Assessing the effects of fall vs. spring plowing of red clover on nitrate loss in potato rotations

Session: 39. - Managing Agriculture Water and Nutrients - Science Solutions for Tomorrows BMPs

Yefang Jiang, Agriculture and Agri-Food Canada, [email protected]
Judith Nyiraneza, Agriculture and Agri-Food Canada, [email protected]
Mohammad Khakbazan, Agriculture and Agri-Food Canada, [email protected]
Brian Murray, Agriculture and Agri-Food Canada, [email protected]

Abstract

In Prince Edward Island, potato is commonly grown in rotation with grain underseeded with red clover (RC), with RC being plowed in the fall of the third year as green manure. Excessive nitrate leaching from this system has been linked to the contamination of drinking water and anoxic events in estuaries. An experiment (2014-2016) was conducted to explore if postponing RC plow from fall to spring reduces nitrate leaching, with varying N inputs to potato from 0 to 240 kg N/ha at an increment of 60 kg N/ha (0 N for RC) as a second factor. Lysimeter and soil sampling showed that significant nitrate leaching occurred after potato harvest under both fall and spring plowing, including 0 N input plots. The elevated nitrate leaching in 0 N plots was sourced from RC residues clipped in summer 2015, suggesting that much of the N released from the clipped RC was leached before being used by the potato plants. Nitrate leaching increased significantly with increasing N inputs, highlighting that fertilizer N contributed significantly to nitrate leaching. These data imply that managing RC residues in growing season and fertilizer N input to potato are more important than managing tillage timing to minimize nitrate leaching.

1. Keyword
drinking water

2. Keyword
eutrophication

3. Keyword
estuaries