in groundwater in the study area, with the maximum increased from 14 to 18 mg L−1 in 10 years. In the scenario 2 (2% increase in fertilizer application rate), peak groundwater NO3− was expected to exceed 20 mg L−1 in 2027. However, in both scenarios 3 (2% reduction in fertilizer application) and 4 (4% reduction in fertilization), the maximal NO3− concentrations were predicted to be lower than 12 mg L−1 in 2027. The integration of HYDRUS-1D, MT3DMS and GIS models offers a powerful tool for evaluating agricultural management impacts on aquifer water quality.

Source Apportionment of Nutrient Loads to a Mediterranean River and Potential Mitigation Measures

The aims of the study were to quantify nutrient loads from point and diffuse pollution sources in the Rio Mannu stream and to simulate mitigation measures for reducing nutrient loads delivered to the Santa Gilla wetland. The Soil and Water Assessment Tool model was used for simulating hydrology, nutrient balance and water quality. At the basin scale, the input from fertilisers was 80.3 kg ha−1 year−1 total nitrogen (TN) (87.6% of the total input) and 27.6 kg ha−1 year−1 of total phosphorus (TP) (99.8% of the total input). Atmospheric deposition and biological N-fixation together accounted for about 12% of the total TN input. The TN and TP from wastewater treatment plants (WWTPs) were about 14.2 t year−1 and 3.1 t year−1, respectively. Nutrient loads delivered to the river system differed among the sub-basins, with TP ranging from 0.2 kg ha−1 year−1 to 2.7 kg ha−1 year−1, and the sum of organic N and NO3-N ranging from 1.8 kg ha−1 year−1 to 22.9 kg ha−1 year−1. Under high flow conditions, NO3-N and TP accounted for 89% and 99% of the total load, respectively. The low flow contribution to the total load was very low, with NO3-N and TP accounting for 2.8% and 0.7%, respectively. However, the natural hydrological regime in the study area is intermittent, and low flow represents a critical condition for the water quality due to the high concentrations of TP and NO3-N from WWTP discharge. To improve the water quality, the reuse of treated wastewater from three WWTPs for irrigation purposes on olive cultivation, coupled with a 20% reduction in fertiliser application, was simulated. The results showed a reduction in nutrient loads at the outlet for all hydrological conditions. However, additional measures are needed for improving water quality.

A Race Against Time: Modeling Time Lags in Watershed Response

AbstractLand use change and agricultural intensification have increased food production but at the cost of polluting surface and groundwater. Best management practices implemented to improve water quality have met with limited success. Such lack of success is increasingly attributed to legacy nutrient stores in the subsurface that may act as sources after reduction of external inputs. However, current water‐quality models lack a framework to capture these legacy effects. Here we have modified the SWAT (Soil Water Assessment Tool) model to capture the effects of nitrogen (N) legacies on water quality under multiple land‐management scenarios. Our new SWAT‐LAG model includes (1) a modified carbon‐nitrogen cycling module to capture the dynamics of soil N accumulation, and (2) a groundwater travel time distribution module to capture a range of subsurface travel times. Using a 502‐km2 Iowa watershed as a case study, we found that between 1950 and 2016, 25% of the total watershed N surplus (N Deposition + Fertilizer + Manure + N Fixation − Crop N uptake) had accumulated within the root zone, 14% had accumulated in groundwater, while 27% was lost as riverine output, and 34% was denitrified. In future scenarios, a 100% reduction in fertilizer application led to a 79% reduction in stream N load, but the SWAT‐LAG results suggest that it would take 84 years to achieve this reduction, in contrast to the 2 years predicted in the original SWAT model. The framework proposed here constitutes a first step toward modifying a widely used modeling approach to assess the effects of legacy N on the time required to achieve water‐quality goals.

