EFFECTS OF MULCHING AND FERTILIZER SOURCES ON GROWTH AND YIELD OF ONION

Onion is an important horticultural vegetable in the urban Zimbabwe market. In Zimbabwe there is a need to improve the yield of onions on garden size areas utilizing locally available materials thereby avoiding purchased inputs which are often unavailable or inaccessible due to no supply or prohibitive price. The present study investigates the effects of trash grass and sawdust mulches in combination with organic and inorganic fertilizers on onion growth and yield. When the two mulching materials were compared, trash grass mulch favored the growth of onions more than sawdust mulch. Mulching improved soil water retention capacity, improved soil structure and suppressed weeds. These features played a significant role in the performance and ultimately the yield of onions. Similarly, total plant weight, aerial leaf weight, bulb weight and yields plot were also higher for samples taken from plots with trash grass mulch than those mulched with sawdust. This work also sought to evaluate mulching materials and fertilizer types on the various components of the onion plant at different stages of development and hence their contribution to the final yield. Trash grass in combination with organic and inorganic fertilizer the final yield improved by 160% and 310%, respectively. As for sawdust, final yield improved by 103% and 275% for combinations with organic and inorganic fertilizer respectively. The effect of fertilizer types alone on the growth and yield of onions was less dramatic than that of mulch.