Straw Chopping Research Articles

Cropping system influences on extractable water for mono- and double-cropped soybean

For rain-fed agriculture in the southeastern United States, efficient soil water use when double-cropping is essential. Water use by soybean [ Glycine max (L.) Merr.] following winter wheat ( Triticum aestivum L.) is, however, poorly documented. Winter wheat may deplete soil water, thus limiting subsequent soybean yield. Cropping system variables, such as soybean planting date and row spacing, may also affect water use. Therefore, a 4-year field experiment in northeastern Mississippi was conducted on Leeper ( Vertic Haplaquept) and Catalpa ( Fluvaquentic Hapludoll) silty clays. The objectives were to (1) determine the influence of soybean planting date, cropping system (monocropped versus double-cropped), and row spacing on extractable water (similar to available water) for soybean, and (2) identify a production system to improve the use of extractable water over a growing season. In mid- to late-May (the first soybean planting date), “Centennial” soybean in 38- or 76-cm rows was planted either between rows of standing wheat or in bare (monocropped) plots. After the wheat was harvested and the straw chopped, soybean was planted into bare soil or planted no-till into wheat stubble in mid-June for the second planting and in early July for the third. Soil water content was measured with a neutron probe from soybean emergence to maturity. Differences between each water content profile and a dry profile (constructed using the lowest recorded water content at each depth) were regarded as extractable water. Neither soybean planting date nor cropping system, as a main effect, exerted much influence on extractable water for soybean. As interacting factors later in the season, however, they were important. Plots with soybean in 38- rather than 76-cm rows contained more extractable water throughout the 1982 and 1983 seasons, and yielded over 9% more seed. Canopies closed about 20 days sooner with narrow rows than with wide rows. These full canopies protected and shaded the soil surface, probably reducing crusting and decreasing water losses by evaporation. We concluded that double-cropped soybean in 38-cm rows planted either into standing wheat in late May or into wheat stubble not later than mid-June utilized extractable water efficiently in silty clay soils in northeastern Mississippi.

Zum Problem der Strohmulchdecken im pfluglosen Ackerbau.

Agronomical Risks of Straw Mulch Covers in Reduced Soil Tillage Systems I. Influence of Chopping Intensity of Wheat Straw on the Liberation of Phytotoxins Phytotoxic effects of cereal straw are assumed to contribute to yield depressions of crops sown into mulch covers. Leaching of straw-derived phytotoxins and their inactivation in soil may be accelerated by cutting harvest residues into short pieces combined with destroying the tubular structure of cereal straw culms. In model trials, conventionally (mainly transversally) and intensively (transversally plus longitudinally) chopped winter wheat straw was leached before and after aerobic rotting processes had started, and the aqueous extracts were analysed for phytotoxicity in bioassays with curly cress (Lepidium sativum L.). The concentrations of four selected phenolic acids (para-hydroxy-benzoic-, vanillic-, t-ferulic- and t-para-coumaric-acid) were determined by HPLC-technique. High toxin concentrations were detected only in extracts of undecomposed straw. Toxin liberation decreased from very high rates at the beginning to low rates after 60 hours of extraction. Intensively chopped straw released more phytotoxins than conventionally chopped straw during the first 4,5 hours of extraction. Subsequently, no differences in toxin liberation rates were observed. These results were confirmed by the phenolic acid analysis. To conclude, intensive chopping of straw exhibited no advantages with respect to straw derived phytotoxicity. The absence of allelochemicals in extracts of aerobically rotted straw indicates that under normal field conditions at Gottingen toxic effects from winter wheat harvest residues are of low importance for subsequent crop growth.

Presence of endotoxins in different agricultural environments

Gram-negative bacterial endotoxins are contaminants of dusts from agricultural products. They represent a potential health hazard for farmers working in many different processes. However, the occurrence of endotoxins has not been well characterized in the various farming operations. Therefore, two farming activities with potential for generating airborne endotoxins were studied: 1) chopping of baled corn stalks or straw for bedding in New York State, and 2) oat bin unloading in Alabama. Actual airborne endotoxin levels in dusts obtained during bedding chopper operations far exceeded [90 endotoxin units (EU)/m3] the level at which acute pulmonary function decrements occur in cotton dust-exposed individuals. Endotoxin contamination of laboratory-generated dust from an oat sample likewise exceeded these levels. This study documents the presence of potentially hazardous exposures to endotoxins in two common farm processes, which expands the knowledge of airborne endotoxin exposures on the farm.

A review of the mechanical behaviour of straw when compressed to high densities

The present state of knowledge is reviewed concerning the high density compression of straw in relation to the production of briquettes for fuel or other purposes. Consideration is given to the extensive body of experimental data and theoretical analyses of the mechanics of the compression of fibrous materials. The available information on the formation of high density briquettes in closed and tapered dies is discussed. The information is classified under four broad aspects, namely: (1) the physical properties of straw, (2) the compression characteristics, (3) the formation of briquettes, and (4) theoretical considerations of compression. The many variables involved are discussed in relation to die pressure, specific energy required and the relaxed density and durability of the straw briquette. Particular attention is given to factors of briquette formation such as die size, die charge, maximum pressure, dwell time, straw chop length and moisture content, and type of straw. Some consideration is given to relevant information from work on the compression of grass and lucerne. Work on the effects of temperature and additives is considered and the mechanism of briquette formation discussed. The theoretical work on the compression of fibrous materials in dies is examined in relation to empirical formulae relating pressure and density. These include studies of pressure distributions within the material and rheological models based on spring and damper elements. The value of approaches using dimensional analysis and multivariate analysis is also discussed. Areas of work are identified where further research is required to advance the design of machines for producing high density straw briquettes.