Reducing phosphorus inputs for grazing Holstein steers

A 2-yr study was conducted to confirm that managed pastures can provide Holstein steers adequate P to meet their daily requirement. Treatments offered were trace mineralized salt with or without additional P. In the first year, 80 Holstein steers (248 kg of BW) were assigned to 4 grazing groups. Treatments were trace mineralized salt only or a 67:33 mixture of trace mineralized salt and dicalcium phosphate. Steers rotationally grazed a cool-season grass/legume mixture for 137 d. Fecal bags were placed on 3 steers from each grazing group (n = 12) over a 4-d period for estimation of forage DMI and forage contribution to daily P intake twice during the grazing season. Analyzed pasture samples contained 3.28 mg of P/g of DM. During the second year, 72 Holstein steers (297 kg of BW) were blocked into 2 BW groups and subsequently assigned to 1 of 4 pasture groups. Steers rotationally grazed the same forage base as the first year for 126 d. Pasture samples contained 3.27 mg of P/g of DM. No significant differences (P > 0.10) were detected for BW, ADG, or free-choice supplemental mineral intake. Forage provided 126% of the recommended NRC P requirement. Thus, supplemental phosphorous was not required for Holstein steers grazing mixed, cool-season, grass/legume pastures.     

Effect of nitrification inhibitor on nutrient composition of winter wheat forage 1

Winter wheat (Triticum aestivum L.) is an important source of forage for cattle in the southern Plains. While high in quality, wheat pasture is prone to cause thousands of cattle deaths annually from nitrate poisoning, bloat, and wheat pasture poisoning, a syndrome of unknown cause. A large portion of the stocker cattle deaths on nitrogen fertilized pastures occur from unknown causes that appear to be related to forage composition. The objectives of this study were to determine seasonal trends in nutrient composition and to determine the effect of nitrapyrin, a nitrification inhibitor, on the change in nutrient composition of wheat forage over winter. The wheat was planted the last week of August on a Pullman clay loam soil (fine, mixed, thermic Torrertic Paleustol). Clip samples were collected periodically and analyzed for nutrient composition. Nitrogen, phosphorus, and potassium concentrations of the wheat forage varied during the season. Levels tended to be highest with the onset of growth and to decline as growth was decreased by cold weather. Nitrapyrin did not affect the concentration of any of the nutrients examined in the wheat forage. Concentration of nutrients, other than potassium, tended to be highly correlated with each other in both years of the study.     

Regression Analyses for Evaluating the Influence of Bacillus cereus on Alfalfa Yield Under Variable Disease Intensity

ABSTRACT We developed and tested regression methods to exploit the variability in disease inherent in field experiments, and applied the methods to evaluate strains of Bacillus cereus for biocontrol efficacy. Four B. cereus strains were tested for their effect on alfalfa (Medicago sativa) performance in 16 field trials planted during 1993 to 1996 at multiple sites in Wisconsin. To evaluate performance of the strains, we used the ratio of (metalaxyl response)/(untreated control response) as a measure of disease intensity within the experiments. The ratio of (Bacillus response)/(untreated control response) was then regressed as a function of disease intensity. The slope of the resulting line provides a statistical test to compare performance of the Bacillus strain with that of the untreated seed (H(o): slope = 0) and metalaxyl controls (H(o): slope = 1). Under conditions in which disease occurred, forage yield of plots planted with seed treated with B. cereus strain AS4-12 exceeded yield from the untreated control plots (P = 0.002) and was similar to yield of plots planted with metalaxyl-treated seed (P = 0.14). Yield gain associated with AS4-12 and metalaxyl seed treatment averaged 6.1 +/- 2.8% (+/-standard error) and 3.0 +/- 2.8%, respectively. In contrast to the regression approach, means analysis by analysis of variance did not detect differences among treatments. Three other B. cereus strains either did not increase alfalfa yield or increased yield less than did AS4-12. Metalaxyl and three of the Bacillus strains increased seedling emergence, but the improved stands were not predictive of increased forage yield. In six additional studies conducted for one season in 1997, AS4-12 enhanced yield of two cultivars at diverse locations in Wisconsin, but there was an apparent cultivar-location interaction. A strong correlation between response to AS4-12 and metalaxyl treatment suggests that these treatments controlled similar pathogens, most likely the oomycete pathogens Phytophthora medicaginis and Pythium spp.     

