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Fluid Journal : Fluid Journal 1996-1998
2 Fluid Journal Fall 1996 Implications When a dairy farmer commits to an intensive system, he has to get his pastures up to standard. Many southern pasture and hay crops are planted on soils that were unproductive for row crops. Soil and plant analyses often indicate a need for fertilization. This usually means higher than normal rates of P and K must be applied the first year or two to thicken stands, build strong root systems, and improve drought tolerance. Short-term in-season droughts are common in the South. Efficient moisture use is critical during these times. Studies have shown as much as a fivefold increase in yield when adequate fertilization was applied to grasses subjected to moisture stress. Potassium levels in common bermudagrass decline in the first year when there are three weeks or more between rains. Building soil test levels helps to avoid this problem. K concentrations should be maintained at 2 percent so milking cows can better tolerate sum-mer heat. This is extremely important at temperatures of 85°F and higher, and with high humidities. In addition, because grains and concentrates fed in the milking parlor are low in K, K concentrations in forages become even more important. Clipping bermudagrass (at 14-day intervals) can enhance nutrient recycling and help maintain high leaf- to-stem ratios. A drag or other implement behind mowers will help minimize "manure spots?' Use weekly forage analyses to monitor mineral concentration and deter-mine fertilizer applications. Applications of both P and K should be split, not applying all in the spring. Currently, dairy producers are split-applying 60 lbs/A of N plus other nutrients at 21-day intervals. Typical analyses contained N, P, K, plus 5, Mg, Zn and other micronutrients shown to be deficient in the weekly forage analyses. Total seasonal applications can exceed 2,400 lbs/A or more. Particular care should be taken to fit nutrient needs to the variety or hybrid being grown. Research has shown that new cultivars can vary significantly in yield and nutrient requirements. Useful tips Following are general guidelines that should be helpful in managing dairy pastures in the South for profitability: • soil test and monitor nutritional needs through plant analyses • balance NPK with secondary and micronutrients to optimize yield and quality • maintain adequate nutrition at all times • apply nutrients at short, uniform intervals to keep management simple and stabilize milk production • provide nutrition to fit specific cultivars being grown and use weekly forage analyses. Dr. Darst, PPI; Drs. Pratt, Pennington, Gass, Texas A & M University. Figure 2. Nitrogen fertilization has a dramatic impact on Coastal bermudagrass yields; Cooperative Extension Service, Univer- sity of Georgia, College of Figure 3. Nitrogen influence on protein and water-use efficiency of Coastal bermudagrass, Fisher and Caldwell, Texas Agricultural Experiment Station, Progress Report 2035. 100 N-lb/A 200 300 400 500 0 1 2 3 4 5 6 7 8 9 10 Yields - ton/A 0 N-lb/A 100 200 400 500 100 200 400 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 Protein - lbs/A Water-use - in/T 18 16 14 12 10 8 6 4 2 2 Protein Water-use
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