Root Architecture in Relation to Nutrient Use Efficiency in Cassava (Manihot esculenta Crantz)

Tropical root crops constitute the subsidiary staple for about one fifth of the global population. Among these crops, cassava is the most important due to its higher biological efficiency, area under cultivation, acceptability as a secondary staple, ability to thrive under marginal environmental conditions, tolerance to pests and diseases, sustainability for continuous cultivation, quantity and quality starch for the preparation of value added products.

The experience from the long term fertilizer experiment still in progress at ICAR-CTCRI since 1977 reveals strong response of cassava to manures and fertilizers with an integrated approach involving organic manures, fertilizers and biofertilizers as the best. The concept of fertilizers being one of the culprits harming our health, resulted in evolving need based application of fertilizers based on soil nutrient status and crop requirement. However, the present scenario of fertilizer markets with respect to its price and availability at times of need are not that encouraging. Hence, nutrient use efficient (NUE) varieties which can explore soil nutrients from deeper soil layers due to its unique root system deserves special mention. They are an alternative in reducing chemical fertilizers as it can acquire nutrients from growth medium and can incorporate or utilize them in the production of root or shoot biomass or utilizable plant material.

At ICAR-CTCRI, the research work conducted for more than 10 years resulted in releasing the first K efficient cassava variety by name `Sree Pavithra` followed by identification of two N efficient genotypes W-19 and CR 43-8 and three NPK efficient genotypes CI-905, CI-906 and 7 III E3-5. The NUE is attributed to root architecture and leaf area index of the genotypes. Detailed root distribution studies of these genotypes indicated the presence of more of root hairs/white roots in these genotypes to devour the lower soil layers to absorb the unavailable water and nutrients.