Organic Weed Management Using Designed Compost Extracts.

Organic farmers are interested in effective weed management techniques that reduce hand weeding cost and mechanical cultivation to enhance soil health and crop yields. In a randomized complete block design with four replications, a field trial was established to assess the use of chemically and biologically-designed compost extracts when applied pre and post planting and compared to mechanical cultivation- grower’s standard method in managing weeds. The objectives were to determine the effectiveness of compost extracts on weed density, crop yields of cabbage and lettuce and soil health. Cabbage ‘Tender Sweet’ seedlings were transplanted into two-row beds, spaced 76 cm between rows and 45 cm spacing within rows, whereas, head lettuce ‘Jericho’ seedlings were transplanted into three-row beds with 38 cm centers between rows and 45 cm spacing within rows at the Quiet Creek Farm in spring 2016. Results showed that in cabbage plots two applications of compost extracts followed by hand-weeding reduced Canadian thistle and ragweed weed density by 65% and 57%, respectively, while velvetleaf weed density was reduced by 77% and 68% when received one or two compost applications, respectively when compared to that in grower’s treatment. Compost application followed by two events of hand weeding increased cabbage yield by 25% and 35% in treatments with one and two compost extract applications, respectively, when compared to grower’s treatment. Tested treatments did no impact number of marketable head lettuce. However, lettuce marketable yield increased by 50% in treatments that received one and two compost applications followed by hand-weeding than those in grower’s standard treatment. There were no major changes in soil nutrients other than soil % organic matter was reduced 43% at end of the growing season.