A23. Oil Palm Responses to N, P, K and Mg Fertilizers on Two Major Soil T ypes in Sabah. Soon B B F* and Hong H W*

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1 Oil Palm Responses to N, P, K and Mg Fertilizers on Two Major Soil T ypes in Sabah Soon B B F* and Hong H W* A23 ABSTRACT The results of N, P, K and Mg fertilizer trials on two major soil types of Sabah, namely Paliu and Lumisir Families, are presented. Nitrogen was the most important nutrient affecting FFB production on both soil types. The optimum yield was achieved at kg N per palm per year. An increment of 15-20% in FFB yield was attained with the application of N fertilizer. There was no yield response to K fertilizer on Paliu Family soil, but on Lumisir Family soil, K fertilizer increased FFB yield by 14%. P fertilizer markedly improved FFB yield by 13% on Paliu Family soil but this was not seen on Lumisir Family soil. There was no significant response of FFB yield to Mg fertilizer on both soil families. EFB improved FFB yield drastically on Paliu Family soil. There was a systematic increase in leaf N, leaf P and leaf K with the application of N, P and K fertilizers respectively on both soil types. K fertilizer had an antagonistic effect on leaf Mg. INTRODUCTION Oil palm (Elaeis guineensis) is an agricultural crop that requires optimum nutrients for sustaining growth and yield production. The main bulk of nutrient is supplied by soil. Fertilizers will compensate any deficit in nutrients required by the palms. Theoretically, the supply of fertilizers should be equal to that demanded by the palms. However, such ideal condition is rarely seen in the real world. The amounts of fertilizers required by the palms are dependent on a number of factors such as soil type, climatic conditions, previous land use, palm age and fresh fruit bunch (FFB) production. Without fertilizer, it is estimated that only onethird of the country s palm oil production can be achieved (Tarmizi, 2000). Most Malaysian soils, including those from Sabah, are inherently low in nutrients, particularly N and P (Goh et al., 1999). In actual estate practice, between two and ten folds of the actual quantities of nutrients were * Sawit Kinabalu Berhad, Jalan Kelapa Sawit, Km 4, Off Jalan Tuaran, Kota Kinabalu, Sabah, Malaysia. applied. The excessive nutrients applied will either be lost through leaching, soil erosion or volatilization. Thus, an understanding of the sitespecific, soil type and climatic conditions can help the estimation of a more accurate fertilizer rates. Several fertilizer field experiments on mature oil palm were carried out since the existence of Sawit Kinabalu Berhad (previously known as Sabah Land Development Board). Most of these trials were laid down on the major soil types of Sabah grown with oil palm. This paper discusses the results of some of these trials. ENVIRONMENT Trial 1- Paliu Family Soil The trial was established in 1990 on an existing 9 year-old DxP oil palm plots at Sg. Wakuba Estate (latitude 118 o 4 E and 118 o 8 E and longitude 4 o 17 N and 4 o 21 N), which is situated about 35 km from Tawau. The soil of the trial plot was dominated by Paliu Family (Orthic Acrisols), which was developed over sub-recent riverine alluvium. The chemical and physical properties of the soil prior to the commencement of the trial are given in Tables 1a and b. The terrain was flat. Mean annual rainfall for the duration of trial was 1,895 mm. July was the wettest month with about 232 mm of rainfall, while February was the driest month with about 102 mm of rainfall. There was no distinct dry spell in a year with a total of 138 rainy days per year (Table 3). Trial 2- Lumisir Family Soil The trial was established in 1982 on an existing 6 year-old DxP oil palm plots at Sg. Balung Estate, which is situated about 40 km from Tawau and adjacent to Sg. Wakuba Estate. The soil belongs to the Lumisir Family (Ferric Acrisols) that was developed over sub-recent to recent riverine alluvium. The chemical and physical properties of the soil prior to the commencement of the trial are given in Tables 2a and b. The terrain was flat. Mean annual rainfall for the duration of trial was 1,835 mm. November was the wettest month with about 240 mm of rainfall, while February was the driest month with less than 86 mm of rainfall. Rainfall was evenly distributed throughout the year with a total of 129 rainy days per year (Table 3). 244

