The effect of organic soil amendments on soil pests and crop nutrition of broccoli

1996/1997

SB950.2.A2V6 1996/1997

In the third year of field work in Guatemala, Agrilab was involved with comparing broccoli from six different organic sources. The main objective was to compare the nutritional benefits and pest attraction of white grubs (a serious pest in broccoli) and Phyllophaga sp. (gallina ciega). The organic sources were green manure, cattle manure, home compost, and chicken manure in three different stages of compost. These were tested at high rates and low rates combined with low rates of chemical fertilizer based on soil test. Results from that third year showed no significant pest damage for any treatment, i.e. high quality broccoli was produced without any pesticide use. Dramatic differences were obtained on yield due to the nutritional status of the treatments. The best yields were produced by the high rate of chemical fertilizer alone (9.4 t/ha) and the low rate of chemical fertilizer combined with the low rate of chicken manure (9.5 t/ha). The same experiment was conducted in the fourth year and maintained the same objective. During the fourth year, much better yields were obtained, though no significant differences were obtained between treatments. The yields obtained for each treatment can be seen in Table 2. Again, there was no need to use pesticide to control pests, so the influence of the amendments on soil diseases and insects was not significant compared to the treatments using only chemical fertilizer. The soil test results conducted before and after the applications of the amendments showed no significant differences. The amount of organic amendments used by the growers show no significant difference to the higher rate. Interpretation of the soil analysis results showed that the fertility status of the soil might be good enough to get satisfactory yields and quality broccoli. Soil diseases and pests were also not a limiting factor through this trial.

no.4:129-132, IPM CRSP, ANNUAL REPORT

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