Tea yield maintained in PGPR inoculated field plants despite significant reduction in fertilizer application

A study was conducted to formulate dual plant growth promoting rhizobacteria (PGPR) inoculants, indigenous to each soil series where fields were located, to enhance growth and yield of tea (Camellia sinensis (L.) O. Kuntze), managed with low fertilizers inputs.Field experiments were conducted in five different locations with both early and later stages of mature tea fields representing three soil series i.e Kandy, Matale and Ukuwela. Soil series specific dual inoculants (i.e., Azospirillum sp. + Rhodococcus sp. for Kandy, Azospirillum sp. + Microbacterium sp. for Matale and Azospirillum sp. + Bacillus cereus for Ukuwela soil series) were tested in fields having respective soil series. In addition, a common consortium (Azospirillum sp. + Bacillus cereus) was tested across all the three soil series. They were tested along with a modified VP/UM 910 fertilizer mixture composed of 2/3 N and ½ P of the recommended application, and compared with three non-inoculated controls: an untreated control, a non-inoculated modified VP/UM 910 fertilizer control, and the VP/UM 910 recommended dose of fertilizer control, each with three replicates. Yield records were maintained and soils and leaf N and P contents were assessed after one year.The made tea yield of each soil series, with its soil series specific dual inoculants, conducted in four locations representing Kandy and Matale soil series, varied from 2521 to 2681 kg ha−1 yr−1 and remained comparable to fields with the recommended fertilizer treatment (2491–2697 kg ha−1 yr−1). Comparable yields to recommended fertilizer treatment due to series specific dual inoculant could also be observed in the location representing Ukuwela soil series.Results indicated that a 1/3 reduction of N and 1/2 reduction of P from the recommended fertilizer dosage VP/UM 910 are possible with application of dual PGPR inoculants formulated with soil series specific strains.

Aerial imagery or on-ground detection? An economic analysis for vineyard crops

Aerial and on-ground vegetation characterization technologies are continuously evolving. An experiment was conducted in a vineyard field in order to test the economic feasibility of applying fertilizers site specifically based on different mapping systems. The capacity of UAV missions and on-ground systems has been compared using depth cameras or LiDAR systems respectively in order to provide the necessary vineyard volume maps for specific applications like fertilization. Aerial imagery was obtained using a UAV equipped with a high-resolution RGB camera, and a digital surface model was reconstructed using photogrammetry procedures. On-ground crop reconstruction was performed using LiDAR-based measurements taken with an RTK-GNSS along the crop rows. Furthermore, a Kinect v2 sensor was also used as a low cost depth camera. All systems were tested in a commercial field, under sunlight conditions. Every technique provided a 3D dense point cloud from which volume was calculated. The results showed that volume values were always consistent and similar between the studied systems. The on-ground techniques provided the best details of the plants. However, the cost of acquisition was always higher than that of aerial imagery. Concerning the fertiliser application it should be noted that, the changes in shape and size of plants obtained within the vineyard indicate that continuous adjustment of the applied dose would be required to optimize the performed application. When using site-specific spraying based on the created maps, the dose was reduced by up to 80% of the total dosage used with a conventional application. A detailed analysis of savings indicates differences between the systems. The use of aerial imagery techniques resulted in positive net returns, whereas the on-ground technologies needed a faster time of acquisition in order of them to be profitable. Regarding efficacy, no significant differences between applications based on the constructed maps were found. This important reduction in fertilizer application could be followed by an equivalent reduction in plant protection products (e.g., fungicides). Thus, the use of some 3D characterization technologies has shown to be profitable at the current stage of development while also reducing the inputs and the environmental impact of agricultural tasks.

Modified control strategies for critical source area of nitrogen (CSAN) in a typical freeze-thaw watershed

