Haby, Vincent A.

Kerby, Joel L.

Nimr, Gary H.

Rouquette, F. M., Jr.

Silveira, M. L.

English

Texas A&amp;M Repository

    PUBLICATIONS 2006 SOIL DEPTH DISTRIBUTION OF POTASSIUM IN COMMON AND COASTALBERMUDAGRASS PASTURES UNDER 30 YEARS OF GRAZING AT DIFFERENTSTOCKING RATESM.L. Silveira, F.M. Rouquette, Jr., J.L. Kerby, G.H. Nimr, V.A. Haby, and G.R. SmithBackground. A detailed description of stocking rates and fertility regimens from 1969through 2005 are presented in a companion 2006 Field Day Report by Rouquette et al. Theobjective of this study was to evaluate changes in soil potassium (K) distribution in bermudagrasspastures under different stocking rates and fertility regimens.Research Findings. Soil K concentrations in lower soil depths were slightly increasedfrom 1975 to 2004, especially on Coastal bermudagrass pastures (Figure 1). This patternsuggested that K has accumulated at low concentrations in the soil in response to continuousstocking and applications of potash (- 0-0-62) fertilizer. Common bermudagrass pasturesreceiving K fertilizer, overseeded with clover, and stocked at a high stocking rate unexpectedlyshowed the lowest K concentration among the treatments. Low stocked common bermudagrasspastures (no N +K +Clover) showed greater soil K concentrations than pastures receivingN+K+ryegrass pastures. At high stocking rates, however, no clear effect of overseeding with K+c1over versus N +ryegrass was observed. This indicated that bermudagrass pastures fertilizedwith N, overseeded with ryegrass and receiving no K fertilization for more than 13 years (1985-1997) can exhibit relatively similar soil K concentrations to those in pastures annually fertilizedwith K and overseeded with clovers. From 1998 through 2004, all pastures received equalamounts of KzO (Rouquette et al). Clover has much greater requirements for K than doesryegrass.Soil K concentrations, in general, ranked between very low (0-90 ppm) to low (91-130ppm) levels. Relatively greater K levels (above 130 ppm) were observed in deep horizons (24-80") on Coastal bermudagrass pastures sampled in 2004. Although soil test indicated that Klevels were low for optimal bermudagrass growth, no forage stand losses were observed. Therewas no significant effect of stocking rates on K distribution in soil. Nutrient cycling via animalexcreta and plant recycling is presumably supplying adequate amounts of K to sustainbermudagrass stands.Applications. Coastal Plain soils can exhibit very low available K levels. Annualfertilization seemed to have little effect on soil K concentrations in bermudagrass pastures.Nutrient cycling in grazing system was an important pathway to re-supply K to the soil andmaintain forage stands for more than 19 years. From an economic and agronomic perspective, K49fertilization rates based on soil test levels should be carefully examined in bermudagrass pasturesunder continuous stocking, In contrast, bermudagrass that is used primarily for hay will requireannual applications of K, and on Coastal Plain soils these N-P20S-K20 ratios may range from 5-1-5 to 4-1-3.Common Bermudagrassa. High Stocking Rate b. Low Stocking RateK (ppm)80 120 160 20040o6of---t~"O'...........- ...._ ....._ .....667818g 30.r:.Q. 42Ql'tJ'0 54UJ160 200K (ppm)80 12040o6 +'111,........*_:>--.....---11.00-_...187866g 30.;g. 42'tJ'0 54UJCoastal Bermudagrassa. High Stocking Rate b. Low Stocking RateK (ppm) K (ppm)0 40 80 120 160 200 0 40 80 120 160 2006 618 18"2 30 - 30- g;; 42 .; 42Q. Q.Ql Ql'tJ 54 'tJ 54'0 '066UJ 66 UJ78 7890 90o 1975 A 2004 (no N +K +Clover) • 2004 (N +K +Ryegrass)Figure I. Soil K distribution with depth in common and Coastal bermudagrass pastures underlong-term stocking and varying fertility management.50

Soil Depth Distribution of Potassium in Common and Coastal Bermudagrass Pastures Under 30 Years of Grazing at Different Stocking Rates

https://oaktrust.library.tamu.edu/bitstream/1969.1/189692/1/article30.pdf

Soil Depth Distribution of Potassium in Common and Coastal Bermudagrass Pastures Under 30 Years of Grazing at Different Stocking Rates

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Texas A&M Repository

Soil Depth Distribution of Potassium in Common and Coastal Bermudagrass Pastures Under 30 Years of Grazing at Different Stocking Rates

Abstract

Similar works

Full text

Available Versions

Texas A&amp;M Repository

Texas A&M Repository