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Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/1/2016 Publication Date: 4/1/2017 Citation: Brennan, E.B. 2017. Can we grow organic or conventional vegetables sustainably without cover crops? HortTechnology. 27:151-161. Interpretive Summary: Producing vegetable sustainably is challenging because (1) typical production systems rely on intensive tillage, and relatively high amounts of irrigation and fertilizers, (2) large amounts of nutrients remain in the field in post-harvest residue, and (3) high land values where vegetables are often grow put economic pressure on growers to leave fields bare during winter periods when leftover nutrients can leach into ground water. Cover crops are crops that are grown to improve the soil and scavenge leftover nutrients, and are a recommended practice to help improve the sustainability of vegetable production. This paper outlines three novel cover cropping approaches to help vegetable farmers integrate cover crops regularly into vegetable rotations. Technical Abstract: Vegetable and fruit consumption patterns in the United States show that most people need to eat far more fruits and vegetables to meet the current nutritional guidelines for a healthy diet. Following these guidelines would require more than doubling the harvested acreage for fruits and vegetables and could have serious environmental implications if unsustainable production practices were used. This situation will likely intensify with population growth and climate change. To answer the title question, this paper focuses on the high-input, tillage intensive vegetable production practices in the Salinas Valley, a region often called ‘the Salad Bowl of America.’ This region has a serious nitrate pollution problem in the ground water that occurred as the agricultural systems here shifted from agronomic to high-value horticultural crops (primarily vegetables and strawberries) over the past several decades. This raises questions about the sustainability of past and current vegetable production practices and indicates the need for a radical paradigm shift in nutrient management here. Cover cropping is well-recognized as a ‘best management practice’ in vegetable production systems but is still relatively uncommon in many of the most important vegetable production regions in the U.S., including the Salinas Valley. It is argued that cover crops are an essential part of sustainable vegetable production because they provide a complex suite of unique services during fallow periods that complement best management practices during cash crop periods. The reasons that cover crop are uncommon here are discussed and three novel, alternative cover cropping strategies are proposed to potentially increase adoption in vegetable systems. These strategies are focused on reducing residue management challenges and include a novel proposal to extract the juice from nitrogen rich, immature cover crops for use as a liquid organic fertilizer in subsequent cash crops. |