The management of critical source areas of diffuse nitrogen (CSANs) remains challenging in freeze-thaw areas due to the different N loss characteristics in different hydrological conditions and seasons. To address these challenges, a modified strategy was proposed in this study using the Soil and Water Assessment Tool (SWAT) to simulate diffuse N loads in the study catchments. Specifically, the spatial and temporal variations of CSANs caused by differences in precipitation and seasons were considered. In addition, the selection of best management practices (BMPs) was selected according to BMP performance and their seasonal characteristics in diffuse N control. The diffuse N load formed during freeze-thaw seasons accounts for approximately 50% of the annual diffuse N load. The diffuse N load discharged to rivers was higher in wet conditions than dry conditions by 127.4% and 181.5% during freeze-thaw seasons and growing seasons, respectively. The spatial distribution of CSANs was more sensitive to differences between freeze-thaw and growing seasons. Among BMPs, buffer strips (BS), no tillage (NT) and reducing N fertilizer applications (RNFA) all showed differences in their diffuse N removal efficiency under different hydrological conditions and seasons, while reforestation operations were not affected by these factors. The benefit of reforestation operations was lower in flatter areas. When areas with slopes greater than 2 degrees were reforested, the average N removal efficiency of the 1st CSAN could be as high as 82.4%. In the 2nd CSAN, the average N removal efficiency of BS was relatively constant across freeze-thaw seasons. Across growing seasons, the N removal efficiency of BS in wet years was 8%-10% higher than in dry conditions due to the lower percentage of lateral flow. The average N removal efficiency of NT was higher during freeze-thaw seasons and lower during growing seasons with average values of 9.3% and 6.1%, respectively. The N control efficiency of RNFA 10% and RNFA 20% (a 10% or 20% reduction in fertilizer application, respectively) was highest during dry growing seasons with average N control efficiencies of 9.6% and 17.8%, respectively. This study is expected to improve diffuse pollution control in cold areas and to improve the understanding of how N removal efficiency of BMPs responds to variations in hydrological conditions.

Characteristics of Anthropogenic Soil Formed from Paddy near the River

Anthropogenic soil in cropland is formed in the process of subsoil reversal and the refill of soil into cropland. However, there was little information on the chemical properties within soil profiles in anthropogenic soil under rice paddy near the river. In this study, we investigated the chemical properties within soil profiles in the anthropogenic soil located at 4 sites in Gumi, Kimhae, Chungju, and Euiseong to compare with the natural paddy soil near the river. Among particle sizes, the sand content decreased under soil profiles but the silt and clay contents increased compared to the natural paddy soil in soil profiles. Organic matter content in topsoil of anthropogenic soil was lower than in that of natural soil, which was shown the contrary tendency within soil profiles. Also, the soil pH, available P2O5, and exchangeable cations were higher in anthropogenic soil compared to natural paddy soil at topsoil, which was maintained these tendency into soil depth. Nutrients may be equally distributed in anthropogenic soil during the process of refill in paddy soil near the river. This results indicated that anthropogenic soil would contribute to carbon sequestration, the mitigation of compaction, and reduction of fertilizer application in paddy soil. Therefore, characteristics of anthropogenic soil can be used for the soil management in cropland.

Innovative cropping systems to reduce N inputs and maintain wheat yields by inserting grain legumes and cover crops in southwestern France

The reduction in crop diversity and specialization of cereal-based cropping systems have led to high dependence on synthetic nitrogen (N) fertilizer in many areas of the globe. This has exacerbated environmental degradation due to the uncoupling of carbon (C) and N cycles in agroecosystems. In this experiment, we assessed impacts of introducing grain legumes and cover crops to innovative cropping systems to reduce N fertilizer application while maintaining wheat yields and grain quality. Six cropping systems resulting from the combination of three 3-year rotations with 0, 1 and 2 grain legumes (GL0, GL1 and GL2, respectively) with (CC) or without (BF, bare fallow) cover crops were compared during six cropping seasons. Durum wheat was included as a common high-value cash crop in all the cropping systems to evaluate the carryover effects of rotation. For each cropping system, the water use efficiency for producing C in aerial biomass and yield were quantified at the crop and rotation scales. Several diagnostic indicators were analyzed for durum wheat, such as (i) grain yield and 1000-grain weight; (ii) aboveground biomass, grain N content and grain protein concentration; (iii) water- and N-use efficiencies for yield; and (iv) N harvest index. Compared to the GL0-BF cropping system, which is most similar to that traditionally used in southwestern France, N fertilizer application decreased by 58%, 49%, 61% and 56% for the GL1-BF, GL1-CC, GL2-BF and GL2-CC cropping systems, respectively. However, the cropping systems without grain legumes (GL0-BF and GL0-CC) had the highest water use efficiency for producing C in aerial biomass and yield. The insertion of cover crops in the cropping systems did not change wheat grain yield, N uptake, or grain protein concentration compared to those of without cover crops, demonstrating a satisfactory adaptation of the entire cropping system to the use of cover crops. Winter pea as a preceding crop for durum wheat increased wheat grain production by 8% (383 kg ha−1) compared to that with sunflower − the traditional preceding crop − with a mean reduction in fertilizer application of 40–49 kg N ha−1 during the six-year experiment. No differences in protein concentration of wheat grain were observed among preceding crops. Our experiment demonstrates that under temperate submediterranean conditions, properly designed cropping systems that simultaneously insert grain legumes and cover crops reduce N requirements and show similar wheat yield and grain quality attributes as those that are cereal-based.

