Systems for sustainability of alfalfa production on acid, Coastal Plain soils using various harvesting strategies
Sustainability of alfalfa production on four ranch sites was continued in 2002, the third production year for these sites. Beef cattle grazing trials for evaluation of six grazing-tolerant alfalfa varieties and for comparison of cattle weight gains grazing alfalfa versus common bermudagrass have been completed and data are being compiled for reporting and publication. Analysis of alfalfa plant samples for hexose and other enzymes in samples collected from field and greenhouse trials on the effectiveness of treatments for reduction of phytotoxic levels of subsoil aluminum was continued. Soil sample collection and analysis from these field sites was also continued.
1.) Development of soil amendment and nutrient management plans to enhance establishment and sustainability of alfalfa on acid, Coastal Plain soils.
2.) Develop multiple-option defoliation strategies using hay, silage, greenchop, and/or grazing to improve stand survival and sustainability of alfalfa.
3.) Develop risk assessment models to project economic benefits from alfalfa production on Coastal Plain soils.
4.) Use a variety of the latest technologies to transfer best management practices to stakeholders in the southern US.
1. Subsoil aluminum detoxification studies.
Field studies at Overton and Nacogdoches, Texas and a greenhouse experiment at Overton were established to evaluate the effectiveness of gypsum and calcium sulfite, a flue gas desulfurization by-product, for reducing phytotoxic subsoil aluminum levels in strongly acid soils. Alfalfa was harvested for yield by treatment and replication at both locations during the 2002 growing season. Yield data and samples for chemical analysis were collected. Analyses have been completed on plant samples collected from these sites. Soil samples were taken at both the Rusk and Nacogdoches County sites in late-winter 2003 to 48-inches deep and separated at 0-6, 6-12, 12-24, 24-36, and 36-48 inches. Analyses have been completed on the Nacogdoches County samples. Analysis of Rusk County samples is currently in process. Data will be evaluated to determine if surface treatments applied in 1999 are affecting sub-surface properties. Preliminary analysis of data from samples collected in 2000 indicated no treatment differences for subsurface pH or soluble aluminum levels. Statistical analysis of these data currently is in process.
2. Organic analyses of alfalfa from amendment experiments.
Organic analyses of alfalfa samples collected (frozen in liquid nitrogen at sampling) from aluminum detoxification studies in the greenhouse and field is continuing. In the field studies at Nacogdoches, the sludge treatments induced higher hexose content then the gypsum treatments. In alfalfa from harvests one and two, the sludge and gypsum amendments lowered the hexose contents compared to the control alfalfa, but in harvests three and four, the hexose contents were higher than in the control alfalfa. However, the hexose contents of alfalfa from harvests one and two were higher than in harvests three and four. The effects of the soil amendment on the alfalfa total protein content were opposite to the effects on the hexose because harvests three and four protein contents were higher than those of harvests one and two. The protein contents of harvest 2 were as much as 58% lower than those of harvest 1. The sledge treatments lowered the alfalfa total protein content compared to the control plot alfalfa, while the gypsum treatments did not change the protein contents.
In the Overton field experiments, the 4th harvest had as much as 100% more hexose then the 2nd harvest. In general, the 3rd and 4th alfalfa harvest had higher hexose content then the 1st and the 2nd harvests both in the treated and control alfalfa. The converse was the case in the Nacogdoches experiments. The sludge and gypsum were detrimental at Overton because they decreased the hexose contents in alfalfa compared to the control. The effects of the soil amendments on total protein contents were better than on the hexose because the sludge treatments increased the protein contents of the 1st harvest. Therefore, the antagonistic effects of the amendments on the alfalfa protein and hexose contents prevented the selection of the best amendments for the soil.
