In South America, factorial fertilisation trials were set up on oil palm estates managed by Palmeras de los Andes in Ecuador and Indupalma S.A. In Colombia to control fertilisation during the two oil palm crop cycles. These experiments were designed to determine the optimal leaf contents of N, P, K, Mg and Cl, in recent planting materials and to assess the impacts of the first crop cycle on the following cycle.

In the two presented trials, nitrogen and chlorine treatments were found to have the greatest impact on production after 10 years of monitoring. The observed leaf N and Cl deficiencies resulted in a significant effect on the average bunch weight, but these differences did not lead to significant differences in yield. However, after 10 years of monitoring, it was found that the yield differences between the highest and the lowest nitrogen rates (N2-N0) and between the highest and the lowest chlorine rates (Cl2-Cl0), increased steadily until reaching a threshold at which some authors consider that supplementary fertilisation is required. In both experiments, soil mineral reserves had not been tapped during the first oil palm crop cycle, which had benefitted from mean rational fertiliser rates of 3 – 5 kg palm^-1 yr^-1. These reserves were sufficient to limit a yield decline in the non-fertilised treatments. We also noted that it took a long time for the differences in leaf mineral content and yields to become significant, thus confirming that these are long-term effects. Hence, in a suitably fertilised plantation, it is very unlikely that the effects of fertiliser applications during previous years could be reflected by inter-annual yield variations. However, there is no reason to consider that the depressive effect of poor climatic conditions, such as prolonged drought, could be overcome by increasing early fertilisation.

Di Amerika Selatan, kajian pembajaan faktorial telah dijalankan di ladang sawit di bawah pengurusan Palmeras de los Andes di Ecuador dan Indupalma SA di Colombia bagi menyelia pembajaan dalam tempoh dua kitaran hayat sawit. Kajian ini direka untuk menentukan kandungan daun optimum N, P, K, Mg dan Cl dalam bahan tanaman terkini serta untuk menilai impak kitaran tanaman pertama pada kitaran berikut.

Setelah 10 tahun pemantauan, keputusan dua kajian tersebut menunjukkan nitrogen dan klorin mempunyai impak terbesar dalam pengeluaran hasil. Kekurangan N dan Cl dalam daun telah menyebabkan kesan yang ketara terhadap purata berat tandan tetapi tidak membawa kepada perbezaan hasil yang ketara. Walau bagaimanapun, selepas 10 tahun pemantauan, didapati bahawa perbezaan hasil antara kadar yang tertinggi dan yang terendah bagi nitrogen (N2-N0) dan klorin (Cl2-Cl0) meningkat dengan ketara sehingga mencapai suatu ambang yang memerlukan pembajaan tambahan. Kandungan rizab mineral dalam tanah didapati tidak digunakan semasa sawit dalam kitaran hayat yang pertama, yang mana sawit telah mendapat manfaat daripada kadar purata baja yang dibekalkan sebanyak 3 – 5 kg pokok^-1 thn^-1. Simpanan mineral ini mencukupi untuk menghadkan penurunan hasil sepertimana dalam plot tanpa rawatan baja. Kajian menunjukkan bahawa perbezaan dalam kandungan mineral daun dan hasil mengambil masa yang lama untuk menjadi ketara, sekali gus mengesahkan bahawa ini adalah kesan jangka panjang. Oleh itu, adalah sukar untuk membuktikan variasi hasil tahunan adalah terhasil daripada kesan pembajaan tahun-tahun sebelumnya. Namun begitu, pelaksanaan pembajaan awal bukanlah langkah yang perlu dipertimbangkan bagi mengatasi masalah yang boleh merendahkan hasil seperti kemarau yang berpanjangan.