Varietal improvement and agronomy research in Malaysia

Over the period 1994-1996, seven batches of seeds and two of meristem tissue cultures were evaluated and selected. As important as root yield is the trait starch content (or dry matter content) if a clone is to be accepted as a starch cultivar. At the time of reporting a number of clones have been identified as having yield levels similar to the high-yielding early cultivar MM 92, while showing dry matter contents equivalent to that of the commercial starch cultivar Black Twig. Two of these promising clones have also been evaluated positively for processing into oil fried crisps, a popular local snack.

Agronomic research included various studies on nutrient inputs and the effects of flooding on cassava performance when the crop is planted on drained peat. With the early cultivar MM 92, fertilizer inputs may be halved and applied once every alternate cropping without affecting root yields. While the effect of Ca application was not clear-cut, there was some indication that Ca applied as a 9 % foliar solution of Ca(NO3)2 or as 1 ,500 kg/ha of CaCO3 to the soil improved root dry matter content. Solid wastes from starch processing factories may be returned to the soil at the rate of 1.0-1.5 t/ha as a supplement to chemical fertilizer inputs. MM 92, in contrast to 12- month Black Twig (critical stage at 3 1/2 months), showed the greatest yield reduction when flooding occurred at 4-5 months after planting. Four days of continuous flooding resulted in yields declining as much as 45%.