Potassium competition in a kudzu-merker grass association

Abstract

Examination of a competition for potassium in a kudzu-Merker grass association on Fajardo clay at Río Piedras showed: There were no significant responses in yields to the application of potash, magnesium oxide, or borax by either kudzu or a kudzu-Merker grass mixture for two cuttings. The highest gain in yield was obtained when potash was applied to the kudzu-Merker grass association. A chlorosis of the kudzu evidenced by a yellowing of the older leaves with marginal leaf-burning was found on all plots not receiving potash. This chlorosis was more severe during the drier weather than in the rainy season. Leaf analysis of the kudzu and Merker grass at harvesttime revealed no appreciable difference in protein, nitrogen, or phosphorus contents attributable to any of the treatments. Potassium values were all lower for the kudzu grown with Merker grass than for that grown alone. Samples of chlorotic kudzu leaves taken before harvest contained less potassium than normal kudzu leaves taken from the same plots. Evidence is presented of the competition for potassium by grasses and legumes as was found by other workers. The authors also discuss the importance of this competition in establishing legumes in grass-legume mixtures for soils low in available potash in Puerto Rico.