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An increased knowledge of crop residue decomposition characteristics is a critical component for nutrient cycling studies in agroecosystems. Carbon and P losses from shoot residues of maize (Zea mays L.), wheat [Triticum estivum (L.), emend. Theil], soybean [Glycine TTIIlX (L.) Merr.], and shoot and root residues of crimson clover (Trifolium incarnatum L.) were compared in no-till and conventional till systems. Grain crop residues were generally collected from senescent plants following harvest and placed in fiberglass mesh litter bags. Soybean leaf residues, however, were sampled following preharvest abscission, while crimson clover residues were collected at spring anthesis and buried only in a conventional till system. Generally, the changes in C and P content of residues were best described by exponential and/or logarithmic functions. Losses of C and P from crop residues were consistently greater, and more rapid when residues were buried vs. left on the soil surface. Crimson clover shoots lost C and P more rapidly than root residues. Generally, greater initial losses of P than of C occurred in most residues. The lack of correlation between C and P losses is believed to be due to an inital and probably variable inorganic P content that is readily leached prior to the decomposition and mineralization losses of C. Differences in the rate and magnitude of C losses were related to seasonal effects, the initial N and P content, and/or the proportional amount of lignin in the plant residues. Tillage is clearly an important regulator or driving variable for element cycling in agroecosystems.

1998). Comparison of conventional and organic apple production systems during three years of conversion to organic management in coastal California.Abstract. Conventional and organic semidwarf Granny Smith apple production systems were compared during three years of conversion to certified organic management. Because of differences in fruit load with hand thinning compared with chemical thinning, apple tonnage was higher in the organic production system (OPS) in 1989 and 1991. The organic system was higher than the conventional system in number and weight of fruit per tree, but smaller in average fruit size. Using grower-receivedfarmgate premiums of 38% (1990) and 33% (1991) for unsorted, certified organic apples, comparative cost accounting showed greater net return per hectare for the OPS. The OPS required higher material and labor inputs in all years.Greater terminal growth in the conventional production system (CPS) in 1991 was the only significant difference in growth indicators between systems. N was generally higher in leaf and new wood bark tissues in the CPS. P was generally higher in the leaf and new wood bark tissues in the OPS. No decline in yield was associated with increased weed biomass in the OPS. There was no difference in fruit damage caused by codling moth between production system treatments (codling moth granulosis virus and pheromone-based mating disruption vs. synthetic insecticide). In 1991, secondary lepidopterous pests (apple leafroller and orange tortrix) caused greater fruit scarring in the CPS. In all years, tentiform leafminers caused greater leaf damage in the CPS. Apple leafhopper density and leaf damage were greater in the OPS in 1990 and Soil nutrient levels showed few significant changes during conversion to organic management. Soil bulk density and water holding capacity were useful indicators of changes in soil physical characteristics. Potentially mineralizable nitrogen andmicrobial biomass-C were more sensitive indicators of system change than total N or organic C. Two soil biological ratios, the respiratory ratio and biomass-C/total organic-C, were similar in the two production systems. Earthworm biomass and abundance increased in the OPS in the third year. The introduction of Lumbricus terrestris into the OPS greatly increased litter incorporation rates.

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The preparation, methods of purification, and physical properties are described of a large number of aliphatic monobasic esters of alkali hardwood lignin, from the acetyl through the stearoyl, and also of the dibasic esters of succinic, adipic, suberic, and azelaic acids. In general, the penta esters are formed with the lower acids, the tetra esters with the acids of medium molecular weights, and the tri esters with the higher acids such as palmitic and stearic acids. As a rule, the melting points of the products decrease with increasing chain length of the acid group as the products become more waxlike. All the esters of alkali hardwood lignin are quite soluble in acetone, chloroform, dioxane, and ethyl acetate.Solubility in methanol and ethanol decreases with increasing chain length of the fatty acid, whereas the solubility in ether and petroleum ether increases with increasing chain length. Esters of benzoic acid and p-toluenesulfonic acid have also been prepared, purified, and studied. One ester (the stearate) has proved to be an excellent mold lubricant for wood plastics. It is also soluble in drying and semidrying oils, and has been successfully incorporated in ink and paint formulations.k CYLATION of lignin and lignin derivatives has been usedfor some time as a means for determining the presence of hydroxyl groups in lignin and for their estimations. Thus, Willstátter lignins of various sources have been acetylated by Pringsheim and Magnus (16), Heuser and Ackermann (11), and Fuchs and Horn (9). Freudenberg lignin from spruce and beech was acetylated by Freudenberg and co-workers (6), and Brauns and Hibbert (S) acetylated partially methylated Will-stfttter and Freudenberg lignin. Freudenberg and Hess (7) reacted Freudenberg lignin with toluenesulfonyl chloride. All these lignin esters are as insoluble as the original materials from which they were prepared. Alkali lignin prepared from corncobs was acetylated by Phillips (IS)) that obtained from winter rye straw was benzoylated by Beckmann, Liesche, and Lehmann (1); and Marshall, Brauns, and Hibbert (IS) acetylated alkali lignin from spruce. These acetylated_ alkali lignins are soluble in organic solvents. Lignin derivatives, such as methanol, glycol, and phenol lignins, have been acylated to acetyl, benzoyl, p-bromobenzoyl, p-nitrobenzoyl, and p-toluenesulfonyl lignin esters (4), which are also soluble in organic solvents such as dioxane, pyridine, and acetone.A lignin of comparatively high purity (Meadol) is now available on the market (14). It is prepared from a soda black liquor from hardwood cooks. The crude black liquor is evaporated to a specific gravity of 1.1 and then contains 19-20 per cent total solids, of which about 60 per cent is organic matter and the remainder is soda ash. A portion of the lignin is precipitated

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Interest in reducing purchased chemical inputs to reduce production costs and avoid possible environmental damage prompted this 7-year study. Two management systems, current management practices (CMP) and reduced chemical inputs (RCI), were evaluated for four crop sequences from 1985 through 1992: continuous grain sorghum; continuous corn; a 2-year rotation of corn and double-cropped winter wheat and soybean; and a 4-year rotation of corn, winter wheat/soybean, corn, and red clover hay (changed in 1989 to a 3-year rotation of corn, red clover hay, and wheat/soybean). No-till planting and recommended rates of fertilizer and pesticides were used in the CMP system. In the RCI system, N was supplied by a crimson clover green manure crop or the red clover in the rotation. Weed control was by chisel plowing, disking, and cultivation.Crimson clover top growth accumulated from 70 to 180 kgN/ha, red clover from 77 to 130 kg N/ha. Rotating crops increased corn yield with CMP but not with RCI. lndry years, corn yields were low (less than 3000 kg/ha), corn did not respond to fertilizer N, and yields generally were higher with CMP than with RCI. With adequate rain, yield of all RCI treatments were the same as yield in CMP continuous corn receiving no fertilizer N. Johnsongrass competition was the main reason for low yields in the RCI treatments. Soybean yields were higher with CMP in 4 years and higher with RCI one year. Wheat and grain sorghum yields were higher with CMP than with RCI. A dramatic decline in johnsongrass in sorghum was noted in 1989, and several plots remained relatively free of johnsongrass through 1992.Management decisions made during the experiment included the degree of input reduction in RCI; whether to either end or modify unproductive treatments; whether to use newly available varieties and pesticides; whether to suspend the experiment to eliminate johnsongrass; and how to add new treatments while retaining the original treatments.