Tools for sustainable oil palm production. In situ fertilizer studies for plantations in Ecuador.

The objectives of this project are to: 1) develop a management tool for the Orellana Agricultural Cooperative (CAO) in order to assess the agronomic and economic results of fertilizers, and 2) use this study as a model to establish new fertilizer trials for other oil palm growers.

A Central Composite Design (CCD) factorial experiment was used to study the effect of five application rates of N, K and Mg fertilizer on the growth of immature plants and on fresh fruit bunch (FFB) yield. Twenty four plots of 36 plants were set in total, ten plots out of the 24 were the same reference or "central" N-K-Mg level. The onset of bunch production happened at the end of 2013.

We observed an increase of K demands and K effects with the onset of bunch production. In other words, while Mg was the main driver of plant growth in the immature phase, K became the most important element in the first years of production. For instance, for leaf dry matter production (LDM), Mg showed now a marginal linear negative effect only, while K was highly significant and its effect was exponential. The interaction between K and N was also significant. The highest LDM values (2.4 kg in leaf 17) were observed with the highest K dose and intermediate N rates. LDM was strongly correlated to fresh fruit bunch yield (FFB), but the effect of Mg on bunch yields was not confirmed and only K had an effect on actual FFB. The largest yields were observed with highest K rates, together with intermediate N and Mg rates (24 t FFB/ha). The increase in yield was driven mostly by an increase in bunch number instead of larger bunch weight.