Cover Crops for Sweet Corn Production in a Short‐Season Environment

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Abstract
Legume cover crops can supply all or most of the N required by a subsequent crop if legume biomass is of sufficient quantity and N mineralization is approximately synchronous with crop demand. Three 2‐yr crop rotation cycles were conducted on a Lamoine silt loam (fine, illitic, nonacid, frigid Aeric Epiaquept) soil in Maine to (i) evaluate biomass and N accumulation of alfalfa (Medicago sativa L.), winter rye (Secale cereale L.), and hairy vetch (Vicia villosa Roth subsp. villosa) plus winter rye cover crops; (ii) determine sweet corn (Zea mays L.) response to legume and fertilizer N sources in a barley (Hordeum vulgare L.)–sweet corn rotation; and (iii) assess the accuracy of the presidedress soil nitrate test (PSNT) and leaf chlorophyll N test (LCNT) for distinguishing N‐responsive and nonresponsive sweet corn. Both legumes accumulated more N than rye grown alone, although total biomass was similar. Sweet corn following rye always exhibited a linear response to N fertilizer (up to 156 kg N ha−1), but generally exhibited no response to added N following either alfalfa or hairy vetch plus winter rye (VR). Both PSNT and LCNT were 75% accurate in identifying plots responsive to additional fertilizer N. The legume cover crops grown were able to replace all or nearly all of the N fertilizer required by a subsequent sweet corn crop, with fertilizer replacement values (FRVs) of 58 to 156 kg N ha−1 in a short‐season environment. These cover crops are a viable alternative source of N, greatly reducing or eliminating the need for N fertilizer.