Cultivated forages provide a controlled detritus based system that results in good crawfish yields.
Planting a cultivated agronomic crop is the most dependable method of providing suitable crawfish forage. It allows farmers to control the type and amount of available forage. Forage density is more predictable with an agronomic crop because cultural practices are well established.
The preferred forage to plant for crawfish is rice(Oryza sativa). Rice is grown for forage in most crawfish ponds in Louisiana. Rice has less of an negative impact on water quality than terrestrial plants because of its semi-aquatic nature and resistance to lodging. Rice can be planted for grain production with the post-harvest residue (stubble)and re-growth (ratoon) serving as crawfish forage, or it can be planted solely as a crawfish forage.
Factors to consider in rice variety selection include culture system (rotational or single cropping), forage biomass, lodging characteristics and rice re-growth (ratoon) potential.
Rice for Grain and Forage
Proper cultivation of rice requires adequate soil preparation, good planting techniques, water management and fertilization. A discussion of the cultivation practices required to optimize rice grain production is beyond the scope of this publication.
For more information on rice production, contact your county agent and ask for this LSU Agricultural enter publication: Rice Varieties and Management Tips, Pub. 2270.
Most rice farmers in Louisiana plant in late March to late April, with varieties requiring about120 days for grain maturity. Grain production is a function of the number of days required for heading, the planting date, temperature and photoperiod (length of daylight).
When harvesting grain, you can use a straw chopper on the rice combine to chop up the excess straw. These smaller pieces will decompose during the weeks before reflooding the ponds. If the combine is not equipped with a chopper, remove or disengage the spreader bars and allow the straw to fall directly behind the combine. If excessive straw is present, bailing the straw will enhance stubble regrowth and decrease water quality problems after flood-up.
The food supply for crawfish can be greatly increased by encouraging regrowth of rice stubble after the grain has been harvested. A light application of nitrogen (20-30 lbs of nitrogen/acre) can be applied immediately after the grain is harvested. The field should then be flushed if adequate moisture is not available. While holding more than 2-3inches of water for more than 48 hours is not recommended, timely flushing of the field will prevent the loss of nitrogen and encourage rapid stubble regrowth.
Rice for Forage
It is often desirable to grow a stand of rice as forage only. Such a rice variety should produce high vegetative biomass, be resistant to lodging, senesce slowly and persist throughout the crawfish production season. Also consider disease resistance, especially in late plantings.
This rice is normally planted from mid-July to early August. Planting rice as forage for crawfish at this time can cause a 50% reduction in total biomass. This results in good water quality, however, because the amount of decomposing straw is reduced at the time of fall flooding. Rice planted in August usually does not reach maturity, therefore scenes cense is delayed, and as a result its persistence may be better. Because extremely hot conditions can be encountered during this period, stand establishment is often difficult. Standing water on seedling rice during hot weather can kill the young plants by scalding. You must be prepared to remove all standing water from the young rice quickly.
It is desirable to cultivate a dry seedbed. A well-prepared seedbed will facilitate stand establishment if the rice is to be dry-seeded (either drilled or dry broadcast). Seeding rates of 75-90 lbs/acre for drill seeded rice and 90-120 lbs/acre dry broadcast seeded rice provide adequate vegetation. Harrowing after dry broadcasting may be desirable to cover the seed. If rain is not received within 3-4 days after planting, it may be necessary to flush the field (flood and drain quickly) to ensure adequate moisture for germination.
When water seeding, it may be beneficial to leave the seedbed somewhat cloddy. This will minimize seed drift, often be a problem in water seeded rice. The seedbed should not be left so cloddy that excessive weedy vegetation remains alive because these weeds will compete with the rice seedlings and lead to stand establishment difficulties.
Flood the field one to two days before seeding. Recommended seeding rates for water seeding are90-120 lbs/acre. If pre-sprouted seed is used, the field can be drained immediately after seeding in most cases. If dry seed is used, it is necessary to hold the flood for one day. This allows time for the seed to take in adequate moisture for germination.
It is necessary to drain the field in either case and 25beneficial to drain low areas to make sure all pockets of water are removed to guard against scalding.
It may also be necessary to flush the field to provide moisture within 7-10 days and periodically thereafter to maintain good soil moisture for optimum rice growth. These flushings should not last more than two to three days. Long flooding periods may encourage crawfish to emerge from their burrows and increase the possibility of losing young crawfish.
Even when rice is not grown for grain, it is necessary to provide fertilizer to assure good growth and development. Normally, about 60-80 lbs of nitrogen and 30 lbs of both phosphorus (P) and potassium (K) per acre are adequate with this system. On heavy clay river bottom soils, the P and K may not be necessary. A soil test is recommended for determining P and K needs. The fertilizer can be broadcast just before planting or applied just before one of the periodic flushes as the plants develop two to three weeks after seedling emergence.