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Although a significant fraction of the global soil–atmosphere exchange of greenhouse gases (GHGs) occurs in semi-arid zones little is known about the magnitude of fluxes in grazed steppe ecosystems and the interference with grazing intensity. In order to assess GHG burdens and to identify options of climate-optimized livestock farming, GHG emissions of sheep grazing in Inner Mongolia steppe were analyzed. Carbon sequestration and field-fluxes of methane (CH4) and nitrous oxide (N2O) were measured at a range of steppe sites differing in grazing intensity and management, i.e. ungrazed (UG), ungrazed with hay cutting (HC), lightly grazed (LG), moderately grazed (MG), and heavily grazed (HG). In addition, GHG emissions from enteric fermentation, manure management, and farming inputs (i.e. fossil fuels) were quantified for LG, MG, and HG. Monte Carlo simulation was used to estimate uncertainty. Sheep grazing changed the net GHG balance of the steppe from a significant sink at UG (−1476 ± 2481 kg CO2eq ha−1 year−1) to a significant source at MG (2350 ± 1723 kg CO2eq ha−1 year−1) and HG (3115 ± 2327 kg CO2eq ha−1 year−1). In a similar way, the GHG intensity increased from 8.6 ± 79.2 kg CO2eq kg−1 liveweight gain at LG up to 62.2 ± 45.8 and 62.6 ± 46.7 kg CO2eq kg−1 liveweight gain at MG and HG, respectively. GHG balances were predominantly determined by CO2 from changes in topsoil organic carbon. In grazing systems, CH4 from enteric fermentation was the second most important component. The results suggest that sheep grazing under the current management changes this steppe ecosystem from a sink to a source of GHGs and that grazing exclusion holds large potential to restore soil organic carbon stocks and thus to sequester atmospheric CO2. The balance between grazing intensity and grazing exclusion predominantly determines GHG balances of grass-based sheep farming in this region. Therefore, a high proportion of ungrazed land is most important for reducing GHG balances of sheep farms. This can be either achieved by high grazing intensity on the remaining grazed land or by confined hay feeding of sheep.

The effect of seed coatings or drilled granules containing phosphorus (P) on the early growth of wheat was evaluated in a pot trial in two soils differing in P-sorption capacity. P as monocalcium phosphate (MCP) was applied in seed coatings (C) at rates of 0 (inert coating of diatomaceous earth), 5 and 10 kg P ha−1 whereas drilled rates (D) of P were applied at 0, 5, 10, 20 and 40 kg P ha−1 to wheat sown at the equivalent of 60 kg ha−1. The soils used were an aquic haplustalf with low (LS) and a gibbsiorthox with high (HS) P-sorption capacities respectively. Both soils were deficient in P, having 7.3 and 13.1 ppm available P in the LS and HS soils respectively. Emergence was recorded and plant height was measured at regular intervals. Shoot and root dry weights and P contents were determined in the final harvest at 27 days after sowing. Emergence was significantly delayed only by C10. Cumulative plant height per pot of C5 was significantly greater than that of C0, C10, D0, D5 or D10 from day 17 onwards. The only drilled treatments to produce a significant increase in plant height over D0 were D20 and D40. Dry weights increased in the LS soil up to 20 kg P ha−1 and up to 40 kg P ha−1 in the HS soil. Whilst C10 suffered some injury during emergence which also reduced the early growth of that treatment, seed coating at 5 kg P ha−1 resulted in more effective use of P than an equivalent drilled rate in both soil types, particularly with respect to plant height and root weight.

Process-based models are useful tools for estimating the complex interactions between plant, soil and climate systems, assessments which are necessary for improving nutrient cycling and reducing trace gas emissions. Incorporation of knowledge gained through new research is ongoing, thus there is a need for evaluation of model processes and process interactions. In this study, three sites in eastern Canada (St. Bruno, St. Jean, and Ottawa) planted with spring wheat during the years 1993–2007 were used to evaluate and compare the water and N process simulations of the models DayCent, DNDC, and STICS. The simulated soil moisture by all models was generally well represented with low ARE (< 8%) and an EF > 0.1. The unsaturated flow mechanism included in DayCent further improved soil moisture estimates compared to the other models. When sufficient replicate data was available measurement variability was considered, resulting in soil nitrogen being only slightly underestimated (ARE of −10, −1, and −22%, for DayCent, DNDC, and STICS, respectively). On average across the three sites, considering all statistics, the DNDC model proved to be most accurate for simulating mineral N, followed by DayCent and then STICS. Continued process model development is reliant on measurement datasets that can accurately represent carbon and nitrogen dynamics. Frequently, site specific biases convolute model mechanism evaluation and thus assessments have to be conducted across numerous sites to better benchmark model performance. On this premise a comprehensive multi-site inter-model mechanism evaluation was conducted and future model development needs were identified.

The effects were examined of applying 114g of two fertilizer mixtures containing N, P, K and Mg in weight ratios of 1:1:1:2 and 1:1:1:1 on growth and mineral composition of oil-palm seedlings grown in polythene bags filled with two different soil types. The potting soils were taken from the top layers of the Orlu and Calabar series, which belong to the order of the Ultisols, and which are the main oil-palm supporting soils in Nigeria. Significant differences did not occur between equal split application of the fertilizer mixture twice at 2 and 8 months, thrice at 2, 5 and 8 months and seven times at 2, 3, 4, 5, 6, 7 and 8 months for oil-palm seedling growth and the percentage N, P, K, Mg and Ca of the leaf, stem and root fractions. Significant differences did not also occur between the two fertilizer mixtures for these parameters. A 1:1:1:1 N, P, K and Mg fertilizer mixture instead of the present 1:1:1:2 ratio in use, applied at 2 and 8 months after sowing, is recommended for both types of oil-palm supporting soils in Nigeria.

