Louisiana: With Cover Crops, Pin Down Your Objective First

Fertilizer application on cover crop. Photo: Alabama Cooperative Extension

Corn harvest is in full swing across Louisiana, and soybean harvest has begun on a limited basis. As we move into the fall months, now is the time to begin planning your winter cover crop management strategy.

Cover crops are used for several purposes, including protecting soil from erosion, improving soil structure, scavenging and cycling of soil nutrients, increasing organic matter, helping alleviate hardpans, etc.

Cover crop selection will depend on the goals a producer would like to accomplish by planting a winter cover crop. Having a clear objective for planting a cover crop will also aid in cover crop management.

For example, if minimizing soil erosion is the main objective, a cereal cover crop would be a good choice. The fibrous root system of cereals will help prevent topsoil from leaving the field.

Cereal winter covers are good nutrient scavengers, as well. In contrast, a tap-rooted cover crop like forage or tillage radish (woolypod vetch, red clover, etc.) is better suited for deep nutrient scavenging and potentially aids in loosening a soil compaction layer or preventing one.

Mixes of cereal and legume covers can reduce early-season N fixation issues in corn. Preliminary data collected by AgCenter scientists have shown that in soybeans, legume cover crops can supply N for early growth needs until nodules develop.

Other important considerations when selecting a winter cover crop include the cash crop to be grown following cover crop termination and winter cover crop termination.

Be sure to plant only quality seed, which will help eliminate weed seed contamination issues. When planting legumes, make sure the rhizobium inoculant strain is correct for the legume species that will be planted, and always inoculate.

If planting pre-inoculated legume seed, get pure live seed per pound and adjust seeding rates accordingly. Some pre-inoculated seed is larger and therefore has less pure live seed per pound.

Seeding Rate Considerations

Seeding rates of cover crops will depend on the seeding method and date of sowing and whether the land is enrolled in a CSP or EQIP program. For cereals, avoid low seeding rates and establishment methods that could lead to spotty emergence.

Spotty emergence could cause the cereal to “bunch” (a single plant with multiple tillers and large root system), which could lead to main crop establishment issues such as skips and variations with seed placement depth and seedling emergence.

Cover crops should be planted as soon as possible following the main crop harvest. When planted earlier in the fall, growth and biomass production will be maximized prior to cold weather, which will slow the growth and development of the cover crop.

Planting your cover crop soon after harvest is especially important if corn will be planted. Early cover crop termination when planting corn combined with late planting of a cover crop (November) will reduce overall biomass production, therefore minimizing the benefits of the cover crop.

Legumes are generally slow-growing if planted too late (November), and biomass production will be minimal prior to the onset of cold weather.

NRCS – The Fine Points

If fields are enrolled in an NRCS conservation program that requires cover crops, be sure to follow the NRCS’s cover crop guidelines. NRCS seeding rates and planting dates for common cover crops grown in Louisiana can be found at this link. The planting window for most winter cover crops is Oct. 1 to mid-November.

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Ranges for average first frost dates for Monroe, Shreveport, Alexandria and Baton Rouge are Nov. 15, 18, 19, and 29, respectively.

The AgCenter website has some useful tools that may aid in further refinement of accomplishing the intended goals for your farm, including potential scenarios and their implications for incentives payments and a Q&A on conservation policy and crop insurance.

NRCS payments for cover crops change from year to year. Updated numbers are included in the decision tool located here in estimating overall costs of cover crops implementation.


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