2 Oil Palm Responses to N, P, K and Mg Fertilizers on Two Major Soil Types in Sabah MATERIALS AND METHODS The details of the experiment are given in Appendices 1 and 2. The design of the experiment was a 32 NK x 2P factorial design with two replications. In Trial 1, each plot consisted of 36 palms with the central 16 palms as recording palms whereas in Trial 2, each plot consisted of 30 palms with the central 12 palms as recording palms. The surrounding palms served as a guard TABLE 1a. PRE-TREA TMENT SOIL CHEMICAL ANALYSIS DA TA AT SG. WAKUBA ESTATE (Paliu family soil ) Treat Depth ph OC %N P(ppm) ExchCation(me/100g) CEC (cm) (H 2 O) Total Avail. Na K Ca Mg N N N P P K K K TABLE 1b. PRE-TREA TMENT SOIL PHYSICAL ANALYSIS DA TA AT SG. WAKUBA ESTATE (Paliu family soil) Treatment Depth Particle Size Distribution (%) (cm) Coarse sand Fine sand Silt Clay N N N P P K K K

3 TABLE 2 a. PRE-TREA TMENT SOIL ANALYSIS DA TA AT SG. BALUNG EST ATE (Lumisir family soil ) Depth Particle Size Distribution (%) ph Org. Total N Avail (cm) Coarse Fine Silt Clay in C (%) P Sand Sand H 2 O (ppm) > TABLE 2 b. PRE-TREA TMENT SOIL ANALYSIS DA TA AT SG. BALUNG EST ATE (Lumisir family soil ) Depth Exchangeable Cations (me%) CEC Total. Base (cm) Ca Mg K Na me/100g me/100g Exch Satn soil clay Bases (%) > TABLE 3. RAINF ALL DISTRIBUTION ( mm) OF SG. WAKUBA AND SG. BALUNG EST ATES Estate Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total Wakuba (11) (9) (10) (10) (12) (12) (14) (12) (10) (13) (13) (14) (138) Balung (11) (8) (11) (10) (11) (9) (12) (11) (8) (12) (14) (10) (129) Figure in bracket denotes total number of rainy days 246

4 Oil Palm Responses to N, P, K and Mg Fertilizers on Two Major Soil Types in Sabah row. Extra plots of magnesium and EFB mulching were incorporated to test the requirement of this nutrient and the effect of EFB on these soil series. The fertilizers were broadcast into two equal splits within the weeded circle. They were normally applied coinciding with the raining seasons in March and September. Upkeep and maintenance of the palms were carried out in accordance to normal estate practice. RESULTS Trial 1 Paliu Family Soil The effects of treatments on FFB yield and yield component on Paliu Family soil were summarized in Tables 4, 5 and 6. Treatments were applied in 1990, i.e. nine years after field planting. Significant increase in FFB yield was only noticeable three years after incorporation of fertilizers. The increase in yield was significantly attributed to the application of nitrogen (N) and phosphorus (P) fertilizers. N significantly affected yield improvement from year three onwards, with exception in year five where P significantly increased FFB yields from year four onwards (Table 4). Mean FFB yield was significantly increased by the applications of 0.75 kg N per palm per year and 0.30 kg P per palm per year by 15% and by 13% respectively. An additional dosage of 0.75 kg N per palm per year did not increase the yield further. There were significant interactions (P<0.05) in FFB yield between N and K in year 5 and between N and P in year 6, but this did not lead to a significant interaction in the mean FFB yield. Table 5 also shows that average bunch weight was significantly increased by an application of 0.75 kg N per palm per year. There was no further improvement in average bunch weight with the TABLE 4. FERTILIZER EFFECTS ON FFB YIELD ON PALIU SOIL OVER A PERIOD OF SEVEN YEARS ( ) FFB Yield (t/ha/yr) % Year of Treatment Mean Control N N N Var. Ratio ns ns ** ** ns ** * * P P Var. Ratio ns ns ns * ** ** * * K K K Var. Ratio ns ns ns ns ns ns ns ns Interaction NP ns ns ns ns ns * ns ns NK ns ns ns ns * ns ns ns PK ns ns ns ns ns ns ns ns NPK ns ns ns ns ns ns ns ns CV (%) LSD LSD NB: ns= non-significant; * significant at P = 0.05 and ** significant at P =

