Draining Ponds

In the previous crawfish newsletter (April 2012), we discussed stocking of crawfish. Crawfish ponds are drained and dried in late spring or summer to aid in planting forage and to rid the pond of predatory fish.

When mature, crawfish will burrow at the water/levee interface to initiate the reproductive process. Females that burrow into levees produce the majority of juveniles. In contrast, crawfish that burrow into pond bottoms as the last bit of water is drained from the pond will contribute few juveniles to the following season’s crop. For this reason, we recommend keeping the water in the pond as long as possible – and certainly until you observe active burrowing by females along the levees.

By now, you should be seeing considerable burrowing activity by crawfish along the water’s edge. By maintaining water in a pond as long as possible, even if harvesting has ceased, you allow crawfish to burrow when they are biologically ready.

Ponds should be dry two to four weeks before planting forage to allow sufficient time to prepare a tilled seedbed for planting. Drain the pond in stages over three to four weeks. Drain a quarter to a third of the water volume and hold it at that level for several days to a week. Then drain another quarter to third and maintain the water depth for another several days or a week. Repeat the process until the pond is dry.

Holding the water at a constant depth between water releases can assist females in excavating burrows in the levees. Ponds that are overpopulated with crawfish, although not a common sight this past production season, should be drained quickly to kill as many potential brood-stock as possible.  

 

Repair to Crawfish Pond Levees

We receive frequent inquiries about whether or not renovations to levees during the summer will potentially damage the following season’s crawfish crop.

Movement and compaction of significant amounts of soil on the interior of levees with heavy equipment after ponds have been drained and crawfish have burrowed will essentially seal crawfish in the burrows and prevent their emergence in the fall. So the simple answer is yes – extensive pond renovation can significantly reduce the following season’s crawfish crop.

Our general recommendation on levee renovations is, if at all possible, to complete the renovations in stages. For example, renovate a quarter to a half of the levees this summer and the remaining levees during the following summers.

If an entire pond is renovated, restocking will be necessary. After renovation, flood the pond again to an average depth of 6 to 9 inches and restock. (See April’s newsletter for restocking recommendations.) It is less likely healthy crawfish will be available for restocking the later into the summer any renovation occurs – if stocker-crawfish are available at all.

Retain water in pond as long as possible after restocking to soften the soil on the renovated levees and aid the crawfish in burrowing. A light disking of perimeter levees after renovation, but before refilling and restocking, may make it easier for newly stocked crawfish to construct burrows.

 

Considerations and Tips for Forage Planting for 2012-2013 Crawfish Crop Year

With the 2011-2012 crawfish season at an end for many producers, you need to plan for planting your upcoming forage crop.

Producers who farm crawfish behind a rice crop have fewer decisions to make, because their forage needs will be met by the established rice crop. Farmers who produce crawfish in ponds dedicated only to crawfish must first decide whether to plant a forage crop or rely on volunteer native stands of weeds and grasses.

When it is anticipated that the crawfish population density will be moderate to high, it is almost always advisable to establish a crop of planted forages such as rice or sorghum-sudan grass. Stands of volunteer vegetation often are unpredictable regarding the amount and type of vegetation that will be produced, and most volunteer stands are less desirable than planted stands, especially when crawfish populations are high. To achieve adequate stands of a planted crop, exercise care about the best timing and method of planting, as well as the type of forage to be planted.

The table below provides some guidelines about types of forage crops best suited to specific situations in a permanent crawfish (crawfish only) pond. Rice often is the preferred crop to use in a crawfish pond (assuming irrigation is available and an adequate seedbed can be prepared) even when there is no intention of harvesting the grain. A sorghum-sudan grass hybrid can be an acceptable substitute for rice, such as when irrigation water is difficult to obtain during the summer and/or when the optimum window for rice planting has passed, but sorghum-sudangrass may be a poor choice if not properly managed. Rice is more forgiving, but it sometimes can be difficult to get a good stand of rice in the heat of summer.

Whether planting rice or sorghum-sudan grass, time of planting is critical. In south Louisiana, the best time to plant rice is within the first two weeks of August, and for sorghum-sudangrass, within the last two weeks of August. Planting earlier usually will result in grain formation, an undesirable condition (unless waterfowl management is important). A later planting may result in reduced tonnage of forage produced.

Grain sorghum or millet should be considered only when waterfowl management is a primary focus and maximum crawfish production is not the principal goal. Preferred planting dates for these are similar to sorghum-sudan grass, unless grain production for the early teal season is needed. All grain types of forages are best planted in a tilled seedbed. Under some circumstances, such as where tillage or irrigation is not possible and/or where crawfish densities are expected to be low, it may not be worthwhile to invest in seeds and planting expenses. For low-intensity management, volunteer vegetation may be best the best option.

Although the level of management typically has more influence on the quality of the forage crop, the medium-grain rice varieties, in general, may have a slight edge over long-grain types in a crawfish pond. This may only be advantageous at high densities of crawfish and under the best management levels. Planting a mixture of rice varieties may even be better than planting a single variety. Recommended medium-grain varieties that are suitable to be planted for crawfish forage include Caffey, Jupiter and Neptune. Commonly used long-grain varieties include Cheniere, Catahoula, Cocodrie and Cypress.

With rice, as with other grains, stand establishment is the key to any good forage crop. Having good seed contact with the soil is important in achieving a good rice stand, and that usually requires a prepared (tilled) seedbed.

Because it may be difficult to achieve a good stand in the heat of summer, especially when the pond bottom is not level and contains pockets or “pot holes” that do not drain well, it is best to avoid water seeding unless you are experienced at planting that way.

