Natural soils change by long-term pedogenetic mechanisms, but tillage effects can also strongly affect the evolution of soils, mainly their physicochemical properties. The present paper describes the impact of fertilizers and amendments on soil mineralogy in experimental plots, without plant interaction.

The soils of the 42 plots experiment at the INRA experimental station in Versailles (France) have been managed with fertilizers without plant growth since 1929. Strong changes in pH were observed and cation exchange capacities doubled between low and high pH (from 3.6 to 8.2). Strong acidification caused more evolution in the clay particle distribution without selective action on the clay composition.

While the clay content varied only slightly, the organic matter content changed considerably, decreasing with non-organic treatment and increasing in the plot with manure treatment. The major clay minerals in the experimental plots are two disordered illite-smectite mixed-layer minerals, with minor amounts of illite/mica and kaolinite. Most treatments effected only minor changes in clay mineralogy. However the illite (non-expandable mineral) content increased in plots with K addition either as KCl treatment or in manure amendments by increasing the illite content and the illite (non-expandable layer) content of the I-S minerals. Manure changed the I-S mineral to a greater extent.

Macronutrient inputs to annual cropping systems can benefit weeds as well as crops, sometimes decreasing or eliminating the benefits of fertilization. This interaction between fertility management and integrated weed management is becoming increasingly important as these fields increase their focus on efficiency and prevention, respectively. The risk of increased weed competition reflects the fact that weed biomass and height may be highly responsive to nitrogen, phosphorus, and/or potassium. This generalization is supported by monoculture studies of species such as redroot pigweed (Amaranthus retroflexus L.), common lambsquarters (Chenopodium album L.), and barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] and by ecological theory. However, field studies indicate variation in the effects of macronutrients on weed–crop competition and crop yield, even within species groups. To address challenges in interpreting, comparing, and extrapolating from these diverse reports, we propose a conceptual framework that summarizes the mechanisms underlying observed variation within and between studies. This framework highlights functional traits and trends that help predict yield outcomes in binary weed–crop interactions. Important factors include timing of emergence, maximum heights of the weed and crop, and relative responsiveness to the added nutrient. We also survey recent work on the effects of nutrient source (e.g., the composition of organic amendments) on weed–crop competition. Because different sources vary in their nutrient release dynamics and supplied nutrient ratios, they may have dramatically different effects on weed–crop competition and crop yield. Finally, we offer a guide to best practices for studies of fertility effects on weed–crop competition. Although this review highlights several topics requiring further research, including fertility effects on multispecies interactions and interactions with other environmental factors, emerging methods offer considerable promise. Ultimately, an improved understanding of nutrient effects on weed–crop competition will contribute to the efficient and effective management of diverse cropping systems.

Weeds are often more competitive with crops at higher soil nutrient levels. This can result in increased dependency on herbicides and tillage to maintain adequate weed control. A number of studies have shown weeds accumulate higher concentrations of nitrogen, phosphorus, potassium, calcium, and magnesium than crops, thus depleting soil nutrient levels more quickly and reducing crop yield. Understanding basic mechanisms and timing of nutrient uptake in weeds and crops can lead to fertilization strategies which will enhance the competitive ability of crops while reducing interference from weeds. Such strategies can include deep band application of fertilizers to the crop row, as opposed to broadcast applications. Banding techniques also reduce the potential for nitrate contamination of surface or groundwater. The addition of nitrification inhibitors or increasing the proportion of nitrogen as ammonium or urea in fertilizer mixtures can restrict growth of ammonium- or urea-sensitive weeds. The timing of fertilizer applications can take advantage of maximal rates of nutrient uptake into crop roots at specific developmental stages. In addition, nutrient use efficiency can be enhanced by choosing appropriate crop cultivars, maintaining effective weed control practices, or altering row spacing or seeding rate to increase accumulation of nitrogen, phosphorus, and potassium in crops.

Effects of ammonium and methylammonium on foliar uptake of 14C-thifensulfuron, in the presence of 0.2% nonionic surfactant by vol, into velvetleaf were investigated. Total 14C uptake into velvetleaf 24 h after treatment was only 15% without addition of nitrogen, but addition of 0.32 M NH4Cl, urea ammonium nitrate, or CH3NH2·HCl increased total 14C uptake to 31, 38, or 59%, respectively. Total 14C uptake 24 h after treatment was increased 3- and 4-fold by addition of 0.08 and 0.16 M CH3NH2·HCl, respectively, but was not increased further by greater CH3NH2·HCl concentrations. Although the increase in 14C uptake was followed by an increase in total 14C translocated, the relative amount of 14C translocated (expressed as a percentage of total 14C uptake) was not affected by nitrogen additives. Enhancement of uptake of 14C-thifensulfuron by CH3NH2·HCl was partially reversed by addition of 0.16 M CaCl2 to the application solution.

