Soil Fertility and Liming Practices for Production of Annual Ryegrass
- Vincent A. Haby and
- D. L. Robinson
Annual ryegrass (Lolium multiflorum Lam.) is a high-quality, cool-season forage that responds to soil fertility levels under varying soil, climatic, and management conditions. On high clay-content, tilled soils, N rates up to 448 kg ha−1 applied in increments of 112 kg ha−1 have maintained forage production more uniformly throughout the growing season than a single N application. In a dual-cropping system with bermudagrass [Cynodon dactylon (L.) Pers.], annual ryegrass is seeded later in the fall and has a lower yield potential. Under these conditions, N applied after seedling emergence and again in December, February, and April at rates approximating 70 kg ha−1 at each application has optimized ryegrass production. Rycgrass responds to limestone treatment of acid soils where surface 0- to 15-cm soil pH approximates 5.1 (1:2 soil/water) or lower. Aluminum solubilizes rapidly below pH 5.5 and can be toxic to ryegrass. Acid soils should be limed to maintain pH above 5.5 for production of annual ryegrass and to maintain nutrient use efficiency, especially P use because soil Al and hydroxyaluminum compounds complex this nutrient. The optimum rate of P for maximum ryegrass production in deficient soils is expected to increase as N rates are increased under high yield conditions. Ryegrass increases uptake of K as applied K rates are raised. At 90% of maximum yield, ryegrass removed 180 kg of K ha−1, or 18 kg t−1 of dry forage. Estimates indicate that <2% of the K in forages consumed by cattle in a continuous grazing system is transferred from the pasture as animal tissue K. In alkaline soils, Ca is usually adequate, but is applied as limestone to acid soils. The Ca needs of most classes of cattle can be obtained from annual ryegrass grown on acid soils limed to maintain pH near 6.0. Ryegrass contains lower levels of Mg in late fall and winter, particularly after cold, wet periods and in young regrowth tissue. Concentrations of Mg below 2.0 g kg−1 may cause hypomagnesemic tetany in beef cows during initial stages of lactation. Aluminum depresses Mg uptake while increased plant uptake of P enhances Mg uptake by ryegrass. The soil test for S deficiency levels has generally been inadequate to predict ryegrass response to this nutrient. Ryegrass response to applied S has usually been greatest at high N application rates on sandy, low-organic-matter soils. Ninety percent of maximum ryegrass yield has occurred at a S concentration of 1.2 g kg−1 or at a N/S ratio of 20 in the youngest open leaf.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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