5 additional increase in rates of N fertilization. Although there were significant interactions between N and K and between N, P and K in average bunch weight. The significant interactions did not give significant effect on mean FFB yield. Generally, there was no significant effect of fertilizer treatment on mean bunch number per palm on Paliu Family soil (Table 6). There was no significant effect of potassium (K) on FFB yield, average bunch weight and bunch number per palm over the whole period of experiment. In the case of magnesium (Mg), Table 7 show that application of 0.16 kg Mg per palm per annum significantly decreased the number of bunches per palm. However, this decrease in number of bunch per palm did not lead to a significant decrease in FFB yield. This was because there was a slight improvement in the average bunch weight, which compensated the loss in bunch number, but the difference was not significant. The application of empty fruit bunches (EFB) at a rate of 275 kg per palm per year increased the mean FFB drastically (Table 7). This tremendous increase in FFB yield was attributed largely to the significant increase in mean bunch number per palm. Table 8 shows the treatment effects on the mean leaf nutrient level on Paliu Family soil. There were increases in leaf N and leaf K levels with the application of 0.75 kg N and 1.25 kg K per palm per annum respectively, but an additional rates of N and K fertilizers did not further increase the leaf N and K nutrient levels respectively. Similarly, an application of 0.30 kg P per palm per annum also increased the leaf P level. However, magnesium fertilization at a rate of 0.16 kg per palm per annum decreased the leaf Mg level. TABLE 5. FERTILIZER EFFECTS ON BUNCH WEIGHT ON PALIU SOIL OVER A PERIOD OF SEVEN YEARS ( ) Bunch W eight (kg) Year Treatment ABW (kg) N N N Var. Ratio ns ns * ** ** ** * * P P Var. Ratio ** ns ns ns ** ns ns ns K K K Var. Ratio * ns ns ns ns ns ns ns Interaction NP ns ns ns ns ns ns ns ns NK * ns ns ns ns ns ns * PK ns ns ns ns ns ns ns ns NPK * ns * ns ns ns ns * CV (%) LSD LSD NB: ns= non-significant; * significant at P = 0.05 and ** significant at P =

6 Oil Palm Responses to N, P, K and Mg Fertilizers on Two Major Soil Types in Sabah TABLE 6. FERTILIZER EFFECTS ON BUNCH NUMBER PER P ALM ON PALIU SOIL OVER A PERIOD OF SEVEN YEARS ( ) BN/palm Year Treatment Mean N N N Var. Ratio ns ns * ns ns ns ns ns P P Var. Ratio ns ns ns * ** * * ns K K K Var. Ratio ns ns ns * ns ns ns ns Interaction NP ns ns ns ns ns ns ns ns NK ns ns ns ns ns ns ns ns PK ns ns ns ns ns ns ns ns NPK ns ns ns ns ns ns ns ns CV (%) LSD LSD NB: ns= non-significant; * significant at P = 0.05 and ** significant at P = 0.01 TABLE 7. EFFECTS OF MAGNESIUM AND EFB ON YIELD AND ITS COMPONENTS ON PALIU SOIL Treatment Equivalent FFB Yield ABW BN/palm (t/ha/yr) (kg) kg Kies/p/yrkg Mg/p/yr kg EFB/p/yr Var. Ratio ns ns ** CV (%) LSD NB: ns= non-significant; * significant at P = 0.05 and ** significant at P =