This article examines the determinants of chemical consumption by French winegrowers on an individual basis. We introduce criteria relating to the structure of vineyards and the financial situation of the winegrowers. Using data from the Farm Accountancy Data Network (FADN-RICA) for the period 2002–2007 from an annual sample of 607 winegrowers, we study the different factors that encourage winegrowers to use chemical inputs to protect or increase the yield of their vines. Drawing on transversal and longitudinal analyses, we illustrate the benefits derived from differentiating the demand for inputs according to their classification: pesticides or fertilizers. Climatic variables, physical size, and turnover all act as driving forces in the decision to use chemical inputs. We show that taking out crop insurance functions as a substitute for inputs and observe a double moral hazard effect: Winegrowers who increase their insurance coverage reduce their consumption of inputs the most and receive greater compensation; among insured winegrowers, those who use the most inputs make the most claims. As wine grape growing is a consistent activity conducted over a long period, we observe permanence in patterns of use of chemical inputs. (JEL Classifications: Q12, Q13, Q14)

Plots in the Jamaican montane forest were fertilized with nitrogen or with phosphorus to test the hypothesis that growth of trees in this natural forest is limited by the supply of N and P from the soil.

Once a year from 1983 to 1986, urea was added to one plot (at 150 kg N ha−1 y−1) and triple superphosphate was added to another (at 50 kg P ha−1 y−1). In each of these plots and in two control plots, foliage of four common tree species was collected immediately before each fertilizer addition. Trunk growth was measured in 105 individuals.

Foliar N concentrations were not significantly higher in trees fertilized with N compared to control trees. In Dendropanax cf. pendulus and Hedyosmum arborescens fertilization with N resulted in lower P concentrations but only after the third year of fertilization, possibly due to dilution by increased leaf production. Mean trunk diameter growth was significantly higher in the N-fertilized trees than in controls.

Mean foliar P concentrations were higher in Podocarpus urbanii and Clethra occidentalis following fertilization with P, but only after two years of fertilization. Trunk diameter growth was greater in the P fertilized plot.

Thus growth in some Jamaican montane forest trees was limited by the natural supplies of N and of P.

This paper examines the effects of irrigation practices and related activities on the environment and human health in the West Bank. Irrigated agriculture in the West Bank covers an area of 9,473 ha and utilizes 93 million cubic meters of irrigation water annually. The current annual use of fertilizers in the irrigated areas is 18,980 tons of chemical fertilizers and 198,900 to 265,200 tons of organic fertilizers. The total annual use of pesticides (excluding methyl bromide) in irrigated agriculture is 153 tons, of which 27 tons are internationally banned products. Methyl bromide is a dominant soil fumigant in the West Bank with a total estimated annual use of 400 tons, 44% of which is used on vegetables planted in plastic houses and high plastic tunnels. The soil solarization method to control soil-borne diseases is used by only 0.5% of the surveyed farmers. This study indicates that some farmers have suffered health problems due to exposure to pesticides, from the lack of protective clothing. Of the surveyed farmers, 19% suffer from poisoning symptoms and 1% are affected by methyl bromide fumigants. The total quantity of plastic sheets was estimated at 4,750 tons, at least 50% of which becomes waste. Eighty-eight percent of the surveyed farmers collect and burn the plastic wastes on the field, which could harm both the environment and human health through toxic fumes. Some water-related diseases occurred in the study area. Seventy-nine people were affected by leishmaniasis and 14 others by dysentery. Despite the heavy use of fertilizers, water quality analysis did not show high concentrations of nitrate.

Annual surveys of fertilizer practice have been conducted since 1942. Since 1985, nitrogen application rates to grass have progressively declined and phosphorus application has been reduced since the mid 1970s. Increasing environmental issues and the present interest in organic farming and low input systems indicate that these trends will continue. Present overall fertilizer use for grazing on dairy farms is about 170 kg N, 10 kg P and 20 kg К per ha. Higher rates are used for intensive silage production, 200 kg N, 15 kg P and 50 kg К per ha. In contrast, recommended applications are 340 kg N, 18 kg P and 25 kg К per ha for grazing and 380 kg N, 40 kg P and 260 kg К per ha for intensive silage. Herbage yield is controlled by the amount and timing of nitrogen fertilizer applications. The major mineral content depends on herbage maturity within the growth cycle; both phosphorus and potassium contents fall with declining crude protein concentrations.

Nitrogen fertilizer generally increases both magnesium and sodium concentration whilst potassium application decreases both. The overall effect of combined applications is to minimize changes. In the critical spring and autumn periods, herbage dry-matter intakes may be as important as magnesium content and availability when assessing the risk of hypomagnesaemia in the grazing cow.

