Long term nitrogen and phosphorus application to veld

Abstract

The long term effects of a 5N x 3P factorial fertilizer application trial on hay yields, botanical composition and soil properties of veld are presented. Significant increases in hay yields were recorded during most years. There was a strong correlation (r = 0,757) between mean (over all 15 treatment combinations) annual hay yields and annual rainfall.

N and N + P fertilizer lowered the percentage basal cover of the tribe Andropogoneae. A notable exception of this tribe was Heteropogon contortus which increased significantly at the lower fertilizer levels. The basal cover of the tribe Paniceae generally increased with N and P fertilizer application. The reaction of the basal cover of the tribe Eragrosteae showed little by way of definite tendencies.

Increasing N and P levels generally resulted in decreases in soil pH, Ca, Mg, K and an increase in compaction of the soil surface layer. However, higher levels of N x P resulted in higher water infiltration rates than occurred in control plots, although initial infiltration rates were greatest in control plots. Despite certain undesirable effects of fertilizers on basal cover and certain chemical and physical properties of the soil, the fertilized plots maintained a high level of production.

Uittreksel

Die langtermyn uitwerking van ‘n SN x 3P faktoriaal bemestingsproef op hooi opbrengs, botaniese samestelling en grondeienskappe van veld word aangetoon. ‘n Betekenisvolle verhoging in hooi opbrengs kon oor die meeste jare verkry word. Daar was ‘n sterk korrelasie (r = 0,757) tussen jaarlikse reënval en gemiddelde (oor al 15 behandeling kombinasies) jaarlikse hooi opbrengs.

N en N + P bemesting het die persentasie basale bedekking van die tribus Andropogoneae verlaag. Die bedekking van die tribus Paniceae het oor die algemeen toegeneem met N en P bemestings toedienings. Die reaksie van die basale bedekking van die tribus Eragrosteae het min duidelike neigings getoon. ‘n Toename in N en P peile het oor die algemeen ‘n afname in grand pH, Ca, Mg, K en ‘n toename in verdigting in die boonste grondlae veroorsaak. Hoër peile van N x P het egter ‘n verhoging in infiltrasietempo veroorsaak teenoor die kontrolepersele alhoewel die aanvanklike infiltrasietempo die hoogste was in die kontrolepersele. Ten spyte van sekere ongewenste gevolge van bemesting op basale bedekking en sekere fisisiese en chemiese eienskappe van die grond, het die bemeste persele ‘n hoë peil van produksie kon handhaaf.

Additional index words:

• Ammonium sulphate
• botanical composition
• hay yield
• soil characteristics
• super phosphate

Notes

New address ‐ Dept. of Agriculture (Karroo Region) Private Bag X529, Middleburg, 5900