Cover crops conserve water, revitalize land
CLEMSON – Growing noncash crops, such as crimson clover and winter rye, can be time-consuming and labor-intense but the rewards can be oh so sweet.
These two crops, plus growing other brassicas, grasses and legumes and using no-till methods for growing produce can help revitalize the land on which cash crops are grown. This was what a group of growers learned from Clemson University experts during a recent workshop on the Clemson campus. The workshop was organized by the Clemson Sustainable Agriculture Program with support from the Southern Region Sustainable Agriculture Research and Education (SARE) Program.
“No-till vegetable production offers a more sustainable approach to weed management than the frequent use of herbicides and tillage,” said Kelly Flynn, associate coordinator for Clemson’s Integrated Pest Management and Sustainable Agriculture program. “It also promotes soil health. Because cover crop based no-till vegetable production involves a different approach to management, growers may be reluctant to transition from conventional tillage without seeing the system in action and knowing its costs and benefits compared with conventional tillage.”
The workshop consisted of presentations by professors and researchers in Clemson’s College of Agriculture, Forestry and Life Sciences, as well as Cooperative Extension Service and a private consultant. These experts’ recommendations were based on current research and experiences in the field over the past decade.
Bhupinder Farmaha, a researcher at Clemson’s Edisto Research and Education Center in Blackville, talked about how cover crops can be used for management of soil, water, pests and nutrients. He discussed issues related to soil compaction in South Carolina and how it can limit root penetration which reduces crop yield.
“For good crop growth and yield, the compacted layer must be broken,” Farmaha said. “Farmers in the southern United States rely heavily on the use of annual deep tillage before planting. But there is a lot of interest in using cover crops to adopt a no-till system for production.”
Farmaha shared several results from the studies conducted by Ahmad Khalilian at the Edisto REC over the past decade. He explained that deep-rooted cover crops such as such as rye and tillage radish can penetrate the compacted layers and improve the crop growth. Tillage radish, or daikon radish produces a large taproot that penetrates compacted soil layers to increase soil aeration and water infiltration. This decreases soil compaction and allows for roots of successive crops to penetrate deeper in to the soil.
This strategy can also help in reducing the frequency of deep tillage from annually to once in every 2-to-3 years depends upon the severity of compaction.
Farmaha also talked about the benefits of using cover crops in weed and nutrient management strategies. Several cover crops can be used in these types of strategies. Determining which cover crop to grow depends on what outcome is desired. If more nitrogen is needed, Farmaha said to plant crimson clover or hairy vetch. Planting rye or black oats, triticale or wheat can reduce weed pressure, he said, adding more research needs to be done to determine how the inclusion of cover crops impacts the fertility decisions of cash crops.
Mark Schonbeck, a consultant with the Virginia Association for Biological Farming, said cover crops are farmers’ “Number One” tool for building healthy soils.
“Cover crops help keep carbon flowing from the atmosphere to the soil,” Schonbeck said. “Cover crops also help protect the soil surface, build soil organic matter and enhance soil structure, as well as feed the soil, promote beneficial organisms and open and deepen the soil profile.”
Schonbeck also touted using no-till methods in vegetable production.
“It’s important to minimize soil disturbance,” he said. “Growers also can energize the soil system by using crop biodiversity such as crop rotation, intercropping, growing several different species of cover crops and using livestock-crop integrated systems. Applying these principles, as well as using cover crops to keep the soil covered as much as possible year around will help maximize roots living throughout the soil all year.”
Soil health is key to organic farming.
“Organic farmers rely on tillage, cultivation and cover crops to manage weeds,” said Schonbeck, adding crop diversification and reduced tillage can help enhance soil health.
David Robb, Clemson Student Organic Farm manager and research associate, said weed management and associated labor costs are one of the biggest challenges for organic vegetable production. The use of organic no-till practices for summer vegetable production at the student farm began being used in 2014. Roller crimping is used to terminate cover crops.
“We used to rely heavily on soil tillage and other forms of soil cultivation for weed management at the student farm,” Robb said. “We’ve found no-till mulches provide adequate weed suppression early in the cropping season. But, establishing good stands of cover crops can be difficult. Seeding timing can be tricky and, for us, using no-till practices is vegetable crop specific.”
Robb also said nitrogen management in no-till at the student farm is “…still a bit of a mystery” and transplanting into no-till is a challenge.
In addition to helping improve soil health, cover crops also can be used to conserve soil moisture. Ricardo St. Aime, a Clemson graduate student working with Sruthi Narayanan at the Department of Plant and Environmental Sciences, said drought frequency and intensity have increased in South Carolina over the past 25 years.
“Irrigation systems can be costly,” St. Aime said. “A study by Clemson irrigation specialist Jose Payero shows an irrigation system consisting of a center pivot, pump and well can cost $2,000 per acre for corn. An irrigation system for broccoli in Lexington cost $300.24 per acre in fixed costs and $100 per acre in variable costs. Cover cropping can help alleviate these costs.
Cover cropping is gaining importance as a sustainable whole-farm system approach to improve agricultural productivity.
“We found that none of the seven cover crops including grasses, legumes and brassicas as single species or mixtures evaluated in our study in the upstate of South Carolina depleted soil moisture,” Narayanan said. “Interestingly, a five-species legume-grass mixture produced the same amount of biomass, compared to rye, that too with conserving soil water for the next cash crop.”