Digestibility and rate of passage by lambs of water-stressed alfalfa

Two lamb digestion experiments were conducted to evaluate the effect of alfalfa [Medicago sativa (L.)] grown under varying levels of water deficiency (stress) on the rate of passage and digestibility of various fibrous components. Experiment 1 consisted of a randomized complete block design in which 12 Suffolk X Hampshire crossbred wethers averaging 40 kg were fed alfalfa hay grown at three (10, 15 or 20 cm water/ha) levels of water per harvest. Experiment 2 consisted of a switchback design in which four Hampshire wethers averaging 45 kg were fed alfalfa hay grown at two (5 or 20 cm/ha) levels of water per harvest. Forage yields ranged from 1,420 (10 cm/ha in Exp. 1) to 4,200 (20 cm/ha in Exp. 2) kg/ha. In both experiments, water stress reduced cell wall constituents (neutral detergent fiber), acid detergent fiber, lignin and cellulose content of the alfalfa hay. Organic matter digestibility was decreased when the percentage of leaves fell below 60% at the highest yield. Digestibility of N and the rate of NDF digestibility were not affected by water stress. The second experiment additionally included nutrient balance and rate of passage measurements. Greater (P less than .10) amounts of N and P were absorbed from water-stressed than nonstressed hay. Ruminal retention time of particulate markers tended (P less than .10) to increase with greater water stress. The results of this study are interpreted to indicate that while moderate water stress may have little effect on in vivo digestibility of alfalfa, severe stress may reduce digestibility of fibrous fractions and total organic matter.     

Effect of nozzle type on runoff and yield of corn and sorghum under center pivot sprinkler systems

Summary Corn (Zea mays L.) and grain sorghum (Sorghum bicolor L.) production were compared under impact and spray nozzled center pivot sprinkler systems. The crops were grown under two pairs of sprinkler systems located approximately 110 km apart. One system of each pair was equipped with high pressure (379 or 414 kPa) impact sprinkler heads and the other system was equipped with low pressure (172 or 207 kPa) spray nozzles. Half of each circle was planted to corn and half was planted to sorghum. Additionally, four tillage treatments were included in the experimental design (conventional tillage, conventional tillage + deep ripping, conventional tillage + diking, and minimum tillage). The evaporative losses from the high pressure system with impact sprinkler heads were not significantly different from the low pressure system with spray nozzles. The minimum tillage and deep ripped treatments reduced runoff while diking eliminated it. The two nozzle types did not produce significantly different grain sorghum yields; however, corn yielded significantly more under the high pressure system with impact sprinkler heads than under the low pressure system with spray nozzles. The different tillage treatments did not influence yields of either crop significantly.Contribution of the Texas Agricultural Experiment Station. Paper No. 19198     

Effect of tillage and furrow irrigation timing on efficiency of preplant irrigation

Summary A field study to determine the efficiency of preplant irrigating with furrow irrigation and the effects of tillage and fall or spring application of preplant irrigation on this efficiency was conducted during 1983, 1984, and 1985 at the Texas Agricultural Experiment Station, North Plains Research Field at Etter, Texas on a Sherm, silty clay loam soil. Sorghum residue from the previous crop was shredded, gravimetric soil samples were taken, and five tillage treatments were imposed in the fall. The tillage treatments consisted of various combinations of disking, chiselling, moldboard plowing, and disk bedding. A preplant irrigation was applied in the fall to half of each tillage plot and in the spring to the other half of each plot. Soil samples were taken from each plot one month after the spring preplant irrigation. Sorghum (Sorghum bicolor L. cv. NC 178) was planted and irrigated similarly on all plots during the growing season. On the average, 237 mm of water were required to irrigate the tillage treatments during fall preplant irrigation and 466 mm were required during spring preplant irrigation. The additional water requirement in the spring was associated with increased water uptake by non-wheel-track furrows. Treatments with chiselling required larger water application during spring preplant irrigation. All treatments had similar soil water contents at planting time. Neither timing of preplant irrigation nor type of tillage had any effect on sorghum grain yield. Therefore, fall preplant irrigation was considerably more efficient than spring preplant irrigation. Averaged over the three years do study and five tillage treatments storage efficiency was 26% for fall application and 17% for springtime.Contribution of the Texas Agricultural Experiment Station, Paper No. 21724     