In the greenhouse experiments on aluminum detoxification at Overton, gypsum treatment in the absence of applied boron decreased the alfalfa total protein but increased the hexose content. Boron at 1.5 kg per hectare without gypsum increased the hexose level approximately 15%, but addition of gypsum decreased the hexose level. The 1.5 kg of boron decreased the total protein with or without gypsum treatment. Boron at 3 kg per hectare together with 5 tons of gypsum per hectare decreased the alfalfa total protein level, but together with 10 tons of gypsum, it increased the protein by about 4% compared with the control (without boron and gypsum). Boron at 4.5 kg per hectare together with 5 tons of gypsum did not affect the alfalfa protein level, but with 10 tons of gypsum, it induced a 14% decrease in the protein level. Therefore, boron and gypsum exerted antagonistic effects on the protein and carbohydrate metabolism similar to the effects of sludge and gypsum.
All the soil amendments induced some limited improvement on the alfalfa metabolism, but because of the antagonistic effects of calcium, aluminum, and boron on alfalfa metabolism, the hexose and protein contents were not adequate indexes for selection of the best amendment for the soil.
3. Grazing tolerance of alfalfa varieties.
The six alfalfa varieties that were established in six replications for evaluation of stand maintenance and sustainability included Alfagraze, GrazeKing, Amerigraze 401+Z, Hay Grazer, Amerigraze 702, and Cimmaron 3 I. Grazing was initiated in spring of 1999 and continued through 2001 during the spring-summer using the following stocking treatments: (1) Continuous stocking with grazing to a height of 3-inches or more; (2) rotational stocking, initiate grazing at Stage 5 or 10% bloom and graze to three-inch stubble; (3) rotational stocking, initiate grazing at Stage 3 or pre-bud and graze to a three-inch stubble. The duration of stocking on rotational treatments was three days or less. Testers were stocked March through September. In November 2001, final plot readings for plant count, stems per plant, stand height, and percent stand were conducted.
Except for a few isolated plants, Alfalfa was not sustainable in plots that had been continuously stocked. The grazing treatment of rotationally stocking as plants reached Stage 3 resulted in nearly complete loss of stand in one block of three replications, and about 50 to 100% loss of stand in the other block of 3 replications. The only grazing treatment that had substantial, sustainable alfalfa stand was the rotational stocking when plants reached Stage 5 or about 10% bloom. The most detrimental factors contributing to significant stand lost during this grazing experiment were summer drought and the invasion of common bermudagrass. By nature of the graze-deferred treatment of rotational stocking when plants reached Stage 5, the alfalfa canopy reduced the extent of plot invasion by bermudagrass.
During the spring of 2002, surviving alfalfa plants and plots were identified for potential use in plant breeding programs. Drought-like conditions during mid-summer enhanced mortality of plants. Due to the severe alfalfa stand lost in all plots, there was no additional collection of plants or data recorded. The entire plot area was reclaimed for additional experimentation using appropriate herbicide applications.
The rotational stocking and utilization strategies of stocking rate are not compatible with sustained alfalfa production under grazing in East Texas. Thus, a major accomplishment of this experiment has led to conclusions that alfalfa is not sustainable, grazing forage for the Coastal Plain soils of East Texas in which summer drought frequently and normally occurs. Other selected plot experiments showed good to moderate sustainability when grazing was not the predominant method of forage harvest.
The primary impacts of this experiment on southern producers was that alfalfa may be best suited primarily as a hay crop with intermittent grazing during the early spring and late fall. In addition, the management required for successful stand maintenance of alfalfa in this environment may be more suited to intermittent grazing by dairy and/or hay production rather than season-long grazing by beef cattle.
4. Grazing comparisons with alfalfa and common bermudagrass
A replicated study was established at Hope, Arkansas to evaluate beef cattle performance on grazed alfalfa compared to grazed common bermudagrass. The field data collection planned for this trial was completed in fall 2001. Two years of animal performance data have been collected and preliminary analysis is completed. A graduate student has begun laboratory forage nutritive value analysis of samples collected during the trial and will also conduct an economic evaluation of the grazing comparison data collected. Grazing comparison data planned for collection into 2002 were not made because the project leader moved to another location and the alfalfa was sprayed to remove it so the field could be prepared for other research.
