Effects Of Weed Density And Species Diversity On Cassava (Manihot Esculenta Crantz) Yield In Zambia

ABSTRACT

Cassava (Manihot esculenta Crantz) is one of the important crops in the world for food

and income security. Cassava production is challenged by weeds as they reduce yield to

100%. Effective weed management in cassava production depend determination of weed

species diversity and determination of Critical Period for Weed Removal (CPWR). A

study was conducted in Zambia, to document weed species diversity in cassava growing

areas of Chongwe and Kaoma districts in Zambia, determine the critical period for weed

removal in three cassava varieties (Nalumino, Mweru and Chila) commonly grown and

estimate yield losses caused by weeds on cassava farms in the two districts. Farmer survey

was done to get farmers experience in weed management. The experiment was established

whereby, two weeding regimes were applied; weed free (WF) and weed infested (WI).

Sampling of weeds for density, species diversity and yield components was done within

the period of 21 days until 168 Days After Planting (DAP). Weed species diversity index

in Kaoma was 2.12 and Chongwe was 3.487 (Shannon diversity index) Forty weed

species in Chongwe and 33 in Kaoma were identified. Findings reveal that CPWR was

between 42 and 105DAP. Cassava root yield 6 months after planting in weed free plots

was significantly higher than in weed infested treatments. All varieties were affected by

weeds, and under un controlled weed condition the loss of 99.9% was recorded.

Therefore, keeping the crop weed free during the first four months of growth is important

for all varieties in order to reduce significant yield penalty. Additionally, further studies on

weed seed bank and herbicide screening is important to postulate appropriate weed

management and reduce drudgery respectively.

Key words: critical period for weed removal, weed management; weeds in cassava,

cassava yield loss, weed species diversity.