Interaction among plant nutrients can yield antagonistic or synergistic outcomes that influence nutrient use efficiency. To provide insight on this phenomenon, peer-reviewed articles were selected that quantified the interaction effects of nutrients on crop yield levels. In total 94 articles were selected that described 117 interactions between all macro-and micronutrients for different agricultural crops. In 43 cases the interaction was synergistic, in 17 cases the interaction was antagonistic, and in 35 cases the interaction was zero-interaction; the other 23 cases were non-significant (16) or showed a negative response (7). Generally: (a) when the availability of two nutrients is characterized as deficient, a large increase in yield can be expected by diminishing these deficiencies: (b) for most macronutrients the mutual interactions on yield levels are synergistic; and (c) antagonistic effects on yield are often found for divalent cations. Knowledge of nutrient interactions can guide fertilizer design and optimization of fertilization strategies for high yields and high nutrient use efficiencies.

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. SWAP version 4; Theory description and user manual. Wageningen, Wageningen Environmental Research, Report 2780. 244 pp.; 57 fig.; 17 tab.; 312 ref. SWAP 4 simulates transport of water, solutes and heat in the vadose zone. It describes a domain from the top of canopy into the groundwater which may be in interaction with a surface water system. The program has been developed by Wageningen Environmental Research and Wageningen University, and is designed to simulate transport processes at field scale and during entire growing seasons. This is a new release with recent developments on atmosphere, soil water and crop growth interactions.This manual describes the theoretical background, model use, input requirements and output tables. • Acquisition, duplication and transmission of this publication is permitted with clear acknowledgement of the source.• Acquisition, duplication and transmission is not permitted for commercial purposes and/or monetary gain.• Acquisition, duplication and transmission is not permitted of any parts of this publication for which the copyrights clearly rest with other parties and/or are reserved.Wageningen Environmental Research assumes no liability for any losses resulting from the use of the research results or recommendations in this report. Wageningen Environmental Research Report 2780 | ISSN 1566-7197Photo cover: The picture on the front cover shows SWAP's core processes in the soil below a grass vegetation positioned in a rural area with different land uses. ContentsPreface 7 and hence the dynamics of light interception. During crop development a part of the living biomass dies due to senescence (Chapter 7).Grass growth is special: it is perennial, very sensitive to nitrogen, and grass is either grazed or mowed. Therefore SWAP includes a separate WOFOST module for grass, which simulates these special grass features (Chapter 7).SWAP simulates transport of salts, pesticides and other solutes that can be described with basic physical relations: convection, diffusion, dispersion, root uptake, Freundlich adsorption and first order decomposition. In case of advanced pesticide transport, including volatilization and kinetic adsorption, SWAP can be used in combination with PEARL. In case of advanced transport of nitrogen and phosphorus, SWAP can be used in combination with ANIMO or Soil-N (Chapter 8).SWAP may simulate soil temperature analytically, using an input sine function at the soil surface and the soil thermal diffusivity. In the numerical approach, SWAP takes into account the influence of soil moisture on soil heat capacity and soil thermal conductivity. The top boundary condition may include air temperatures or soil surface temperatures (Chapter 9).The snow module calculates the accumulation and melting of a snowpack when the air temperature is below a threshold value. The water balance of the snow pack includes storage, incoming snow and rain and outgoing melting and sublimation. Melting may occur due to air temperature rise or heat release from rainfall. When a snowpack is p...

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