Feasibility of organic production of sweet corn and snap beans for processing

Nutrient and weed management are two hurdles to large-scale organic vegetable production. Research was conducted to compare weed and nutrient management tactics, allowable in organic production and feasible on large hectarage for sweet corn and snap beans for processing. Weed management tactics such as rotary hoe, inter-row cultivation and a stale seedbed were evaluated alone or in combination. Handweeded and herbicide-based treatments were included for comparison. Organic weed management was feasible in snap beans with yield similar between treatments with inter-row cultivation and the herbicide treatment in all three years of the study. Organic weed management was more difficult in sweet corn, the treatment involving three inter-row cultivations was the only one consistently similar in yield to the herbicide treatments. Sweet corn nutrient management was the focus of this research due to high nitrogen (N) requirement of the crop. Composted poultry manure (CPM), green manure (GM) crops (alfalfa, rye and pea) and organic high-N fertilizer were used to deliver full (168 kg/ha), half (84 kg/ha) N rates to the sweet corn crop. Ammonium nitrate was used as a conventional fertilizer for comparison. Results were highly variable among years in the organic programs due to variability in organic N mineralization. Utilization of the high-N organic fertilizer resulted in the most consistently high yields among the organic programs, although this product is costly. Alfalfa provided a significant N credit to the sweet corn crop but pea did not. A combination of alfalfa and the organic fertilizer maximized yield while minimizing cost to the grower. We found no evidence of residual N availability when snap beans were produced on the research plots following the sweet corn. A laboratory study conducted to evaluate the mineralization of the various N management programs confirmed that the amendments were fully mineralized during the cropping season. The rate of mineralization of the high-N organic fertilizer closely matched the mineralization of the ammonium nitrate while the mineralization rate of the CPM was out of sync with crop need. The lab study further confirmed that the alfalfa GM crop should receive a significant N credit while pea should not.