7 Trial 2 Lumisir Family soil Table 9 shows the fertilizer effects on FFB yield, average bunch weight and bunch number per palm on Lumisir Family soil over a period of eleven years ( ). There was significant variation in these yield components caused by different rates of fertilizer application from year to year. The treatment of fertilizer came into effect in the second year after incorporation of fertilizer treatments. FFB yield was significantly increased at 2.50 kg K/palm/year while the rest of the treatments remained no effect at that particular year. The response of FFB yield to K fertilizer was very inconsistent. The treatment effect of K fertilizer was only observed in 4 out of the 11 years. However, it still affected the overall mean FFB yield at a significant level of 1%. The effect of N on FFB yield on Lumisir Family soil was more systematic. FFB yield was significantly increased by the urea treatment from the sixth year of fertilizer incorporation onwards. The overall FFB yield was significantly increased by 0.69 kg N/palm/year, but there was no significant effect at 1.38 kg N/palm/year. The response of FFB yield to P fertilizer was also not consistent. The treatment of P came into effect in the fifth year of fertilizer incorporation, but disappeared in the eighth year and returned into effect in the eleventh year. There was no significant difference in mean FFB yield between control and treatment plots. The significant increase in mean FFB yield by N fertilizer was contributed both by the significant increases in average bunch weight and mean bunch number. The significant increase in mean FFB by K fertilizer was attributed mainly to the average bunch weight. Table 9 shows that there were significant interactions between N and P, and between P and K in mean FFB yield. The interacted mean FFB yields were elaborated in Tables 12 and 13. In the absence of both N and P, mean FFB was significantly the lowest (Tables 12 and 13). There was no significant difference in mean FFB yield if either one of the elements, N or P, was present. K was a very important element in contributing to the increase in FFB yield. The significantly highest FFB yield was attained when the levels of K and P were at 5 kg KCl and 2 kg CIRP per palm per year respectively (Table 10). There were no significant increases in mean TABLE 8. FERTILIZER EFFECTS ON LEAF NUTRIENT LEVELS ON PALIU SOIL OVER A PERIOD OF SEVEN YEARS ( ) Treatments Equivalent Frond 17 Leaf Nutrient Level % DM N P K Mg Ca kg ACl/p/yr kg N/p/yr kg CIRP/p/yr kg P/p/yr kg MOP/p/yr kg K/p/yr kg Kies/p/yr kg Mg/p/yr kg EFB/p/yr

8 Oil Palm Responses to N, P, K and Mg Fertilizers on Two Major Soil Types in Sabah TABLE 9. FERTILIZER EFFECTS ON FFB YIELD ON LUMISIR SOIL OVER A PERIOD OF ELEVEN YEARS ( ) FFB Yield (t/ha/yr) % Year of Treatment Mean Control N N N Var. Ratio ns ns ns ns ns * ** ** ** ** ** ** P P Var. Ratio ns ns ns ns * ** ** ns ns ns * ns K K K Var. Ratio ns ** ns ns * ns ns ns * ns * ** Interaction NP ns ns ** ns ns ** ns ns ns ns ns * NK ns ns ns ns ns ns ns ns ns ns * ns PK ns ns * ns ns * ns ns * * ns ** NPK ns ns ns ns ns ns ns ns ns ns ** ns CV (%) LSD LSD NB: ns= non-significant; * significant at P = 0.05 and ** significant at P =

9 TABLE 10. FERTILIZER EFFECTS ON AVERAGE BUNCH WEIGHT ( kg) ON LUMISIR FAMILY SOIL OVER A PERIOD OF ELEVEN YEARS ( ) ABW (kg) Year Treatment Mean N N N Var. Ratio ns ns ns ns ns ns ** ns ns ** * * P P Var. Ratio ns ns ns ns ns ns * ns ns ns ns ns K K K Var. Ratio ns ns ns * ns ns ns ns ns ns * * Interaction NP ns ns ** * ns ns * ns ns ns ns * NK ns * ** ns ns ns ns ns ns ns * * PK ns ns ns ns ns ns * ns * ns ns ns NPK ns ns * ns ns ns ns ns ns ns ns ns CV (%) LSD LSD NB: ns= non-significant; * significant at P = 0.05 and ** significant at P = 0.01 FFB and average bunch weight by kieserite. However, the mean bunch number was significantly lower when the level of kieserite was at 0.50 kg/palm/year (Table 14). Leaf Nutrient Level There was a systematic increase in leaf N, leaf P and leaf K with the increased application of urea, CIRP and MOP respectively (Table 15). However, there was a negative relationship between leaf K and CIRP. The leaf K appears to be reduced as CIRP fertilization was increased. Kieserite did not show any meaningful response to leaf nutrient level. Profitability Analysis Table 16 shows the various revenues obtained from different combinations of fertilizer application on Paliu Family Soil. Regardless to whatever the price of FFB was, profitability analysis shows that N2P1K0 was the best option of fertilizer application on Paliu Family soil. Based on the above data, there was no need to apply K fertilizer on Paliu Family soil. 252

