Sulphur (S) has received limited attention by researchers, agronomists and planters involved in oil palm cultivation, despite the fact that the requirement at tissue level – as indicated by published critical concentrations in Frond #17 – is the same for S and magnesium (Mg) (0.2%). The continuous trend toward S-free fertilisers (urea, rock phosphate, KCl, dolomite) in Indonesia, together with high leaching rates of sulphate, have putatively reduced the S availability in many oil palm estates. However, this has rarely been addressed up to now. The BMP (Best Management Practice) project on sustainable oil palm intensification of the IPNI SEA programme carried out at six sites, which are representatives for current management practices in oil palm cultivation, revealed a very low S status throughout, as determined by the S concentration in Frond #17, with mean values of 0.12%-0.13% S. After evaluating available literature a downward adjustment of the published critical S concentration – considering a critical N:S ratio of 15:1 and a critical N concentration of 2.3% – 0.15% seems appropriate. Considering the more relevant adequate N concentration range of 2.4% – 2.8%, an adequate range for S of 0.16% – 0.19% is proposed. The results clearly indicate a very low S status even when evaluated using these adjusted critical S concentrations. Researchers, agronomists and planters are encouraged to pay more attention to the S supply and to the determination of S in foliar analysis. Until the proposed critical S concentrations are supported through experimental data, it is recommended that S-containing fertilisers are administered at S-deficient sites at about 1:10 of the N supply. Potentially, a wide range of S-containing fertilisers could be used. Kieserite (MgSO₄ . H₂O) seems particularly suitable due to its market availability and because both macronutrient elements contained are required in similar amounts by oil palm.

Keperluan sulfur (S) bagi tanaman sawit tidak diberi perhatian yang sewajarnya oleh penanam sawit dan ahli agronomi walaupun fakta menunjukkan bahawa nilai kritikal kepekatan S dan Mg untuk Pelepah 17 adalah sama (0.2%). Di Indonesia, penggunaan berterusan baja tanpa kandungan S (urea, batuan fosfat, KCl dan dolomit) serta kadar larut resap sulfat yang tinggi telah menyebabkan kedapatan S berkurangan di kebanyakan ladang sawit. Bagaimanapun, isu ini jarang diperbincangkan sehingga kini. Pihak IPNI SEA programme yang menjalankan projek amalan pengurusan terbaik (BMP) bagi sawit mampan di enam kawasan telah mendedahkan berlakunya keadaan status S yang sangat rendah dengan kepekatan S Pelepah 17 pada nilai purata 0.12%-0.13%. Selepas penilaian bahan rujukan, pelarasan menurun terhadap nilai kritikal kepekatan S dengan nisbah kritikal N:S pada nilai 15:1, maka nilai kritikal kepekatan N antara 2.3% hingga 0.15% adalah sesuai. Berdasarkan julat nilai kepekatan N yang mencukupi iaitu antara 2.4%- 2.8%, maka dicadangkan julat nilai kepekatan S yang mencukupi adalah antara 0.16%-0.19%. Keputusan ini jelas menunjukkan bahawa status S adalah sangat rendah walaupun dinilai dengan menggunakan kepekatan kritikal S yang telah dilaraskan. Para penyelidik, ahli agronomi dan penanam sawit adalah digalakkan untuk memberi lebih perhatian terhadap bekalan S serta kepentingan penentuan status S dalam analisis daun. Sehingga nilai kritikal kepekatan S yang dicadangkan dapat disokong dengan data penyelidikan, maka disyorkan penggunaan baja mengandungi S di kawasan mengalami kekurangan S iaitu dengan nisbah 1:10 dari kadar penggunaan N. Terdapat beberapa baja yang mengandungi S yang boleh digunakan, ini termasuklah kieserit (MgSO4 . H2O) yang mudah diperoleh di pasaran serta mengandungi dua makronutrien yang diperlukan dengan jumlah yang sama bagi keperluan sawit.