No abstract

No abstract

No abstract

Assessing the sustainability of complex development processes requires multi-causal and integrated analyses. We develop a system-based methodology, rooted Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.in interdisciplinary discussion and consensus building between 15 experts, to construct a multi-causal diagram which examines the sustainability of the Argentine Pampaś process of agriculturization. The resulting diagram includes 25 factors and provides a big-picture of the multiple dimensions and interrelations affecting sustainability. According to this examination, the increasing concentration of production and the incorporation of technological innovations, triggered by economic and institutional factors, are the cause of environmental distresses and social changes, whose consequences for sustainability are still highly disputed. Nevertheless, the symptoms of both environmental and social unsustainability are more evident in the case of the extraPampean regions than in the Pampas. This suggests that the Pampean agriculture model should not be transferred to these regions without substantial modifications. The experts did not reach consensus on whether the agriculturization process is overall sustainable or unsustainable. Lack of consensus revolved mainly around opposing perspectives regarding the significance of the threats to environmental sustainability. The magnitude of socio-distributive unbalance and loss of rural jobs were also contentious. Yet, the paper shows how the exercise of building a joint causal diagram was undoubtedly helpful for linking piece-meal disciplinary facts, brought in from all fronts, into a comprehensive and coherent picture.

The development of structure in soils is also important for controlling wind and/or water erosion processes (Lal The development of well-structured soils is a goal for achieving and Elliott, 1994;Skidmore et al., 1994). For example, sustainable and productive agricultural systems. Nevertheless, the maintenance of soil structure in continuous no-till (NT) soils has the presence of large stable soil fragments in seedbeds sometimes been thought to induce soil conditions that are detrimental promotes the occurrence of surface roughness, reducing to crop yields. The objectives of this research were to characterize soil erodibility by wind (Chepil, 1953) as well as water the effects of periodic tillage disruption in otherwise NT systems on erosion (Deizman et al., 1987). Well-structured soils soil properties and the yields of winter wheat (Triticum aestivum L.), have higher infiltration rates and can maintain their pore double-cropped soybean [Glycine max (L.) Merr.], and maize (Zea M. Díaz-Zorita,

Crop productivity under dryland conditions is largely limited by soil water availability. Soil organic matter (SOM) contents have been found to be a reliable index of crop productivity in semiarid regions because it positively affects soil water‐holding capacity. Our objectives were to explain differences in wheat (Triticum aestivum L.) yields in response to SOM levels and related properties and to quantify the contribution of a unit increment of SOM content to soil productivity during 1991, 1992, and 1994 on a total of 134 production fields in the semiarid Argentine Pampas. Wheat yields were related to both soil water retention and total organic C (TOC) contents in the top layers (0–20 cm) in years with low moisture availability (1992 [r = 0.51, P < 0.01] and 1994 [r = 0.59, P < 0.01]), and were related to both total N and available P contents in a year without water deficit stress (1991 [r = 0.58, P < 0.01]). Wheat yields over all years were linearly related to TOC (r = 0.68, P < 0.01) when these contents were <17.5 g kg−. Dependence of wheat yields on soil water retention and on TOC contents under water deficit was related to the positive effect of these soil components on plant‐available water. In the absence of water deficit (1991), nutrient availability was the limiting factor. Losses of 1 Mg SOM ha− were associated with a decrease in wheat yield of approximately 40 kg ha−. These results demonstrate the importance of using cultural practices that minimize losses of soil organic C in the semiarid Argentine Pampas.

Although the relevance of biological N nutrition of soybean [Glycine max (L.) Merr.] is recognized worldwide, inoculation with Bradyrhizobium japonicum shows variable results and the benefi t needs to be validated under current crop production practices. We conducted statistical analysis of soybean fi eld trial data to provide insight into factors aff ecting the effi cacy of soybean inoculation under contrasting crop production conditions. Most experimental sites, 187 trials in the United States and 152 trials in Argentina, were in soils with soybean history and naturalized B. japonicum strains. Yield increases were greater in Argentina (190 kg ha -1 equivalent to 6.39%) than in the United States (60 kg ha -1 equivalent to 1.67%). Tillage methods did not aff ect inoculant performance. In the United States, inoculation was more eff ective in soils with higher pH (>6.8) while in Argentina the greatest inoculation eff ect on crop production occurred in soils with a lower pH (<5.5). In the United States, where most of the trials were in rotation with corn (Zea mays L), the greatest positive eff ect of inoculation was observed in late planted soybean crops and independent of soil organic matter (SOM). In Argentina, the inoculant had its greatest eff ect in soils with no soybean history, a relatively high SOM, higher levels of soil extractable P and S, and in areas with greater precipitation during early reproductive growing stages. In both regions, the yield increases due to B. japonicum inoculation support the regular use of this practice to help provide adequate conditions for soybean production.M. Leggett, Novozymes BioAg, Research and Development, 3935 Th atcher Ave.,

Nitrogen availability and drought influence wheat (Triticum aestivum L.) grain yields in the semiarid and subhumid Pampas region of Argentina. The application of fertilizers containing osmoprotectants, such as glycinebetaine, to crop canopies might reduce crop losses caused by environmental stresses. The objectives of this study were (a) to determine the effects on wheat grain yields of the foliar application of a commercial fertilizer with glycinebetaine, and (b) to establish, under farmers’ field conditions, the relation between soil properties and the productivity of wheat crops treated with the same product. Two experiments were conducted in the north‐western part of the Buenos Aires province of Argentina on Typic Hapludolls and Entic Hapludolls. In the first, the treatments were N fertilization (0, 23 and 46 kg ha−1) and the foliar application to the wheat crop, in the vegetative stages, of a foliar fertilizer containing N, P, Zn and glycinebetaine (0 and 2.5 l ha−1). The second experiment was carried out on 10 farmers’ fields, for each of which the treatment was the foliar application to the wheat crop, in the vegetative stages, of the same foliar fertilizer (0 and 2.5 l ha−1). In both experiments, the grain yield, the individual grain weight, the number of grains per spike and the spike and plant density at the physiological maturity of the crops were determined. Soil organic matter (SOM) and available P were determined in each of the 10 fields of the second experiment. Wheat grain yields were increased by N fertilization and glycinebetaine treatment. The number of grains per spike was higher in the treatments with glycinebetaine application. In the farmers’ fields, the grain yields of the treatments with the application of the product with glycinebetaine were, on average, 18 % higher than those of the non‐treated plots, with greater responses at sites with low SOM levels. We conclude that, in subhumid regions with a dry period between the tillering and flowering stages of wheat, the foliar application of foliar fertilizers containing glycinebetaine at the vegetative stages of crop development enhances grain yields by increasing the number of grains per spike. This response is independent of the SOM level or the N fertilization rate.