Residual Nitrogen Effects on Soil, Forage, and Steer Gain

William A Berg,Phillip L Sims

doi:10.2307/4003280

Abstract

Nitrogen fertilization is a common practice on introduced grass pastures established on marginal farmland in the Southern Great Plains. The efficiency of N fertilizer use on pastures and concern about nitrate movement into substrata prompted this study of residual N effects following fertilization. The study was conducted on Old World bluestem (Bothriochloa ischaemum L.) pastures on Pratt soil (sandy, mixed thermic Psammentic Haplustalfs) in western Oklahoma where the 57-year average annual precipitation is 566 mm yr(-1). Herbage production and steer gains were quantified over 3 summer grazing seasons on paddocks fertilized annually with 0, 34, 68, or 102 kg N ha(-1) yr(-1) during the preceding 5 years. Peak standing ungrazed herbage yields were 2- to 4-fold greater in paddocks fertilized the preceding 5 years and were linearly related to the total N applied the previous 5 years. Steer weight gain responded linearly to N with an average of 0.63 kg gain over 3 years per kg N applied over the preceding 5 years. No differences (P > 0.05) in soil nitrate concentrations to a depth of 2.8 m were measured among the N rate treatments. Overall, substantial effects of residual N were measured in both herbage mass and steer weight gain for 3 years following 5 years of N fertilization. DOI:10.2458/azu_jrm_v53i2_berg

Highlights

IntroductionNitrogen (N) fertilization of introduced grass pastures is a common practice in western Oklahoma and adjacent areas in Texas (Dahl and Cotter 1984, Berg and Sims 1995)
Nitrogen fertilization is a common practice on introduced grass pastures established on marginal farmland in the Southern Great Plains
Nitrogen (N) fertilization of introduced grass pastures is a common practice in western Oklahoma and adjacent areas in Texas (Dahl and Cotter 1984, Berg and Sims 1995)

Summary

Introduction

Nitrogen (N) fertilization of introduced grass pastures is a common practice in western Oklahoma and adjacent areas in Texas (Dahl and Cotter 1984, Berg and Sims 1995). These pastures are usually established on marginal farmland that are deficient in plant-available N as a result of up to 100 years of cultivation and subsequent erosion (Haas et al 1957). A single application of 68 kg N ha-1 yr-1 in April to WW Spar Old World bluestem (Bothriochloa ischaemum L.) pastures in western Oklahoma generally resulted in maximum forage mass and steer weight gain (Berg and Sims 1995).

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Conclusion