10 Oil Palm Responses to N, P, K and Mg Fertilizers on Two Major Soil Types in Sabah Table 17 shows the various revenues obtained from different combinations of fertilizer application on Lumisir Family soil. Statistical analysis shows that palms responded significantly at 1.5 kg Urea/palm and at 5.0 kg MOP/palm. However, profitability analysis produced a totally different result whereby fertilizer combination N2P0K0 gave the highest net revenue when FFB price was between RM and RM per metric tonne. This TABLE 11. FERTILIZER EFFECTS ON BUNCH NUMBER PER P ALM ON LUMISIR FAMIL Y SOIL OVER A PERIOD OF ELEVEN YEARS ( ) BN/palm Year Treatment Mean N N N Var. Ratio ns ns ns ns ns ns ns * ** ns * * P P Var. Ratio * ns ns ns ns ** * ns ns ns ns * K K K Var. Ratio ns ns ns ns ns ns ns ns ns ns * * Interaction NP ns ns ns ns ns * ns ns ns ns ns * NK ns ns ns ns ns ns ns ns ns ns ns ns PK ns ns ns ns ns ns ns ns ns ns ns ns NPK * ns ns ns ns ns ns ns ns ns ns ns CV (%) LSD LSD NB: ns= non-significant; * significant at P = 0.05 and ** significant at P = 0.01 TABLE 12. MEAN FFB YIELD AT DIFFERENT LEVELS OF N AND P 253 P N c 19.06b a 20.10ab ab 20.73ab

11 TABLE 13. MEAN FFB YIELD AT DIFFERENT LEVELS OF P AND K P K b 17.58b b 19.85ab ab 22.46a TABLE 14. EFFECT OF MAGNESIUM ON YIELD AND ITS COMPONENTS ON LUMISIR SOIL Treatment Equivalent FFB Yield ABW BN/palm (t/ha/yr) (kg) kg Kies/p/yr kg Mg/p/yr Var. Ratio ns ns * CV (%) LSD NB: ns = non-significant; * significant at P = 0.05 and ** significant at P = 0.01 TABLE 15. FERTILIZER EFFECTS ON LEAF NUTRIENT LEVELS ON LUMISIR SOIL OVER A PERIOD OF SEVEN YEARS ( ) Treatments Equivalent Frond 17 Leaf Nutrient Level % DM N P K Mg Ca kg Urea/p/yr kg N/p/yr kg CIRP/p/yr kg P/p/yr kg MOP/p/yr kg K/p/yr kg Kies/p/yr kg Mg/p/yr

12 Oil Palm Responses to N, P, K and Mg Fertilizers on Two Major Soil Types in Sabah difference was due to the high cost (RM / tonne) of MOP. The marginal value between N2P0K0 and N2P1K2 did not vary much even though the price of FFB increased from RM / t to RM /t. By taking into account FFB transport cost and fertilizer field application cost, N2P0K0 definitely outweighed N2P1K2 in term of money value. DISCUSSION The results of these two trials indicate that the response of N fertilizer was significant on both TABLE 16. PREDICTED PROFIT PER HECT ARE BASIS (RM/HA) FROM APPLICA TION OF DIFFERENT COMBINA TIONS OF N, P AND K FERTILIZERS ON PALIU FAMIL Y SOIL Fertilizer Fertilizer Cost Projected FFB Yield Net Revenue at different FFB Combination (RM) (t/ha) price (RM) N0P0K N1P0K N2P0K N0P1K N1P1K N2P1K N0P0K N1P0K N2P0K N0P1K N1P1K N2P1K N0P0K N1P0K N2P0K N0P1K N1P1K N2P1K NB: N0 = 0 kg ACl N1 = 3.0 kg ACl/palm N2 = 6.0 kg ACl/palm P0 = 0 kg CIRP P1 = 2.0 kg CIRP/palm K0 = 0 kg MOP K1 = 2.5 kg MOP/palm K2 = 5.0 kg MOP/palm * Fertilizer Cost (including transport cost from factory to estate) based on 136 palms/ha Ammonium Chloride = RM /t CIRP = RM /t MOP = RM /t ** Projected FFB Yield is based on seven years NPK trial data carried out at Sg Wakuba Estate on Paliu Family Soil Net Revenue = FFB price Fertilizer Cost Harvesting & Transport of FFB Manuring Cost Where Harvesting & Transport of FFB = RM 32.00/tonne Manuring Cost = RM 7.00 per 3 kg ACl or 2.5 kg MOP and RM 6.50 per 2 kg CIRP 255

