Effect of Harvest Time and Nitrogen Doses on Cassava Root Yield and Quality

Abstract

ABSTRACT:Nitrogen is considered the most limiting nutrient for cassava, and N availability can influence the crop cycle, including earlier harvest. The aim of this study was to study the effect of harvest time on the production components of cassava, "Aciolina" cultivar, at different rates of N fertiliser. The experiment was carried out in an area newly incorporated into the productive system in a savannah ecosystem in the northern Amazon. A randomised block experimental design was used in a split plot arrangement with four replications. The N rates (0, 30, 60, 150, and 330 kg ha -1 ) were allocated to the main plots, and the harvest times (90, 120, 150, 180, 240, 300, and 360 days after emergence of the stalks -DAE) were allocated to the subplots. Plant height, shoot fresh matter yield, number of roots per plant, average root diameter, and root fresh matter yield display an increasing linear response up to 360 DAE in cassava cv. "Aciolina". For all harvest times, the N rates promote an increase in root fresh matter yield. At 300 and 360 DAE, the root fresh matter and starch yield and the harvest index show a quadratic response as a function of the N level. The greatest efficiency of N topdressing on the production of root fresh matter occurs at 300 DAE, promoting an earlier harvest. At that time, the dose of maximum technical efficiency, 226 kg ha -1 N, results in a yield of 62 Mg ha -1 of root fresh matter, 13 Mg ha -1 of starch, and a harvest index of 81 %.

Leaf area development and yield of cassava in response to pruning of shoots and the late supply of nitrogen and potassium

“…Our results showed that a higher LA at the beginning of the second vegetative cycle of cassava (between 4 and 8 mo after shoot pruning) is also a determining factor for the yield of cassava storage roots, starch, and flour (Table 6). Several studies have shown that cassava yield responds positively to N fertilization during the first vegetative cycle (Kaweewong et al., 2013; Oliveira et al., 2017; Sangakkara & Wijesinghe, 2014; Viana et al., 2005), but our results showed that the late N supply also improves cassava yield.…”

“…The plants pruned during the autumn–winter resting phase could not grow to the same height or produce as many leaves as the unpruned plants, even 8 mo after shoot pruning, regardless of the K supply. The application of N during the first vegetative cycle usually increases the height of cassava plants (Oliveira et al., 2017; Thummanatsakun & Yampracha, 2018; Uwah et al., 2013; Viana et al., 2005), but our results showed that the supply of N during the second vegetative cycle of cassava also increased the height of the plants in the dry season planting.…”

“…However, 4 mo later (at the second evaluation), the number of leaves per plant increased with N fertilization regardless of the shoot pruning–K management approach adopted (Figure 3b). According to other authors, N increases the overall growth of cassava plants (Howeler, 2002; Kaweewong et al., 2013), the fresh biomass of shoots (Oliveira et al., 2017), and the LAI of plants (Howeler, 2002; Kaweewong et al., 2013). However, shoot pruning or the supply of K did not intensify the effect of N fertilization on LA reconstitution, but it was evident that N fertilization provides greater restoration of the LA and LAI of cassava plants during the second vegetative cycle (Figure 3).…”

“…According to Oliveira et al. (2017), higher N application rates during the first vegetative cycle of cassava increase the number of roots per plant, but differences in the number of roots of plants grown with high and low N application rates tend to decrease with the period of plant development. However, our results indicate that the late supply of N may contribute to a higher number of roots per plant in the final harvest.…”

“…However, cassava is normally grown in soils with low organic matter content and is therefore expected to exhibit a positive response to N fertilization (Nguyen, Schoenau, Nguyen, Van Rees, & Boehm, 2002) because N is the second most common nutrient taken up by cassava (Howeler, 1981). The application of N during the first vegetative cycle of cassava increases plant height (Oliveira, Uchôa, Alves, Albuquerque, & Rodrigues, 2017; Thummanatsakun & Yampracha, 2018; Uwah, Effa, Ekpenyong, & Akpan, 2013; Viana, Matsumoto, Sediyama, & Carvalho, 2005), the fresh biomass of shoots (Oliveira et al., 2017), the leaf area index (LAI) (Howeler, 2002; Kaweewong, Kongkeaw, Tawornprek, Yampracha, & Yost, 2013), and the storage root yield (Kaweewong et al., 2013; Oliveira et al., 2017; Sangakkara & Wijesinghe, 2014; Viana et al., 2005), demonstrating that an adequate supply of N is essential to obtain the greatest yield of cassava.…”