Dynamic adjustment in agricultural practices to economic incentives aiming to decrease fertilizer application

Input- and output-based economic policies designed to reduce water pollution from fertilizer runoff by adjusting management practices are theoretically justified and well-understood. Yet, in practice, adjustment in fertilizer application or land allocation may be sluggish. We provide practical guidance for policymakers regarding the relative magnitude and speed of adjustment of input- and output-based policies. Through a dynamic dual model of corn production that takes fertilizer as one of several production inputs, we measure the short- and long-term effects of policies that affect the relative prices of inputs and outputs through the short- and long-term price elasticities of fertilizer application, and also the total time required for different policies to affect fertilizer application through the adjustment rates of capital and land. These estimates allow us to compare input- and output-based policies based on their relative cost-effectiveness. Using data from Indiana and Illinois, we find that input-based policies are more cost-effective than their output-based counterparts in achieving a target reduction in fertilizer application. We show that input- and output-based policies yield adjustment in fertilizer application at the same speed, and that most of the adjustment takes place in the short-term.

Biochar forEucalyptusforestry plantations

Producing robust seedlings for forest plantation establishment is important as early growth influences potential yield and propagation is a significant budget component. The reputed benefits of biochar as a soil amendment may assist the growth and establishment of seedlings while simultaneously allowing for a reduction in fertiliser application. This study focussed on biochar's influence on the establishment of Eucalyptus nitens seedlings, changes to soil and plant chemistry and biomass accumulation. Eight doses of macadamia biochar (0-100 t ha -1 ) combined with two fertiliser rates were applied in a glasshouse pot trial and a 2-year field experiment. Soil Colwell potassium, sodium and nitrogen levels increased in response to biochar treatments while calcium, magnesium and manganese decreased. While soil nutrient dynamics varied under biochar treatments in both experiments, seedling growth did not reveal clear trends in response to biochar application.

Assessing the effectiveness of land and water management practices on nonpoint source nitrate levels in an alluvial stream–aquifer system

The search for ways to allay subsurface nitrate pollution and loading to streams over broad regional landscapes is taken up using a calibrated groundwater model supported by extensive field data. Major processes of transport and chemical reaction are considered in the irrigated vadose zone and the underlying alluvial aquifer in interaction with Colorado's Lower Arkansas River and its tributaries. Simulation of a variety of best management practices reveals that there is potential to lower regional nitrate concentrations in groundwater by up to about 40% and mass loading to the river network by up to 70% over a four-decade span. Over the 27BMP scenarios considered in this study, the most effective singular measures are reduction of fertilizer application and sealing of irrigation canals, while combinations of reduced fertilizer application, reduced irrigation application, canal sealing, and enhanced riparian buffer zones are predicted to have the greatest overall impact. Intermittent fallowing of 25% of the land to lease irrigation water also is found to be promising, resulting in a forecasted decrease of about 15% in nitrate groundwater loading to streams. Due to the strong similarity between the study region and other irrigated, fertilized alluvial river valley stream–aquifer systems worldwide, results of this study are expected to be broadly applicable.

