We monitored emergence of morning-glory, pigweed, and prickly sida from seeded populations in no-till plots with no debris (reference plots) or with crimson clover, subterranean clover, rye, or wheat debris. Cover crops were either desiccated by glyphosate or mowed and tilled into the soil. Debris levels, soil temperature, moisture, pH, nitrate, total phenolic acid and compaction were monitored during May to August in both 1992 and 1993. Seedling emergence for all three weed species ranged from <1 to 16% of seeds sown. Surface debris treatments delayed weed seedling emergence compared with the reference plots. Rye and wheat debris consistently suppressed weed emergence; in contrast, the effects of clover debris on weed emergence ranged from suppression to stimulation. Gfyphosate application resulted in a longer delay and greater suppression of seedling emergence in May than in April. In 1993, plots in which living biomass was tilled into the soil were also included and monitored. Weed seedling emergence was stimulated when living biomass was incorporated into the soil. Covariate, correlation and principle component analyses did not identify significant relationships between weed seedling emergence and soil physical and chemical characteristics (e.g., total phenolic acid, nitrate, moisture, temperature). We hypothesize that the observed initial delay of the weed seedling emergence for all three species was likely due to low initial soil moisture. The subsequent rapid recovery of seedling emergence of morning-glory and pigweed but notprickfy sida in the clover compared with the small grain debris plots was likely due to variation in soil allelopathic agents or nitrate-N levels. The stimulation of weed seedling emergence when living biomass was incorporated into the soil was likely caused by an increase in “safe” germination sites coupled with the absence of a zone of inhibition resulting from tillage.

We compared conventional and alternative systems for the establishment of apple trees on a replicated, whole-orchard scale. The alternative system consisted of a K-31 fescue sod rotation followed by planting of trees directly into sod that had been kitted with herbicide. The conventional system consisted of a standard corn rotation, accompanied by application of fertilizer and nematicide. Orchard floor management in the three years following tree planting was based on the use of both pre-and post-emergence herbicides in the conventional system and only contact herbicide in the alternative system. The study documented tree growth, pest incidence, and nitrate mobility in the two systems. The alternative system compared favorably with the conventional system for the growth and establishment of four apple cultivars. Many advantages accompanied the killed sod system, including less subsurface leaching ofnitrate-N and lower costs (largely from decreased herbicide use). The alternative system provided an economical alternative to the problem of soil organic matter depletion in conventional orchard soils without requiring increased use of commercial fertilizers. Grower concerns regarding increased potential for vole damage and poor initial tree growth were unsubstantiated.

Changes in soil physical and chemical properties following conversion from conventional to low-input farming systems could alter root growth in com and hence aboveground growth and yield. The main hypothesis we tested is that low-input and conventional farming systems produce different amounts of corn roots. We compared low-input and conventional farming systems, row position (row and interrow), and soil depth for effects on root length density in a Comly silt loam (Typic Fragiudalf) at the Rodale Institute Research Center in Kutztown, Pennsylvania. On all sampling dates studied (two each in 1989 and 1990) root length density under low-input farming systems was significantly greater than under conventional farming systems. We used analysis of covariance to correct for soil factors that could not be directly controlled. Soil water and bulk density had no clear effect on root length density. In contrast, there was significant covariance of soil organic matter with root length density on two of the four sample dates. Root networks were more dense in soil pockets rich in organic matter for every farming system, row position, and depth. These findings indicate that low-input farmers may be manipulating root production of corn to allow com to absorb more nutrients and water when water in the topsail is limited.

While crop rotations improve soil quality indicators and crop yields in humid temperate regions, much less information is available under harsher arid tropical and subtropical conditions. A field experiment conducted from 1990 to 1993 compared the effect of continuous pearl millet and pearl millet-fallow systems with six rotations of pearl millet that included one, two, or three years of a legume (cluster bean or mung bean). Data were collected on several soil quality indicators and pearl millet yield. Continuous pearl millet monoculture for three y ears did not affect soil organic C, NaHCO3-soluble P, DTPA extractable Fe, Cu, Mn, or Zn, or several soil organic N fractions, but slightly increased activity of dehydrogenase and acid and alkaline phosphatase enzymes. Similar trends were observed for fallow-based cropping systems, except that enzyme activities were lower. Cropping systems containing mung bean or cluster bean improved availability of soil N and other nutrients and increased enzyme activity. These effects increased with number of years of legume. Improvements from cluster bean generally were greater than from mung bean. The lowest pearl milkt yield was obtained with continuous pearl millet and no N, and yields f or fallow-based cropping systems were 13% greater than with continuous pearl millet. Grain yields of pearl millet with two or three years of mung bean in the cropping system were, respectively, 37 and 65% greater than for continuous pearl millet; with cluster bean the corresponding increases were 68 and 101%. Pearl millet yield increased with N applications up to 40 kg/ha under all cropping systems, and up to 60 kg/ha for some cluster bean-based systems. Yield of pearl millet following cluster bean was nearly double that of continuous pearl millet. These results indicate that in hot, dry climates cropping systems that include a legume, especially cluster bean, are more productive, use the limited water supply and fertilizer N more effectively, and improve several soil quality indicators more than do cropping systems without legumes.

Soil erosion is occurring at an alarming rate and threatens soil productivity and crop growth. A regional research committee was formed in the North Central region of the US in 1983 to develop a better understanding of soil erosion and productivity relationships on a broad geographic scale. This paper presents the history, project development and implementation and results of the committee, and a perspective on soil erosion-productivity research approaches. The original project included multistate field experiments on soils selected f or their local extent or agricultural importance. Erosion was classified as slight, moderate, or severe. Cropping practices were continuous corn or small grains, with cultural practices appropriate f or the area. The crop yields on moderately and severely eroded soils were consistently lower than on comparable slightly eroded soils. Precipitation and soil available water holding capacity were the factors most often identified as affecting yields. Other specific limitations were soil- or location-dependent. The most frequent soil limitations were depth of the mollic epipedon/topsoil, organic matter and clay content. Evolving objectives of the committee and state-based research emphases have provided additional information germane to soil erosion-productivity research. More than 40 papers have been published on soil properties, crop growth, management, and modeling as a result of this effort. The regional approach has fostered research on complex interactions among management and environmental factors and led to an increased understanding of functional relationships between soil erosion and productivity.