Outcome of Investigating the Impact of Green Manures and Weed Mat on Soil Biota and Tree Growth in Organic Peach Tree Orchards

The first years results revealed no significant trends in population changes in any of the faunal groups. There are probably several reasons why there were no significant changes in the faunal populations. One reason is that the peaches were planted into sites which had been fallow for more than one growing season. During this time the sites were not irrigated which resulted in a minimum amount of vegetation cover. Rainfall at the Rogers Mesa and Orchard Mesa site is not significant enough to encourage significant plant growth during the growing season. Thus there was insignificant amounts of organic matter being added back to the soil. Also, the fact that there was minimal plant cover in the plots, the soil was exposed to direct sunlight resulting in higher soil temperatures, and greater evaporation rates, which may have resulted in population declines in the microbial and macrofaunal populations.

During preparation of the plots for planting, the soil was ripped, followed by discing and rototilling. There have been several studies which have shown that traumatic soil disturbance can result in the destruction of habitat required for most microbial and microfaunal populations.

Soil sampling will begin the first week of April 2002 and continue every 4 weeks through the first week of September. A few additions/changes will be made to the experimental protocol. Soil moisture and soil temperature will be continually monitored with field data loggers in each of the four treatments. Also, the green manure will be weighed after cutting and prior to placement on the treated plots. In addition, the moisture content of the green manurewill be determined. Otherwise experimental protocol will be followed as outlined in the grant proposal.

OFRF suggested soil samples be taken to determine soil nutrient levels, but this would require a budget increase of $800 for the analysis of 32 soil samples (16 plots x 2 sites) for one sampling date. Soil samples for analysis should be taken in mid-April. Other than the soil analysis there will be no additional requests for a budget increase. An additional $3000 will be added to the project by R. Zimmerman to cover additional labor costs which were not foreseen in the original proposal This is the first study of its kind to be conducted on the western slope of Colorado. The information gathered from this study could improve soil management techniques for growers of perennial crops in semi-arid regions. We also feel that this study will provide a base for further granting opportunities and studies.

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