Changes in Soil Physicochemical Properties Following Land Use Change from Paddy Fields to Greenhouse and Upland Fields in the Southeastern Basin of Dianchi Lake, Yunnan Province, China

Paddy fields in the southeastern basin of Dianchi Lake have rapidly changed to greenhouses since 1999. A total of 61 surface soil samples, including 43 greenhouse soils, 12 upland soils, and 6 paddy soils, were collected from a flat lowland area mainly used for agricultural production fields in the southeastern basin of Dianchi Lake. Analyses of the soil samples indicated that the greenhouse soils were characterized by a lower organic matter content, lower pH, and higher soluble nutrients than the paddy soils in the area. The lower organic matter content of the greenhouse soils was ascribed to environmental or management factors rather than the clay content of the soil. Accumulation of soluble nutrients, especially inorganic N, was due to over-application of fertilizers, which also caused soil acidification. The average amount of readily available N, P, and K accumulated in the greenhouse soils was estimated to be equal to or higher than the annual input of these nutrients as a fertilizer, indicating that a reduction in fertilizer application was possible and recommended. In contrast, a very low available Si content was observed in the paddy soils, suggesting the need for Si application for rice production.

Fertilizer, Irrigation, and Natural Ericaceous Root and Soil Inoculum (NERS): Effects on Container-grown Ericaceous Nursery Crop Biomass, Tissue Nutrient Concentration, and Leachate Nutrient Quality

We tested the effects of using an inoculum containing natural ericoid roots and soil (NERS) with two fertilizer and irrigation rates on plant growth, shoot (stems and leaves) nutrient concentration, leachate quality, and mycorrhizal colonization of container-grown Coast Leucothoe [Leucothoe axillaris (Lam.) D. Don] and Japanese Pieris [Pieris japonica (Thunb.) D. Don ex G. Don]. Uniform rooted liners were grown in 10.8-L containers in a pine bark, peatmoss, and sand (8:1:1 by volume) substrate medium in a randomized complete block design with four replications. A controlled-release fertilizer, Polyon® Plus 14-16-8 (14N–7P–6.6K), was incorporated in the substrate medium at the 100% manufacturer's recommended fertilizer rate [representing high fertilizer rate (HF)] (56 g per container) to supply 7.84 g nitrogen (N) and at 50% the manufacturer's recommended rate [representing low fertilizer rate (LF)]. Plants were irrigated using a cyclic drip irrigation system at high (HI) and low (LI) irrigation rates calibrated to supply 25.2 L of water and 16.8 L per week, respectively. On average, NERS inoculation increased shoot growth of Leucothoe and Pieris by 56% and 60%, respectively. Shoots of Leucothoe inoculated with NERS had higher N, phosphorus (P), magnesium (Mg), and manganese (Mn) concentrations than non-inoculated plants. At LF, nitrous-N (NOx-N) and orthophosphorus (PO4-P) concentrations in the leachate were reduced by 53% from Leucothoe and 62% from Pieris compared with HF-treated plants. A reduction of 37% and 36% in PO4-P concentration in leachates from Leucothoe and Pieris, respectively, were achieved at the reduced irrigation (LI) rate. The NERS inoculation reduced PO4-P concentrations in leachate from Leucothoe by 26% and NOx-N concentration by 33% in leachates from Pieris compared with non-inoculated plants. Compared with plants grown in the HI–HF treatment, the combination of LI–LF treatment reduced NOx-N concentrations in leachates from Leucothoe by 60% (P = 0.016) and reduced PO4-P leachate concentrations from Pieris by 72% (P = 0.0096). Decreasing the fertilizer rate to 50% of the recommended rate and the irrigation rate to 67% of the recommended rate in conjunction with the incorporation of NERS reduced leachate nutrient concentrations of two main water pollutants (NOx-N and PO4-P). Adopting the practice of adding NERS containing fungi and bacteria can be an effective system to increase shoot dry weight, allow reduction in fertilizer application, conserve water for irrigation, and minimize subsequent nutrient runoff in nursery operations.