Residue Utilization and
Management-69
 
 

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In the fall of 1963, straw management treatments were begun at Biggs on a field planted annually to Colusa rice. Straw from the previous crop was burned or returned to the soil, and the rice crops were fertilized at 0, 40, 80, and 120 pounds of nitrogen per acre. All treatments were repeated in four successive years in six replications, and the plots were large enough to permit machine harvesting. Average yields over the five growing seasons show no difference between the two methods of handling the straw at any of the levels of nitrogen applied. The experiment is being continued, and fall vs. spring incorporation and burning treatments are being studied.

A. RICE RESIDUE INCORPORATION

One laboratory study and two field studies aim to determine the influence of soil type, nitrogen content of soil, aeration, and straw load on rate of rice straw decomposition. The study is being conducted at relatively low ambient air temperatures (55 F day and 45 F night). The results will determine what treatments will be selected for field investigations in the fall o f 19 70 .

Soil samples have been collected from assigned basins at Davis and from Butte County. These samples are in the process of being analyzed. They represent time zero (no treatment effect), and are required to evaluate treatment effects.

B. RICE STRAW HARVESTING AND PACKAGING

Progress and results are as follows:

1) Packaging of rice straw for feed or fiber. Preliminary work with a field cuber demonstrated that rice straw can be cubed when mixed with certain types of binders. The straw must be dry, probably 10% moisture or less. Further work with ground straw indicated that the physical condition of the straw, as well as the type and amount of any binders or other feed materials, affects cubability. A full-scale pilot cubing plant installed at Davis is available for intensive study of these variables.

2) Economic evaluation of various straw harvesting and packaging systems. Cost studies are nearing completion for the following systems of straw utilization or disposal:

   a) Field baling and stockpiling,

   b) Field cubing and stockpiling,

   c) Stationary cubing, mixed with other feed ingredients.

   d) Total crop harvest concept, including field chopping, hauling to dryer, dehydrating, cubing, cooling, and stockpiling.

   e) Incorporating straw in the soil. Results are incomplete but will be available soon in report form.

C. RICE STRAW FEEDING

Research on the feed value of natural and processed rice straw in 196970 has been in four areas: 1) a review of literature on the composition and value of rice straw as an animal feed; 2) chemical analysis of several samples of California rice straw to compare with literature values and make estimates regarding potential use; 3) preliminary palatability trials with rice straw containing rations for cattle; and 4) planning future animal feeding experiments with rice straw.

The literature survey, essentially complete, will be reproduced for distribution. The survey indicates that unprocessed rice straw is a typical low-quality roughage (av. TDN, 43.4%; digestible protein, 1.0%; Ca, 0.2%; P, 0.l%) which could provide a maintenance subsistence for ruminants if deficiencies in protein and minerals were satisfied. Alkali treatments were generally effective in improving rice straw digestibilities.

Chemical analysis of California rice straws (including Earlirose, Colusa, Bluebelle, Calrose, and some samples not identified by variety) shows no great deviation from the typical variation found in the literature. Crude protein varied from 5 to 6%; ash, 15-18%; silica, 13-15%; lignin, 4-5%; crude fiber, 28-36%; Ca, 0.15-0.29%; P, 0.09-0.14%.

The animal palatability trials show that cattle will consume balanced rations containing up to 807, rice straw. Cubing or pelleting has an influence on consumption, with animals generally eating more of the pelleted straw ration.

A contract is being negotiated between the U.S.D.A. Western Utilization Research and Development Division, Albany, California, and the Department of Animal Science to conduct a series of animal feeding experiments with cattle and sheep. These funds will be used to extend the scope of the preliminary experiment previously planned. Four experiments have been outlined: 1) A digestion trial with sheep, using natural and alkali processed rice straw in milled or pelleted form. 2) A more extensive sheep-feeding experiment involving rice straw processed under a variety of conditions chosen on the basis of maximum in vitro digestibility. This experiment will measure animal growth, digestibility, and net energy value. 3) Growing-fattening beef cattle, with weight gains, fed efficiency, carcass data, and energy utilization being the major criteria of response. The ration fed in this trial will be selected from the treatments showing most promise in earlier experiments. 4) A test with cattle, that is similar in design but with the details of rations and treatments to await the results of the previous experiments.

D. METEOROLOGICAL CONDITIONS FOR RICE RESIDUE BURNING

In April 1970, funds became available for investigating smoke dispersal during field burnings in the Sacramento Valley in summer and fall. A considerable number of favorable days had been discerned for the Sacramento area recently, when surface winds and, especially, winds below 2,000 ft. were studied. To extend the findings, spot climate recorders are to be installed in the northern part of the rice-growing areas, and nightly expeditions are planned into the same areas for upper wind observations. Under certain weather conditions these nightly winds have a high velocity in the Sacramento area at about 600 ft. height, a phenomenon called low-level jet, which acts as a "vacuum cleaner" for the city of Sacramento.

Meteorological equipment has been installed on the Sutter Buttes which permits distant wind monitoring at the 1,600-ft. level from the 2,000-ft. peak, using a 6-conductor cable of about 600-ft. length. The installation was finished by the end of May, together with a station on a lower knoll at about 700 ft. elevation. Both stations are equipped for continuous registering of upper wind conditions.

E. UP-GRADING RICE STRAW FOR ANIMAL FEEDING

Involvement of the Western Regional Research Laboratory in the disposal of lignified wastes results from longstanding interest in increasing the overall value of dehydrated alfalfa meal by separating it into leaf and stem fractions. It was reasoned that although the low-fiber leaf meal could find many feed outlets, the high-fiber stem material could be used only as ruminant feed. From an economic standpoint it seemed worthwhile to try to make the stein material as digestible as possible, for maximum benefits.

To evaluate the effect of different treatments on digestibility, a laboratory in vitro digestion method was developed for simulating digestion in the rumen. The new method uses commercially available enzymes. Results correlate extremely well with artificial rumen results with rumen fluid, and, more importantly, they seem to agree well with live animal tests.

In general, the digestibility of average untreated grass straw ran about 32%. This digestibility could be raised to 50%, with steam treatment and up to 70% with a steam and sodium hydroxide treatment. On 9 samples of grass straw, improvement in digestion ranged from 23 to 119% for steam alone, and from 55 to 183% for steam and sodium hydroxide together.

Comparable experiments were carried out on a single sample of rice straw. In vitro digestibility increased from 34% for untreated material to 43% for steam-treated product and 61% for steam-and-sodium-hydroxide treated product. The last figure compares very favorably with an average digestibility of about 55% for good alfalfa hay. These preliminary results indicate that treated rice straw may prove to be an excellent ruminant feed. Work is now in progress on interrelations between time, temperature, and alkali concentration, and their effects on digestibility and animal utilization.

 

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