Brassicaceae Cover Crops Affect Seed Germination and Seedling Establishment in Cucurbit Crops

Abstract

<jats:p>Field and laboratory bioassay studies were conducted to determine the impact of Brassicaceae cover crops on cucurbit germination percentages and stand counts. A 2-year field study in southwestern Michigan examined the effect of oilseed radish (<jats:italic>Raphanus sativus</jats:italic> var. <jats:italic>oleiferus</jats:italic>), oriental mustard (<jats:italic>Brassica juncea</jats:italic>), and yellow mustard (<jats:italic>Sinapis alba</jats:italic>) green manures on muskmelon (<jats:italic>Cucumis melo</jats:italic> Group reticulatus) stand. All three cover crops reduced direct-seeded muskmelon stand count as well as transplant survival. Stand count for direct- seeded muskmelon was greater than 85% for control and methyl bromide treatments and less than 41% for cover crop treatments. Oilseed radish had the greatest effect with 0% muskmelon stand in both years. The use of transplants improved muskmelon stand establishment. However, stand count (less than 45% to 50%) was still unacceptable. In bioassays, muskmelon, cucumber (<jats:italic>Cucumis sativus</jats:italic>), and honeydew melon (<jats:italic>Cucumis melo</jats:italic> Group inodorus) seeds were exposed to either non-lyophilized or lyophilized root and shoot aqueous extracts of oilseed radish. Germination percentages and radicle elongation measurements showed both extracts impacted all three crops to varying degrees. Muskmelon germination was least sensitive to the extracts, followed by cucumber, then honeydew. Cucumber and muskmelon root growth was equally inhibited by non-lyophilized shoot extract, while honeydew growth was mildly stimulated at 5% and 12.5% concentrations. Overall, non-lyophilized root extract showed stronger inhibition on seed germination than non-lyophilized shoot extract, while the reverse was true of lyophilized extracts. In general, non-lyophilized extracts had far greater impact on germination percentages and radicle elongation than lyophilized extracts. These results suggest species and tissue dependent toxicity of the cover crops as well as differential susceptibility of the cucurbit crops tested. Therefore, a plant-back period longer than the 8 days used in this study should be observed after cover crop incorporation before cucurbit seeding or transplanting.</jats:p>

Mustard Cover Crops for Biomass Production and Weed Suppression in the Great Lakes Region

“…When planted at the optimal date in the fall, mustard biomass was about 4 t ha −1 , whereas the typical range from spring plantings was from 2 to 4 t ha −1 . While some studies have found a similar range in mustard biomass in northcentral and northeastern United States (Stivers‐Young, 1998; Haramoto and Gallandt, 2005a; Ackroyd and Ngouajio, 2011), spring mustard biomass has been found to reach as high as 6.8 t ha −1 (Kumar et al, 2009). In both New York and Michigan, fall mustard biomass was generally greater with earlier planting dates, largely due to greater GDD accumulation.…”

Effect of defatted oilseed meals applied as organic fertilizers on vegetable crop production and environmental impact

“…Brassicaceae oilseed meals represent a particular type of meals; despite the similar N and phosphorous (P) content with respect to sunflower, no genetically improved seeds contain glucosinolates (GLSs) that through enzymatic hydrolysis via myrosinase produce a series of biologically active compounds (mainly isothiocyanates) (Fahey et al, 2001) that have shown an effect in controlling weeds (Ascard and Jonasson, 1991;Vaughn and Berhow, 1998;Vaughn et al, 2006;Rice et al, 2007), insect pests (Elberson et al, 1996(Elberson et al, , 1997, nematodes (Walker, 1996;Lazzeri et al, 2009), and soilborn pathogens (Smolinska et al, 1997;Manici et al, 1997;Mazzola et al, 2001;Chung et al, 2002). On the other hand, some authors demonstrated also significant allelopathic effects on seedlings of crops seeded after soil incorporation of brassicaceous crops with high GLS content (Jafariehyazdi and Javidfar, 2011), whilst for transplant crops, such as field vegetables, only minor effects on plant growth are reported (Haramoto and Gallandt, 2004;Ackroyd and Ngouajio, 2011). In any case the biocidal activity was clearly related to GLSs-type and concentration Vaughn, 1999;Bending and Lincoln, 2000).…”

Integration of summer and fall cover crops in vegetable cropping systems

“…In addition to identifying and establishing a suitable cover crop, another factor to consider is the planting date of the vegetable crop soon after termination of the cover crop. Ackroyd and Ngouajio (2011) suggested that planting too soon after cover crop termination decreased muskmelon yield (Cucumis melo) when using oilseed radish, oriental mustard (Brassica juncea), and yellow mustard (Sinapis alba). Certain cover crops have also been shown to decrease vegetable yield.…”

“…Little research has been done regarding the planting date of vegetable transplants after a cover crop has been terminated (Ngouajio, 2011) especially with the cover crops selected for this study. One reason to consider this parameter is the presence of allelotoxins from the cover crops.…”

“…if the planting date was too short (Ackroyd and Ngouajio, 2011). A planting date of two weeks is suggested for cover crops such as cereal rye (Secale Cereale) and ones in the brassica family (Ngouajio, 2011).…”