2013 ASHS Annual Conference

The benefits associated with cover cropping stand to enhance vegetable production through a variety of well-documented mechanisms. Although cover crops (CCs) have been shown to improve nutrient cycling, reduce soil erosion, and decrease certain soil borne diseases, some CCs have been shown to reduce emergence and stand establishment of both direct seeded and transplanted cash crops following their incorporation. Brassica family CCs have shown a particular tendency to reduce emergence due to the production of glucosinolate hydrolysis products following incorporation. It is hypothesized that these inhibitory effects are reduced over time following CC incorporation. The goals of this project were to (i) identify safe plant-back periods for sensitive crops after CC incorporation and (ii) evaluate the impact of planting date on muskmelon yields and quality. Experimental field plots were established at the Southwest Michigan Research and Extension Center (SWMREC) in Benton Harbor, MI. Six CCs were seeded at standard rates and included: oilseed radish (Raphanus sativus ‘Defender’), Oriental mustard (Brassica juncea ‘Forge’ and ‘Pacific Gold’), yellow mustard (Sinapis alba ‘Ida Gold’), oat (Avena sativa ‘Excel’), and a no cover control. Oat was used as a non-Brassica control. Following incorporation, C. melo cv. ‘Athena’ was seeded at 5-day intervals beginning with day 0 (immediately following incorporation) and ending with day 30. Crop emergence was recorded in each plot 15 days after seeding; muskmelon yields and fruit quality data were collected and evaluated by analysis of variance (ANOVA) and means separated using Tukey’s multiple comparison test (P ≤.05). The results of the time series analysis indicate that the optimal plant back period may be between 10 and 15 days after incorporation (DAI) depending on the CC. There did not seem to be a clear difference between the inhibitory effects among Brassica and non-Brassica CCs suggesting that the observed inhibition might be less related to Brassica allelochemicals than originally thought. Marketable melon yields were greatest for the 5 DAI planting and declined (along with fruit quality) the longer planting was delayed. These results indicate that while a longer waiting period is desired to maximize crop emergence following CC incorporation, muskmelon yields can be compromised when the growing season is narrow as it is in the upper Midwest.