Presentations 2016

Assessing the effects of buckwheat as a wireworm control crop on groundwater quality

Agriculture and Agri-Food Canada

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Potato production plays a significant role in the economy in Prince Edward Island (PEI), Canada. However, high levels of nitrogen leaching losses from the potato production systems have been linked to the contamination of groundwater and associated surface water. While the industry is facing unprecedented pressure to mitigate these environmental impacts and maintaining its market competiveness, it is also being threatened by increased wireworm damages on potatoes. Rotating potato with buckwheat has been promoted for wireworm control as potato tuber damage by wireworm is significantly reduced following a buckwheat crop. A study is being conducted to evaluate the effects of growing buckwheat in rotation with potato on groundwater quality. Five three-year potato rotations were initiated in 2014, including two current industry standards: barley under-seeded with red clover-red clover-potato (T1), and barley under-seeded with timothy-timothy-potato (T2), which are compared to buckwheat-based cropping systems, each consisting of two years of buckwheat but with different buckwheat plant termination methods; buckwheat-buckwheat-potato with buckwheat terminated midseason through mowing (T3), buckwheat-buckwheat-potato, with buckwheat terminated through disking (T4) and buckwheat-buckwheat-potato with buckwheat grown for grain (T5). The experiment of random blocked design was implemented at Harrington Research Farm of Agriculture and Agri-Food Canada (PEI) with each treatment replicated three times on an experimental unit of 6 by 8 m. A stainless steel suction lysimeter (manufactured by Soil Moisture Systems, SW-071-260) was installed in each plot at a depth of 80 cm for collecting soil water samples. Soil water was sampled weekly using a pressure-vacuum hand pump with gauge when the soil was saturated or/and after each rain event for measuring nitrate, nitrite, and ammonium. Anion Exchange Membranes (AEMs) were deployed in each plot at depths of 10 to 15 cm and replaced monthly to track soil nitrate. Composite soil samples were collected from each plot at depths of 0-15, 15-30, and 30-45 cm, respectively, before planting and harvesting every year. The soil samples were analyzed for nitrate, ammonium, total C, and N. Two soil moisture and temperature probes (Hobo, S-SMA-M005) were deployed at depths 0.2 and 0.3 m for measuring soil moisture and temperature in two selected plots. Preliminary soil water nitrate measurements from 2014 showed higher time-averaged concentrations in T4 (11.4 mg N/L, ±6.1) and lower in T5 (3.8 mg N/L, ±1.7). AEMs data showed a similar trend towards lower nitrate under T5 with 0.28 mg N/cm2 /d. This study will show if growing buckwheat in potato rotation can reduce nitrate leaching compared to the industry standard potato rotations.