Cassava (Manihot esculenta Crantz), popularly known as kamoteng kahoy, is often branded as “poor man’s crop” along with sweet potato, taro, and yam.
What once was an undervalued crop, cassava now stands as one of the staple food sources of carbohydrates in the country aside from rice and corn.
Protocols for site-specific nutrient management (SSNM) for cassava production paved the way for opportunities to maximize the crop’s potential in the country.
In 2016, nationwide SSNM trials wERE undertaken to further verify the said technology. It aims to address low yield and income among cassava farmers.
The Institute of Plant Breeding of the University of the Philippines Los Baños led and consolidated the findings across all the regions of the country.
NATIONWIDE SSNM TRIALS
Through the trials conducted, the efficiency of SSNM-based fertilizer recommendations was evaluated to address issues about the large yield gap between farmers’ yields and potential yields of different cassava varieties used in different cassava-growing areas.
It was found out that cassava responded to the use of fertilizer despite medium to high soil fertility.
However, cassava cultivation can deplete soil nutrients so non-usage of fertilizer will result in low yield. SSNM can compensate for such depletion by suggesting a set of management principles well-fitted to the growing environment.
In average, the amount of fertilizer needed to produce a ton of cassava dry root yield per hectare was 17 kilograms of N, 4.5 kilograms of P, and 27 kilograms of K.
Across all on-farm trials conducted, SSNM was found to be the most effective and efficient. However, it was not significantly different to the full NPK approach.
Forty-eight sites reported significant yield results during the second cropping season: 19 in Luzon, 14 in Visayas, and 15 in Mindanao.
Among the utilized varieties, Rayong 72 gave the highest yield for SSNM, reaching as much as 53.94 tons per hectare compared to Lakan 1, Lakan 2, and Golden Yellow varieties.
Rayong varieties have high yield potential as a feed type variety; hence, the highest fresh root yield.
Based on the data obtained through the nationwide trials, SSNM proved to be an efficient way to close the yield gap in the cassava production in the country. It can even help to close the yield gap mean of 10.53 tons per hectare.
Aside from the variety used, site characteristics have negative effects on cassava yield response to fertilizer management.
Optimization of SSNM can be made by adjusting the fertilizer recommendation based on the following factors: variety used, soil fertility, management practices (crop residue management, crop rotation, and organic nutrient inputs), climate, water availability, fertilizer source, and price.
SIGNIFICANT RESULTS OF TRIALS
Across all regions, fresh root yields for food type varieties ranged from 15.69 to 91.18 tons per hectare using SSNM protocols.
Zamboanga Peninsula region has the highest yield with an average yield of 91.8 tons per hectare. Varieties used in the region were Golden Yellow and Lakan 2 which are both food type varieties.
High yields were the result of expansion of areas. Newly cultivated sites have high indigenous soil nutrients to support cassava production.
Meanwhile, fresh root yields for feed type varieties produced 10.49 to 76.35 tons per hectare. Region 12 had the highest yield among all the regions with a yield of 76.35 tons per hectare using the Rayong 72 variety.
It was observed that regions in Mindanao have relatively higher yields in both food and feed type varieties compared to regions in Luzon and Visayas.
Generally, growing areas in Mindanao have fertile soils and experience evenly distributed rainfall very fitting for cassava cultivation.
For the comparison across varieties and locations, SSNM had the highest average yield among all treatments with 38.77 tons per hectare.
OPTIMIZING DATA FOR RECOMMENDATIONS
Data obtained from literature together with the results of the nationwide trials were utilized in developing the beta version of the Nutrient Expert for Cassava, a decision-support tool for generating SSNM-based fertilizer recommendations. At present, the validation trials being conducted is paving the way of a mature/refined Nutrient Expert for Cassava Philippines.
Once released, the software is hoped to give cassava farmers a fertilizer recommendation that can increase their yield and profit by suggesting a meaningful yield goal and providing a fertilizer management strategy. ### Jhon Marvin R. Surio