13 Paliu and Lumisir Family soils. Application of N fertilizer on these two soils increased mean FFB yield by 15-20%. Optimum FFB yield could be obtained at 0.69 and 0.75 kg N per palm per year on Paliu Family soil and Lumisir Family soil respectively in which ammonium chloride and urea were used as N sources on Paliu and Lumisir Family respectively. These rates were comparable to 0.63 kg N per palm per year as reported by Kwan (1998) on Paliu Family soil. Response of FFB yield to N fertilizer varied for different soil types. In Peninsular Malaysia, Tan (1976) suggested about 0.88 kg N per palm per year for both Durian and Batu Anam soils while Foong and Syed Sofi (1987) showed that 0.83 kg N per palm per year was the most suitable rate. Teoh and Chew (1985) demonstrated that 0.57 kg N per palm per year for Munchong and Serdang soil series. Thus, in general, the response TABLE 17. PREDICTED PROFIT PER HECT ARE BASIS (RM/ ha) FROM APPLICA TION OF DIFFERENT COMBINA TIONS OF N, P AND K FERTILIZERS ON LUMISIR FAMIL Y SOIL Fertilizer Fertilizer Cost/ha Projected FFB Yield Net Revenue at different FFB Combination (RM) (t/ha) Price (RM) N0P0K N1P0K N2P0K N0P1K N1P1K N2P1K N0P0K N1P0K N2P0K N0P1K N1P1K N2P1K N0P0K N1P0K N2P0K N0P1K N1P1K N2P1K NB: N0 = 0 kg Urea N1 = 1.5 kg Urea/palm N2 = 3 kg Urea/palm P0 = 0 kg CIRP P1 = 1 kg CIRP/palm K0 = 0 kg MOP K1 = 2.5 kg MOP/palm K2 = 5 kg MOP/palm * Fertilizer Cost (including transport cost from factory to estate) based on 136 palms/ha Urea = RM /t CIRP = RM /t MOP = RM /t ** Projected FFB Yield is based on eleven years NPK trial data carried out in Sg Balung Estate on Lumisir Family Soil Net Revenue = FFB price Fertilizer Cost Harvesting & Transport of FFB Manuring Cost Where Harvesting & Transport of FFB = RM 32.00/tonne Manuring Cost = RM 7.00 per 3 kg ACl or 2.5 kg MOP and RM 4.00 per 1 kg CIRP 256