Observations and some preliminary conclusions from this study at Hope, Arkansas are as follows: Stocker calves having free access to a bloat preventive showed no signs of bloat at any time while grazing alfalfa. Grazing alfalfa required greater attention to management than grazing bermudagrass without large improvements in grazer performance. Aggressive summer weeds and herbicides applied to control these weeds required grazing withdrawal periods that are incompatible with timely grazing. A similar situation occurs with insects and insecticide applications. Periods of high rainfall that necessitated pulling cattle off alfalfa to avoid trampling damage interfered with timely grazing and damaged alfalfa in low spots that became waterlogged for extended periods. Alfalfa reached flower stage rapidly during hot summer weather and often before pesticide withdrawal periods were over. Stocker calves did not effectively grazed alfalfa once it passed the late bud growth stage, leading to poor utilization of the standing crop with resultant poor calf performance, especially in summer. Alfalfa went dormant during summer drought. Some of these problems incurred with grazing could be eliminated if alfalfa were grown by producers who have the capability to harvest the crop as hay when it outgrows the ability of grazers to consume it. Also, adult cattle would probably utilize the mature alfalfa stands more effectively than stocker calves in the summer.
5. Alfalfa sustainability studies with stakeholders.
Alfalfa production demonstrations with stakeholder ranchers were maintained and harvested in 2002. Sites located in Gregg, Cherokee, Anderson, and Smith Counties in Texas were treated with best management practices that we have developed for alfalfa production on Coastal Plain soils. Yield estimates were made from meter-square quadrant samples before each harvest. Yields in 2002 ranged from 5.34 to 1.66 tons of 12%-moisture hay/acre depending on management.
Alfalfa yield was highest at the Seven-P ranch. No major problems were experienced on this site during the 2002 growing season. Harvesting operations were conducted in a timely manner. The estimated economic return on this site was the highest of these four sites. The Taylor ranch site had the next highest yield with the economic return similar to the Seven-P ranch. Yields on this site appeared to be declining due to invasion of common bermudagrass into the alfalfa stand. Yields on the Griffin ranch are about 0.5 tons lower than at the Taylor ranch. At the Griffin ranch, regrowth following the third cutting was affected by drought, grasshoppers, and extensive grazing by the resident native whitetail deer population, so there was not a fourth cutting. Invasion of common bermudagrass is increasing at this site and additional spraying for pest control was needed, so the economic return was decreased. Estimated hay yields on the Riley ranch were much lower than at other locations. At this site, harvest delays due to extended grazing periods reduced the number of regrowth cycles from which to estimate yields, and the economic return based on hay yield indicates that this site lost money. Weight gains of livestock grazing alfalfa on this site were not determined for economic evaluation; therefore the net economic return is misleading. At the end of the third production year and this granting period, stands of alfalfa on each of these ranches are adequate to continue production and economic evaluation for another season.
Crude protein content ranged from 21.6 to 19.5 % on the Griffin Ranch, 24.3 to 18.6 % on the Taylor Ranch, 23.5 to 14% on the 7-P Ranch, and from 24.6 to 15.7 % on the Riley Ranch. The highest level of crude protein occurred in the first cutting and generally declined in successive cuttings into late summer. Concentrations of phosphorus and potassium in the alfalfa remained relatively similar to the averages presented in Table 2 throughout the season.
Impacts and Contributions/Outcomes
Results from this research and demonstration project offer producers high-quality alternative forage for production on carefully selected soils on farms and ranches in the Southern Region. Grazing alfalfa in this region may not be as attractive of an alternative as is alfalfa planted for hay production. Environmental problems such as excessive rainfall or prolonged drought and layout periods required due to chemical applications for pest control interfered with effective grazing management in grazing trial comparisons. In the variety sustainability grazing trials, alfalfa stand reductions due to continuous grazing and to rotational grazing before the 10-percent bloom stage of growth were shown particularly harmful to alfalfa stands. Intensive grazing of first growth alfalfa during a time when environmental conditions are not conducive to hay production and grazing of final growth alfalfa following a hard freeze may be the best grazing alternatives for this region.
Economic analysis of hay yields from demonstration sites projected that net income ranged to $208 per acre during the third year of production when hay was valued at $135 per ton. Income in this range exceeds that from most other forages produced in the Southern Region, and can be used to greatly improve the standard of living of farmers, ranchers, and local and regional communities. We are continuing on-farm alfalfa stand sustainability into the fourth year in 2003.