Individual study: The sustainable agriculture farming system project in California's Sacramento Valley
Poudel D.D., Ferris H., Klonsky K., Horwath W.R., Scow K.M., van Bruggen A.H.C., Lanini W.T., Mitchell J.P. & Temple S.R. (2001) The sustainable agriculture farming system project in California's Sacramento Valley. Outlook on Agriculture, 30, 109-116
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Convert to organic farming
A randomised, replicated, controlled study in 1989-1999 in northern California, USA (Poudel et al. 2001) (same study as Lanini et al. 1994) found that the density of weed seeds doubled (to 10,000 seeds/m²) in organic plots relative to conventional plots over the 10-year study period. Fewer root-knot nematodes Meloidogyne spp. were found in organic than conventional plots in 1994, but the degree of galling on tomato Solanum lycopersicum roots was similar between treatments. Average crop yields were similar in organic versus conventional plots for tomato (67 vs. 77 t/ha), safflower Carthamus tinctorious (2.4 vs. 2.7 t/ha), maize Zea mays (10.5 vs. 11.2 t/ha) and beans Phaseolus vulgaris (1.9 vs. 1.7 t/ha). However, early in the experiment tomato and maize yields were lower in the organic than conventional plots. Organic plots were more profitable (cumulative net income US$6,875/ha by 1999) than conventional plots (US$4,438/ha) when premium prices were applied, but the opposite was true without premiums for organic produce (a loss of US$-1,563/ha vs. a gain of US$4,438/ha). Organic plots were tilled to control weeds and conventional plots were treated with herbicides, pesticides and tilled. Treatments were replicated four times in 0.12 ha plots.