Grass Varieties for Horses

Many horse owners are concerned about sugar and fructosan levels in pastures and hay. While levels of these components have not changed in forages over the last century, the needs of horses have. Significant range in nonstructural carbohydrate contents of all grass species would allow for selection of varieties with lowered levels of these components. However, the grass seed industry must perceive a market for these types of grass before they would invest in the development of varieties and seed production and marketing of such types. Levels of these components currently vary with species, management, and the environment in which the plant is/has grown. Horse owners should be aware of these differences and use them to the benefit of their horses. Significantly lower levels of sugars and fructosans can be obtained by selecting grass species for low water soluble carbohydrate, then pastures can be managed or hay harvested with management practices favoring lowered nonfibrous carbohydrates. Forage can be analyzed for fructan or sugar, starch, and fructan can be estimated from nonfibrous carbohydrate analysis which is commonly determined in forage analysis.     

Half-sib family selection for forage yield in orchardgrass

Genetic variation for forage yield of orchardgrass is abundant, but there are few reports of progress from selection for increased forage yield. The objective of this study was to estimate direct effects of selection from one cycle of half‐sib family selection for forage yield in orchardgrass. Eleven selected populations were compared with their parent populations within three maturity groups. Populations were evaluated under hay management at three locations and management‐intensive rotational grazing at two locations. Nine of the 11 selected populations differed, by an average of 7.4%, from their parent population in forage yield. Nine of the selected populations also showed changes in Drechslera leafspot reaction, all indicating a negative genetic correlation with forage yield. Selection for high forage yield tended to result in greater ground cover and later relative maturity. However, changes in net herbage accumulation (NHA) under rotational grazing were generally not significant and were uncorrelated with changes in forage yield, indicating that forage yield of hay plots is not correlated with the NHA of grazed plots. Although genetic gains in forage yield measured under hay management were very favourable relative to other reports from the literature, the lack of correlated progress under grazing management indicates that directed selection for NHA of orchardgrass should be conducted under grazing management.     

Alfalfa (Medicago sativa L.) growth response to water and temperature

Summary Four cultivars of alfalfa (Medicago sativa L cv. Vangard, Cody, Zia, and Dawson) were grown under a gradient irrigation system on a Pullman clay loam soil (fine, mixed, thermic, Torrertic Paleustoll) at Bushland, Texas. Twelve harvests were taken during 1983, 1984 and 1985 over a wide range of irrigation levels. Alfalfa was harvested at 10% bloom and subsamples were oven dried and ashed. Irrigation water and rainfall were determined by catchment collections and soil moisture content was determined with a neutron soil moisture probe. Potential evaporation was determined by pan evaporation and by modified Penman, Priestley and Taylor, and Jensen and Haise prediction equations from climatic data. No varietal differences in the relationship of yield to water or water use efficiency occurred. Yield within each harvest correlated well with evapotranspiration (ET). The regression of yield with ET over all twelve harvests had a low coefficient of determination. Relative yield had a high correlation with relative ET when maximum ET was measured but the correlation was lower when maximum ET was calculated from a prediction equation or pan evaporation. The correlation increased when the maximum yield for each harvest was used rather than a constant value. Including a high temperature factor in the equation greatly improved the correlation between yield and ET but the correlation was not as high as when relative yield was correlated with relative measured ET. Water use efficiency was highest with the highest yields.Contribution Texas Agricultural Experiment Station. Paper No. 20929