Fertilizers, including phosphorus, even in the long term, have little effect on the calcium and phosphorus contents of herbage. Nitrogen and phosphorus concentrations are significantly ocrrelated in grazed herbage, silage and hay. If environmental or economic policies were to result in a reduction in the crude protein content of grazed herbage from ca. 250 to ca. 200 g/kg dry matter, the phosphorus intake of a cow giving 30 kg milk per day would fall by 0·5 g/kg dry-matter intake. This, together with any desirable additional magnesium, should preferably be given as an oral mineral supplement rather than by attempting to modify the mineral content of herbage.

Systems that reduce the use of fertilizers and pesticides are commonly said to do so by greater use of information and ecological understanding. However, this plausible proposition has not received much empirical examination. Different possible roles of information have not been clearly differentiated: in the development of new methods, in the farmer's decision whether to adopt them, and in their continued use. Also, the additional work that might be needed to handle information in reducedchemical systems often is not distinguished from the need for greater management ability. Typical procedures for evaluating the performance of alternative systems do not give enough attention to farmers' management ability and use of information. This is also true for research on conventional systems, even though in such systems information and management are not usually considered to have such a critical role.

The primary objectives of this study were to describe the various pest control and soil fertility management strategies used by North Carolina farmers and to characterize the types of farms and farmers using each strategy. In 1988, a survey was mailed to farmers who had shown interest in alternative methods and a randomly selected control group of conventional farmers. Cluster analysis on crops, inputs, and cultural practices used by crop farmers in the combined sample showed that they fall into three distinct groups. Very few members of the first group apply standard synthetic fertilizers and pesticides. Instead, more than three-quarters of them use cover crops, compost, organic mulch, commercial fertilizers and pesticides labeled as “organic”, resistant varieties, hand weeding, mechanical cultivation, scouting, and biological pest controls. More than half of the second group did not use any nutrient and pest management inputs or practices except synthetic fertilizers, herbicides, and lime. More than three-quarters of the third group reported use of synthetic fertilizers, synthetic herbicides, and lime, but also employed most of the cultural practices reported by alternative farmers. However, they less frequently used labor-intensive practices (such as manuring, mechanical cultivation, and hand weeding) and information-intensive practices (such as scouting and companion planting). Information sources, concerns about farm chemicals, and length of farming experience discriminated better than other socioeconomic factors and farm characteristics between farmers who use conventional chemical inputs and those who use alternative practices. Group 1 farmers differed from Group 3 farmers most sharply in that they rank the cost of pest control products and their extension agents' advice lower, have lower farm incomes, read more information sources promoting reduced synthetic chemicals, own more of the land they operate, and have less farming experience. The only factors significantly discriminating Groups 1 and 2 were that Group 1 fanners rank the importance of their extension agents' recommendations lower and effects of chemical products on birds and wildlife higher, read more reduced-chemical information sources, and have less farming experience.

Conventional agriculture is increasingly criticized as being too concentrated in ownership; too reliant on technology, petroleum-based inputs, and credit; too specialized and ecologically unsound; and too dependent on government subsidies. Alternative agriculture is offered by many as an alternative, and we discuss the possible impacts of its widespread adoption on farm income, yields, regions, labor, trade, environmental quality, and farm structure. The profitability of alternative agriculture is also examined - in so doing, a distinction is made between the adoption of low-input practices and a more holistic alternative agricultural system.

Livestock are important components of agricultural systems. In the U.S., one-half of total agricultural receipts come from the sale of livestock. They are the harvestors of range plants, forages, and crop residues; they level out the effects of the seasonally and variability of rainfall; they cushion disruptions in the trade and marketing of feed grains; they counteract declining soil fertility and soil erosion; and they contribute to the efficient year-round use of farm labor. Unfortunately, farmers are often not inclined to adopt alternative animal agriculture systems despite the advantages they may offer. Constraints that may be encountered include possibilities of reduced short-term profits, difficulties in adapting available technology to alternative farming systems, difficulties in shifting from specialized crop or livestock farms to crop/livestock farms, and the increased needs for labor and management. Some actions needed in the U.S. to improve livestock production in alternative farming systems are: the establishment of government policies to promote the shift of marginal lands to soil and water conserving crops and the incorporation of pastures and forages in crop rotations; research to improve the utilization by ruminants of ligno-cellulosic feeds (pastures, forages, crop residues); and programs to improve range and forest management and to lead to the development of systems that optimize the use of forages for the production of nutritionally desirable lean beef.

Recently there has been a change in thinking among many agricultural leaders and researchers toward a major focus on agricultural sustainability. To make progress toward such sustainability requires a clear delineation of its concepts and components. In this paper, I attempt to clarify relevant concepts and terminology in an effort to facilitate communication and cooperation. I also recognize, however, the intense feelings involved in these definitions. More satisfactory definitions will come in time as research and practice continue.