Comparison of conventional and organic apple production systems during three years of conversion to organic management in coastal California

Abstract

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.

Systematic method for rating soil quality of conventional, organic, and integrated apple orchards in Washington State

“…This agrees with other studies (Rice et al, 1996;Swezey et al, 1998) that found microbial biomass measurements to be more sensitive to management differences than SOC. The 1998 MBC measurements are, however, indicative of the significant increases in SOC in the integrated and the organic plots since 1994 (data not shown).…”

“…Similar results have been found in other studies (Gunapala and Scow, 1998;Swezey et al, 1998) comparing soils amended with compost or green manure to conventionally-managed soils. Given that all three systems have similar soil respiration rates (data not shown), the higher MBC levels in the integrated and organic systems could indicate long-term increases in SOC (Powlson and Jenkinson, 1981).…”

“…Swezey et al (1998) similarly measured lower soil bulk densities in organic apple orchard plots utilizing composted amendments as compared to conventional plots. The lower bulk densities measured in organic plots of this study are likely due not only to the addition of compost in 1995 but also to tillage in the 1997 and 1998 growing seasons.…”

“…Integrated farming systems, successfully adopted in some of the major apple growing regions in Europe (Sansavini, 1997), utilize methods of conventional and organic production systems in an attempt to optimize both environmental quality and economic profit. Although studies have found that alternative management practices may improve soil quality as compared to conventional management practices (Reganold et al, 1987(Reganold et al, , 1993Gunapala and Scow, 1998;Swezey et al, 1998), to our knowledge no study has specifically compared the effects of conventional, organic, and integrated management on soil quality in apple orchards. Doran and Parkin (1994) defined soil quality as "the capacity of a soil to function within ecosystem boundaries to sustain biological productivity, maintain environmental quality, and promote plant and animal health."…”

Spatial variability of microbial biomass and organic matter labile pools in a haplic planosol soil

“…The microbial activity of soil and the fractions of labile SOM are considered important indicators of the sustainability of management systems (malucHe-Baretta et al, 2006;FraiSSe et al, 1999;Swezey et al, 1998).…”