Benefits of nurse crops in potato production
Agriculture and Agri-Food Canada
Young potato shoots are vulnerable to drought, excess sun, wind erosion, and to being crowded out by weeds. New research from Agriculture and Agri-Food Canada (AAFC) has found the protection they need with ‘nurse crops’ – fast growing companion plants that help draw water to root systems, provide shade and shelter, and help keep weeds at bay.
"We already knew that cover crops help reduce soil erosion when planted in the fall after harvest," says Sheldon Hann, biologist at the Fredericton Research and Development Centre. "We wanted to see if planting a nurse crop would have a beneficial effect on potato growth and production during the growing season."
Nurse crops are planted in fields in the spring at the same time as the potato seed. "They are helpful because they grow quickly, increase the infiltration of water into the potato hill, and intercept rainfall until the potato shoots emerge from the soil," says Hann.
His study focused on the effects of field pea, winter rye, and spring barley as nurse crops to potatoes. To evaluate their value to potato production across the Eastern Canada, he collaborated with fellow AAFC researchers Dr. Bernie Zebarth and Josée Owen at the Fredericton Research and Development Centre, Sherry Fillmore at the Kentville Research and Development Centre, and Dr. Judith Nyiraneza at the Charlottetown Research and Development Centre.
Once the potato plants are established, the nurse crops provide another benefit by being tilled into the soil during hilling, creating green compost for the potatoes. Hann found that tilling winter rye and field pea into the soil helped retain soil moisture in the potato hill throughout the growing season, increasing the chance potatoes can survive drought conditions.
The study could be particularly good news in Eastern Canada where declining organic matter in the soil has led to declining potato yields and crops that are more susceptible to drought.
"Nurse crops can be part of the solution to the soil nutrient loss and drought conditions that have led to declining potato yields in Eastern Canada. When they are tilled into the soil, they act as green compost and help with water retention throughout the growing season. With better access to nutrients and water, we saw improved potato yields in some cases."- Dr. Judith Nyiraneza, Soil Specialist, Agriculture and Agri-Food Canada
"The key to good productive land is soil with high organic matter," says soil specialist Dr. Judith Nyiraneza. "Soil types in some parts of Eastern Canada can make it hard to keep that organic matter, and when you combine that with row crops that don’t leave behind a lot of plant residue and frequent soil tillage, you can quickly find yourself with depleted amounts of organic matter."
"Nurse crops can be part of the solution because they keep the ground covered during that critical window when the potato seeds have been planted and haven’t emerged," she says. "Before they become green manure themselves, the nurse crops keep existing soil organic matter in place and hold in the moisture, helping the potato plants to establish."
Dr. Nyiraneza adds that planting cover crops in the fall, using manure and other soil amendments, and rotating potatoes with other crops that leave behind a lot of plant residue, can also help increase soil organic matter.
Looking deeper into specific techniques, Hann and his team also found that potato yields increase when a high seeding rate is used for field peas and when a low seeding rate is used for winter rye.
- Nurse crops, planted as companion crops with potatoes, help draw water to root systems, provide shade and shelter, and help keep weeds at bay.
- Tilling nurse crops into potato hills increases moisture in the hill, providing a buffer against drought, and acts as green compost to increase soil nutrient levels.
- Identifying optimum seeding rates for nurse crops is a key factor in their ability to increase potato yields.
- The choice of species and the timing and methods of stopping the nurse crop growth are also important.
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