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November 2015
Dit word algemeen gereken dat ‘n ketting net so sterk is soos
sy swakste skakel. Net so word die belangrikheid van S dikwels
onderskat en gevolglik word S dan die swakste skakel in die
voedingsketting. S-tekorte manifesteer byvoorbeeld by mielies as
‘n algehele geelverkleuring van die jonger blare, alhoewel die hele
plant soms geel kan vertoon.
Tydens ernstige S-tekorte kan die mielieplant ook verdwerg voor-
kom. Bogrondse groei word meer nadelig as wortelgroei geaffek-
teer. Foto 1 is ‘n voorbeeld van ‘n tipiese S-tekort vanuit The
International Plant Nutrition Institute se CD-ROM (2011).
Die nodigheid van grondmonsterneming (nie net die bogrond nie)
en die gebruik van grondontledingsdata vir bemestingsbesluite,
word versterk deur die feit dat Van Biljon et al. (2004) drempelwaar-
des vir mielies in die hoofproduserende gebiede van Suid-Afrika
vasgestel en gepubliseer het.
Vandag word hierdie norme in die Bemestingshandleiding van
die Fertilizer Association of Southern Africa (voorheen die Mis-
stofvereniging van Suid-Afrika) vervat. Hoekom dan die nodigheid
om norme deur navorsing vas te stel as S deur sommige as onbe-
nullig ten opsigte van mielieproduksie gereken word?
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1: S-tekort by ‘n mielie.
1