Cotton yields, quality, and insect abundance in the northern San Joaquin Valley, CA, 1996-2000: comparison between organic, conventional, and grower-led, reduced-input production systems

摘要

Beginning in 1996, the California BASIC (Biological Agriculture Systems in Cotton) Management Team has been testing and disseminating innovative ideas in cotton pesticide use reduction and organic production of cotton in the northern San Joaquin Valley of California. The team does this through an organized outreach program to enroiled growers in an area of owner-operator resident cotton farmers in Merced and Madera Counties, west of Chowchilla, California. The team is made up of cotton farmers, pest control advisors, agronomists, and researchers interested in risk reductive integrated pest management, novel production approaches, and marketing niches. Team researchers document field-level efficacy and suitability of alternative pest management options in the cotton production system, including natural enemy introduction and conservation for arthropod pest management; weekly monitoring of plant development, pests, and beneficial insects; and flame and mechanical weeding. BASIC growers also utilizeorganic acids and mineral nutrients as alternatives to conventional defoliants. In addition to in-season arthropod and plant growth monitoring,, each year we have analyzed production parameters including yield, fiber quality, pesticide use, and economics. These data are compared with values obtained for conventional cotton-producing cooperators in the same geographical area. A subset of enrolled BASIC fields is managed using certified organic techniques, and separate analyses of this group have also been done. We summarize here observational comparisons from the 1999 and 2000 field seasons and five years of yield and quality data relevant to the performance of BASIC-enrolled fields. Over all five production years, cotton yields of the conventional cooperators averaged 2.5 bales/acre. Five-year yields in non-organic BASIC fields were significantly lower, averaging 2 bales/acre. Differences were not significant in the individual years 1997, 1998, or 1999. Over all production years, average yields in organic BASIC fields were 1.7 bales/acre, and were also significantly lower than in conventional fields. County averages over this five-year period were 2.7 bales/acre. Key pest effects on boll retention in BASIC and organic fields have not been a production problem in any of the five years; boll retention percentage was not significantly different between production systems, although BASIC fields periodically showed higher abundance of mites and lygus bugs. Generalist insect predators were more abundantin organic fields than in conventional fields. Plant density at harvest was significantly lower in organic fields than either non-organic BASIC or convnetional fields, and this difference coupled with late planting dates (in 1996 and 1998), and an unusually early cutout (in 1997) may have contributed to observed yield differences between production systems.