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  • Crop Residue Management for Lowland Rice-Based Cropping Systems in Asia. Bijay-Singh, Y.H. Shan, S.E. Johnson-Beebout, Yadvinder-Singh, and R.J. Buresh. 2008. Advances in Agronomy, 98, pp 117-199. ISSN 0065-2113, DOI: 10.1016/S0065-2113(08)00203-4.
  • Nitrogen uptake, fixation and response to fertilizer N in soybeans: A review.Salvagiotti, F., K.G. Cassman, J.E. Specht, D.T. Walters, A. Weiss, and A. Dobermann. 2008. Field Crops Research, 108, pp 1-13.
  • Organic agriculture cannot feed the world. Connor, D.J. 2008. Field Crops Research, 106, pp 187-190.
  • Sugarcane for Bioethanol: Soil and Environmental Issues. Hartemink, A.E. 2008. Advances in Agronomy, 99, pp 125-182. ISSN 0065-2113, DOI: 10.1016/S0065-2113(08)00403-3.
  • Crop research a target of international investment. Nature, 456, 14 (2008). DOI: 10.1038/456014e. www.nature.com.

Perspectives for Plant Production in Switzerland in 2050

Basic conditions for plant production in Switzerland will be substantially different by 2050, mainly by increased competition in global and free markets, climate change causing more frequent disasters, and by scarcity of resources: soil quality will diminish, arable land will disappear and water will no longer be constantly available. Is plant production in Switzerland still feasible and expedient under these circumstances? What are the requirements for plant production in the future? Experts in plant sciences addressed these questions during the project "Perspectives for Plant Production 2050" of the Swiss Society of Agronomy (SSA). The conclusions of the study showed that the sufficient production of high quality food is only possible based on scientific and technological progress in plant sciences and production. In addition, conservation of fertile agricultural land and public commodities such as recreational landscapes, secure supply of drinking water and conservation of biodiversity are a necessity. The SSA highlights the requirements for research and development for enabling plant production of high quality and quantity in the future.

Effect of N and K Fertilizers on Yield and Quality of Greenhouse Vegetable Crops

The application of large amounts of fertilizers, a conventional practice in northern China for the production of vegetable crops, generally leads to substantial accumulation of soil nutrients within a relatively short period of time. A fixed field experiment was designed to study the effects of nitrogen (N) and potassium (K) fertilizers applied to optimize the yield and quality of typical vegetable crops. Application of N and K fertilizers significantly increased the yields of kidney bean. The largest yields were obtained in the first and second years after application of 1,500 kg N and 200 kg K2O/ha. In the third year, however, there was a general decline in yields. Maximum yields occurred when intermediate rates of N and K (750 kg N and 300 kg K2O/ha) were applied. However, no significant differences were observed in the concentrations of vitamin C (VC) in kidney bean among different years and various rates of fertilizer treatments. Yields of tomato grown in rotation after kidney bean showed significant responses to the application of N and K in the first year. In the second year, the yields of tomato were much lower. This suggested that the application of N fertilizer did not have any effect upon tomato yield, whereas application of K fertilizer did increase the yield. Application of K fertilizer was often associated with increased sugar concentrations.

Variability of Soil Properties, Early Phosphorus and Potassium Uptake, and Incidence of Pests and Weeds in Relation to Soybean Grain Yield

Successful crop management requires understanding relationships between site characteristics and crop yield. We studied intercorrelations among soil and crop properties using factor analysis (FA) and principal components analysis (PCA), and their relationships with soybean [Glycine max (L.) Merr.] within-field yield variability. Site variables (22) measured on 0.2-ha cells of 12- to 20-ha areas of five Iowa fields were: elevation; soil texture; extractable nutrients; incidence of soybean cyst nematode (Heterodera glycines) (SCN), diseases, and weeds; soybean dry weight (DW), height, and P and K uptake at V5; plant height at R5; and grain yield. Agronomic interpretations of interrelationships among site variables were more straightforward for FA than for PCA. The factors conditions for early growth and nutrient uptake and intrinsic soil properties were present in all fields, plant P and K availability was present in three fields, and the factor soybean pests, weeds or plant growth was present in the other fields. Factor analysis and PCA accounted for 62 to 64% of the yield variability in the field with the largest yield CV (30%) and 5 to 35% in the other fields (CV 2.8 to 5.9%). Two factors related significantly to yield in two fields (plant P and K availability and intrinsic soil properties) while others were specific to one field. Factor analysis identified groups of interrelated site variables, showed how they accounted for yield variability, and showed that single measurements seldom account for most yield variation in a field.

Effect of Potassium and C/N Ratios on Conversion of NH+4 in Soils

Two soils, one consisting of 1:1 clay minerals at pH 4.5 and the other containing 2:1 clay minerals at pH 7.0, were used to estimate the conversion of added NH+4 under different C/N ratios (glucose as the C source) and the addition of potassium. Under lower C/N ratios (0:1 and 5:1), a large part of the added NH+4 in the acid soil was held in the forms of either exchangeable or water soluble NH+4 for a relatively long time and under higher C/N ratio (50:1), a large amount of the added NH+4 was directly immobilized by microorganisms. In the second soil containing appreciable 2:1 type clay minerals a large part of the added NH+4 at first quickly entered the interlayer of the minerals under both lower and higher C/N ratios. In second condition, however, owing to microbial assimilation stimulated by glucose the newly fixed NH+4 could be completely released in further incubation because of a large concentration gradient between external NH+4 and fixed NH+4 in the mineral interlayer caused by heterotrophic microorganisms, which imply the fixed NH+4 to be available to plants. The results also showed that if a large amount of K+ with carbon source together was added to soil, the higher K+ concentration of soil solution could impede the release of fixed NH+4, even if there was a lot of carbon source.

Combining Organic and Mineral Fertilizers for Integrated Soil Fertility Management in Smallholder Farming Systems of Kenya: Explorations Using the Crop-Soil Model FIELD

Integrated soil fertility management (ISFM) technologies for African smallholders should consider (i) within-farm soil heterogeneity; (ii) long-term dynamics and variability; (iii) manure quality and availability; (iv) access to fertilizers; and (v) competing uses for crop residues. We used the model FIELD (Field-scale resource Interactions, use Efficiencies and Long term soil fertility Development) to explore allocation strategies of manure and fertilizers. Maize response to N fertilizer from 0 to 180 kg N ha-1 (±30 kg P ha-1) distinguished poorly responsive fertile (e.g., grain yields of 4.1-5.3 t ha-1 without P and of 7.5-7.5 t ha-1 with P) from responsive (1.0-4.3 t ha-1 and 2.2-6.6 t ha-1) and poorly responsive infertile fields (0.2-1.0 t ha-1 and 0.5-3.1 t ha-1). Soils receiving manure plus fertilizers for 12 yr retained 1.1 to 1.5 t C ha-1 yr-1 when 70% of the crop residue was left in the field, and 0.4 to 0.7 t C ha-1 yr-1 with 10% left. Degraded fields were not rehabilitated with manures of local quality (e.g., 23-35% C, 0.5-1.2% N, 0.1-0.3% P) applied at realistic rates (3.6 t dm ha-1 yr-1) for 12 yr without fertilizers. Mineral fertilizers are necessary to kick-start soil rehabilitation through hysteretic restoration of biomass productivity and C inputs to the soil.

Potassium Fertility and Terrain Attributes in a Fragiudalf Drainage Catena

Site-specific management of soil fertility has been based on soil sampling in grid patterns or within soil mapping units without taking full advantage of terrain

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December 2008

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