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Toward sustainable nitrogen management in vegetable production: balancing yield and nitrogen use efficiency




Farzadfar, S.
Taylor, J.M.
Knight, J.D.
Congreves, K.A.

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Cover crops (CC) have the potential to immobilize nutrients, especially nitrogen (N), that would otherwise be lost during post- or pre-harvest periods, leading to improved N management. However, information on how CCs influence N management for vegetable production are scarce. This study aims to determine agronomic responses (yield and N use efficiency, NUE) of three common prairie vegetable crops when produced with and without an overwintering rye CC. In 2017 and repeated in 2018, trials were initiated on a Sutherland clay soil (Dark Brown Chernozem) in Saskatoon for a fully phased broccoli-sweet corn-carrot sequence, with each crop type receiving five N fertilizer treatments (ranging from 0 to 300 kg N ha-1) arranged in a randomized complete block design with three replicates. After harvest, sub-plots were established with vs without a shoulder-season rye CC, and the effect followed into the subsequent growing season. Compared with zero N control, N fertilizer rate did not affect vegetable crop yields in either year, demonstrating the N-rich nature of the soil at this site. Depending on the crop, moderate to high application rates of N significantly reduced crop NUE; N rates above zero N control reduced NUE for sweet corn, rates above 75 kg N ha-1 reduced NUE for broccoli, all rates above 55 kg N ha-1 reduced NUE for the root crop in 2018. Subsequent to the CC in 2018, we found no N fertilizer by CC interaction for crop yields or NUE. The rye CC had no effect on crop yield or NUE for sweet corn or carrot, but significantly reduced broccoli yield and NUE. Regression analysis showed a decreasing trend in NUE with increasing N rates for all three vegetables, regardless of the CC. Our results suggest that the repetition of this experiment for a number of years is necessary to avoid excessive N application and improvement of productivity with cover crops.










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Soils and Crops Workshop