When semidwarf, fertilizer-responsive varieties became available in the late 1960s, a range of policy and institutional changes were also introduced to exploit the potential of these varieties. As a result, adoption of both high-yielding varieties and chemical fertilizers increased rapidly, especially in irrigated areas. A review of how these policy and institutional changes have influenced adoption of chemical fertilizers is presented using a microeconomic model of technology adoption. It is argued that fine-tuning of these policy and institutional innovations will continue to be important in further increasing rice yields and farmers' incomes, especially in rainfed areas where fertilizer use is still very low. In the more intensive irrigated areas, where chemical fertilizer use is already high, a change in the paradigm from that of encouraging higher input use to achieving increased input-use efficiency is suggested. Based on a conceptual model of the likely evolution of the nature of rice production systems in Asia, a somewhat targeted approach to the design of technological, policy, and institutional interventions for improving farmers' nutrient management practices is recommended.

Contamination of groundwater from point and non-point sources is one of the major pollution problems. The agricultural community has become keenly aware of the impact of irrigation and fertilization on groundwater quality. In the plains of Austria groundwater is used as a major source of drinking water. In the last few decades nitrate concentrations in groundwater have increased dramatically. Among the various land uses, agriculture is reported to be the main source of groundwater contamination by nitrate. The study presented here was carried out at Tullnerfeld where nitrate levels in groundwater have been reported to be as high as 100 mg l−1. To assess the contribution of various land uses to nitrate in groundwater, the Institute for Hydraulics and Rural Water-Management has installed facilities for measuring nitrate leaching and percolation under different cropping and management systems. The nitrate from fertilizers was measured using six lysimeters once a week. At the same time the nitrate levels in groundwater were simulated using the physically based model Environmental Policy Integrated Climate (EPIC). This paper gives a brief account of groundwater nitrate in Austria. The case study presented in this paper deals with the qualitative and quantitative aspects of groundwater nitrate by fertilizers and cover crops.

Nitrification rates (n) in the floodwater of an alkaline clay were measured in the absence or presence of rice plants by inhibition of ammonium oxidation and 15N-dilution techniques. Floodwater nitrate concentrations in control treatments showed a marked diurnal variation, and were higher than in the inhibitor treatments after the first day. Ammonium concentrations in floodwater declined exponentially in all treatments, being markedly affected by diffusion and NH3 volatilization but little affected by nitrification and plant uptake. Nitrification rates in floodwater estimated by 15N-dilution were generally higher than the rates estimated by the inhibitor method. Estimates of n were generally higher during daylight hours than at night, and did not differ significantly between planted and unplanted pots. Microbial immobilisation of labelled ammonium and gross N immobilisation were not affected by addition of the nitrification inhibitor 2-ethynylpyridine.

Swine production represents more than 25% of net agricultural incomes in some Spanish regions. Most of the 25 million t of swine slurry produced yearly in Spain is applied to agricultural fields by surface broadcasting (splash-plate) with important atmospheric N losses that reduce the fertilizer value of the slurry. Surface banding, incorporation, and injection into the soil are recommended methods to reduce N losses. We examined during two consecutive years the response of a wheat crop to swine slurry (SS) applied in the first year at two rates (30 and 60 Mg ha−1) using two application methods: splash-plate (SP) and soil incorporation (SI). After SS application, the soil was sampled intensively to establish the actual amount of SS in the soil (N recovery) and its spatial variability (distribution uniformity) in the two methods. Wheat yield, above ground dry matter and N uptake were measured along the 2 years. Swine slurry distribution uniformity and soil N-recovery were higher in SI than in SP, but grain yield and N uptake were independent of the application method in the 2 years. Reliable management practices compatible with the protection of the environment require further studies on the pathways and the availability of N to crops subject to SS incorporation in the soil at the moment of application.

Organic farming systems are often nutrient-limited. Moreover, even if organic guidelines emphasize the reliance on ecological processes and recycling, the trend towards farm specialisation induces an increased reliance on off-farm fertilising materials in arable areas. There is, therefore, a need to better understand the drivers of nutrient inflows on organic farms. Our objectives were to assess the nitrogen (N,) phosphorus (P) and potassium (K) farm-gate inflows through fertilising materials, and the nutrient budget and use efficiency over a large range of organic farming systems. To do this, 56 interviews with organic farmers concerning their nutrient management for the years 2010 and 2011 were carried out in 2012 in three French agricultural districts distributed over a gradient of farming activity. The results showed that the farm-gate fertilising material inflows were strongly related to both the ratio of land under cereal and oilseed crops (proxy of nutrient ‘demand’) and the stocking rate (proxy of nutrient ‘supply’). However, other inflows (biological N fixation, feed use, fodders and straws) increased with the stocking rate, leading to low farm-gate N and K use efficiency (0.2 and 0.7, respectively) on livestock farms compared to arable, stockless farms (1.4 and 3.5, respectively). Such results helped to disentangle the drivers of nutrient use in organic farms compared to previous analyses based solely on farm production typology.