The responses of tall fescue and white clover to lime and phosphorus on highly leached soils of the natal mistbelt

Abstract

The influence of lime and P on the performances of pure white clover and white clover/tall fescue swards on two highly leached Mistbelt soils was examined in factorial design. First season data, discussed in this paper, indicated highly significant dry matter responses to both lime and P. The pattern of response to P. varied over the three harvests obtained in the season and a single optimum P level was not manifested for either clover or fescue. Decreases in extractable (0,05 NH₂SO₄) P levels with increasing lime rates were noted on both soils. Clover yield responses to lime were coincident with the reduction of soil acid saturations to below 18 percent. Fescue yield increased linearly with liming rate to the highest lime level applied (20,4 tonnes/ha); this response is thought to be partly attributable to the influence of lime on N mineralisation from soil organic matter.

Uittreksel

Die invloed van kalk en fosfor op die prestasie van suiwer witklawer en witklawer/langswenkgras weidings op hoogs geloogde Misbelt gronde is deur middel van ‘n faktoriale ontwerp ondersoek. Die eerste seisoen se data toon ‘n hoogs betekenisvolle reaksie van droë materiaal op beide kalk en fosfor aan. Die patroon van die reaksie op fosfor het oor die drie oeste van die seisoen gevarieeren ‘n enkele optimum fosfor peil is nie by of witklawer of langswenkgras waargeneem nie. ‘n Verlaging in ekstraheerbare (0,05N H₂SO₄) fosfor met verhoogde kalk toediening is by albei grondsoorte waargeneem. Die reaksie van witklawer op kalk toedienings was in ooreenstemming met ‘n verlaging in die suurversadiging van die grond tot onder 18 persent. Die opbrengste van langswenkgras het met kalk toedienings tot by die hoogste peil (20,4 tonne/ha ) lineêr toegeneem: hierdie toename is moontlik gedeeltelik toe te skrywe aan die invloed van kalk op stikstof mineralisasie van grond organiese materiaal