Broadcasting dry seed on a tilled seedbed and lightly mulching or covering the seed often is the best approach, especially when rainfall is adequate and occurs frequently enough to avoid flushing (irrigating) the field.

Drill planting is another option. As with water seeding, when large areas of the pond retain puddles of water from irrigation during August, the water may be sufficiently hot to prevent or destroy stands of rice (“scalding”). Irrigation may be needed, however, if timely rains do not occur after planting.

As with any crop, fertilizer needs must be met, and damaging insects, such as army worms, must be controlled, but rice fields used in crawfish production do not have to be as weed free as is required for grain production. Some aquatic weeds are acceptable and may even be desirable as long as they don’t get out of control.

Harvested rice fields often will benefit from some nitrogen fertilizer and irrigation after the rice harvest to stimulate rice regrowth from the stubble (ratoon rice). Establish a very shallow flood on the stubble rice and replenish the water when total evaporation occurs. This provides moisture for rice regrowth and accelerates the breakdown of straw before pond flooding in October, which improves water quality after flooding. Ponds planted with one of the other grain crops should not receive a persistent flood until the permanent flood for crawfish is established (usually in October). A persistent shallow flood is advisable, however, for late planted rice once the rice is tall enough – as long as grass is not present in quantities that would deplete oxygen.

LSU AgCenter publication 2270, “2012 Rice Varieties and Management Tips,” has a wealth of information and guidelines for cultivating rice. This publication is prepared for rice grain producers, and the recommended planting dates for rice in it will be much earlier than what is recommended for planting rice as crawfish forage, but other management tips, including seeding rates, fertilization and pest management, are applicable when planting rice as crawfish forage.

Forage	Recommended when:	Not Recommended when:
Rice	- High crawfish densities are expected - Irrigation is available and dependable - Water can be put on or taken off field as needed - Pond bottom is mostly flat or leveled - Saturated soils exist or summer flooding can occur - Waterfowl use is desired	- Irrigation is not available during the summer - Prepared seedbed is not available (either by tilling or flooding) - Deep, permanent flooding is desired
Sorghum-sudangrass	- Irrigation is not available during the summer - Moderate or high crawfish densities are expected - Pond bottom is not flat or leveled but seedbed can be prepared - Soils are well drained - Deep, permanent flooding is desired	- Saturated soils exist or summer flooding can occur - Waterfowl use is desired
Grain Sorghum	- Irrigation is not available during the summer - Moderate crawfish densities are expected - Pond bottom is not flat or leveled but seedbed can be prepared - Soils are well drained - Waterfowl use is desired	- Saturated soils exist or summer flooding can occur - Deep, permanent flooding is desired - High crawfish densities are expected
Pearl Millet	- Waterfowl use is desired - Irrigation is not available during the summer - Low crawfish densities are expected - Pond bottom is not flat or leveled but seedbed can be prepared - Soils are well drained	- Saturated soils exist or summer flooding can occur - Deep, permanent flooding is desired - High crawfish densities are expected
Natural (Voluntary) Vegetation	- Irrigation is not available during the summer - Prepared seedbed is not available - Pond bottom is not flat or leveled - Low crawfish densities are expected - Saturated soils exist or summer flooding can occur - Deep, permanent flooding is desired	- High crawfish densities are expected

For more details on crawfish forage management and planting recommendations, see the Louisiana Crawfish Production Manual.  

 

Liming Crawfish Ponds

Prior to the time for planting forage for crawfish each year, we get a lot of questions about the need for or benefit of liming pond soils.

Crawfish have a need for calcium for shell formation, and many think harvesting crawfish from ponds over several or more years depletes the system of calcium. Repeated crawfish harvests do not deplete the soil and water of calcium, however.

We do not recommend that crawfish ponds or rice fields used to grow crawfish be limed – unless an LSU AgCenter soil analysis shows it is required for the vegetation being planted. Contact your parish LSU AgCenter Extension Service office for instructions on collecting and submitting soil samples to the LSU AgCenter’s Soil Testing and Plant Analysis Laboratory for analysis. The cost is $10 per soil sample. Area LSU AgCenter specialists can assist you in interpreting your soil test results. Contact information for all LSU AgCenter parish extension offices are on the AgCenter website.

For more information on this subject, read the article “Should I Lime My Crawfish Ponds”.

 

A General Guide for Using Salty Water on Crawfish Forage Crops

Salt water can become a problem for rice production in coastal parishes during dry years. A small amount of salt water is not dangerous to rice at any stage of growth. Higher concentrations, however, can affect production of forage and can cause a buildup of salt in the soil.

Crawfish have a higher tolerance for salt in the water than do any of the plants we recommend as forages.

Rice grown on soils relatively free of salt is tolerant to salt water with 35 grains per gallon (600 parts per million or 0.6 parts per thousand). Water containing more than this amount of salt cannot be used continuously throughout the growing season, or year after year, without damaging both the crop and the soil.

If sodium chloride or sodium carbonate has accumulated in the soil, less than 1,000 parts per million (1 part per thousand) is not toxic to germination of rice seed if there is normal soil moisture.

This table can be used as a guide for tolerance of rice to salt water.

Salt in Water (grains per gallon)	Salt in Water (parts per thousand)	Plant Stage of Growth
35	0.6	Tolerable at all stages. Rarely harmful and only then to seedlings after soil is dry enough to crack.
75	1.3	Tolerable from tillering through heading.
100	1.7	Harmful before tillering. Tolerable from jointing to heading.
200	3.4	Harmful before booting. Tolerable from booting to heading.
300	5.1	Harmful to all stages of growth. This concentration stops growth and can be used only at the heading stage when soil is saturated with fresh water.