The effect of ratooning and planting density on stem and root yield quality of selected cassava (Manihot esculenta Crantz) varieties in Tanzania

Mushi, E.E.

The effect of ratooning and planting density on stem and root yield quality of selected cassava (Manihot esculenta Crantz) varieties in Tanzania

Autores

Descripción

Cassava (Manihot esculenta Crantz) is an important staple and food security crop in Sub-Saharan Africa. Approximately 850 million people living in the tropics depend on it as a source of carbohydrates and raw materials for industries. Despite its importance, the field management practices on stem production are significantly affected by cassava brown streak disease (CBSD) and Cassava Mosaic Disease (CMD) which pose a loss in quality and quantity of cassava root yield under fieldconditions. Management practices such as planting density have a significant impact on stem and root production. However, there is little information on how ratooning and planting density affect root yield and quality of different varieties of cassava growing in Tanzania where CBSD and CMD occurs. This study was designed to: (i) Assess the effect of ratooned cassava cuttings on root yield in the presence of cassava diseases (ii) Assess the effect of planting density on cassava stems and root yield of selected varieties. Commonly used methods in similar studies were used. The studied varieties were Mkuranga1, Kiroba, Chereko, Kizimbani and KBH2016B/521. On the effect of ratooning, significant differences were observed for foliar CBSD incidence at 3 months after planting 3 MAP (P<0.02), 6 MAP (P<0.001) and 9 MAP (P<0.001). Also significant differences were observed for total fresh root yield (TFRY) (P<0.02), marketable fresh root yield (MFRY) (P<0.001), harvest index (HI) (P<0.006), root necrosis incidence (RNI) (P<0.001) and root necrosis severity (RNS) (P<0.004) across ratooning cycles. For example: Kiroba was highly significantly affected by CMD at 6 MAP and 9 MAP. Similarly, stem cuttings from second ratoons of Kiroba were significantly affected by foliar CBSD at 6 MAP. Ratooned stems significantly affected the total fresh root yield (TFRY), marketable fresh root yield (MFRY) and root necrosis incidence (RNI). Root necrosis significantly affected the quality of the roots for second and third ratooned stems for all varieties except Kizimbani. For planting densities, the growth parameters such as the plant vigor and plant height (12 MAP) differed significantly among varieties (P<0.001). For yield parameters TFRY, MFRY, stem yield, and total biomass were significantly affected by varieties and planting densities (P<0.05). The interaction between varieties and planting density significantly affected the stem yield (P<0.001). The results from this study showed that ratooning affects the quality of planting materials especially second and third ratoon. All varieties except Kiroba were resistant to CMD. However, CBSD affected root quality in the second and third ratoon. Only Kizimbani does not seem to be significantly affected by root necrosis. In areas where CBSD is the major challenge, farmers should collect planting materials from unratooned and the first ratoon because are safer and have good qualities for root production. Planting density of (1 m x 0.5 m) produced the highest number of cuttings (Kiroba 319,944 cuttings/ha and KBH2016B/521 578,789 cuttings/ha) compared to (1 m x 1 m) (Kiroba 179,319 cuttings/ha and KBH2016B/521 276,581 cuttings/ha). Therefore, cassava seed producers are advised to use higher planting density as it produces the largest number of cuttings across all varieties.