14 Oil Palm Responses to N, P, K and Mg Fertilizers on Two Major Soil Types in Sabah of FFB yield to N fertilizer was between 0.60 and 1.00 kg N per palm per year in Malaysian soil. There were only N and P fertilizer responses on Paliu Family soil. Kwan (1998) obtained the same responses with the same soil type in Sandakan. Normally, response of palm to P fertilizer is related to its soil P content. The positive response to P fertilizer was probably due to its inherent low P status in the soil as indicated in the pre-treatment soil chemical analysis (Table 1a). Foster et al. (1985) showed that a positive response to P fertilizer could be expected if soil available P in the weeded circle was less than 15 ppm. Moreover, the total P level of the Paliu Family soil was moderate (189 ppm) and the available P was low (16 ppm). P fixation may be a problem in this high silt soil (Gurmit, 1989). The soil exchangeable K of the Paliu Family soil was 0.14 me/100g, which was well below the critical level 0.20 me/100g. However, there was no corresponding increase in mean FFB yield (Table 1) even though application of K fertilizer increases foliar K content (Table 8). The lack of response to K fertilizer could be explained by the high silt content of the soil. The silt content of Paliu Family soil as shown in Table 1b was about 31%, which was very much higher than the value (19%) reported by Foster et al. (1985). Silt content, which is related to the soil buffering capacity, is negatively correlated to K fertilizer (Foster et al., 1985). Though available P of Lumisir Family soil in the weeded circle was below 15 ppm (Table 2a), there was no significant response to P fertilizer. The quantity of P fertilizer used in this trial was very minimal, i.e kg P per palm per year. Kwan (1999) reported that the responses to P fertilizer were generally from 0.92 to 1.84 kg P per palm per year in Sabahan soils. The significant interactions between N and P, and between P and K on Lumisir Family soil showed that with P fertilizer FFB yield could be further enhanced (Tables 12 and 13). It shows the importance of P fertilizer on FFB yield in this soil. Full responses of oil palm to N or K fertilizer on Lumisir Family soil depend on adequate P fertilization. Maximum FFB yield on Lumisir Family soil was obtained at 2.5 kg K per palm per year, using muriate of potash as the K source. The significant response to K fertilizer was due to the low exchangeable K in the soil, about 0.04 me/100g as against the critical level at 0.20 me/100g. Trials carried out in Peninsular Malaysia indicated that the suitable rate of K lies between 1.6 and 2.3 kg K per palm per year (Tan, 1976; Chan, 1982). On the other hand, work done by Kwan (1999) in Sabah showed that 2.8 kg K per palm per year was the most suitable rate. Results from the two trials indicate that both N and K fertilizers increased FFB yield through an increase in average bunch weight rather than bunch number. Many trials did not test the magnesium requirement of palms while carrying out NPK nutritional trials because magnesium was considered a secondary fertilizer in oil palm plantation. Profitable response to magnesium fertilizer appeared to be uncommon (Foster and Goh, 1976). The results show that there were no significant responses of Mg in the two soil families tested in Sabah. The fantastic increase in FFB yield by EFB application on Paliu Family soil was attributed to the increase in mean bunch number. This good response to EFB application was mainly due to the sandy condition of the soil and the lower rainfall (Chan et al., 1991). Leaf Nutrient Analysis There were systematic increase of leaf N, leaf P and leaf K to N, P and K fertilizers respectively in both Paliu and Lumisir Family soils. Contrary to expectation, application of Mg fertilizer depressed leaf Mg level in both soils. The negative response of leaf Mg to K application (Tables 8 and 15) on Paliu and Lumisir Family soils indicate that there was an antagonistic effect between leaf Mg and K fertilizer. Fertilizer Profitability Analysis On Paliu Family soil, the direct cost analysis shows that N2P1K0 was the best fertilizer combination with FFB price ranging from RM 100 to RM 200 per metric tonne. This fertilizer combination produced an average FFB yield of t/ha, which was about 7 t/ha more than the non-fertilized plot N0P0K0. The marginal value between N2P1K0 and N2P1K2 became smaller as the price of FFB increased. This indicates that N2P1K0 was more favourable when the price of FFB was low. On Lumisir Family soil, statistical analysis shows that N1P0K2 was recommended. However, the profitability analysis shows that N2P0K0, which produced t/ha, was more profitable even though N2P1K2 produced t/ha. The extra 1.38 t/ha produced by N2P1K2 was not enough to compensate the additional fertilizer cost. 257

15 However, the profitability analysis can only be used as a guide for manuring budget with reference to different FFB prices. A greater emphasis on growth and production is still needed. Otherwise, only a short-term profit is obtained, neglecting the growth of palms that leads to a subsequent reduction in FFB production. CONCLUSION On Paliu Family soil, the FFB yield response to N and P fertilizers was significant. Optimum N and P rates on this soil were found between 0.75 kg N and 0.30 kg P per palm per year. Mg fertilizer did not affect FFB yield but depressed the leaf K content. EFB application at a rate of 275 kg per palm per year increased FFB yield drastically. On Lumisir Family soil, results show that FFB yield response to N and K fertilizers was significant. The increase in FFB yield by N fertilizer was contributed both by average bunch weight and bunch number. While the increase in FFB yield by K fertilizer was attributed mainly to average bunch weight alone. P fertilizer did not show any significant effect on FFB yield, but the significant interaction between N and P, and between P and K indicates that without P fertilizer the full response of either N or K fertilizer would not be expressed. The application of K fertilizer had depressed leaf Mg level tremendously. There was a systematic increase in leaf N, leaf P and leaf K with the application of N, P and K fertilizers respectively on both soil families. ACKNOWLEDGEMENT The authors wish to thank the management of Sawit Kinabalu Berhad for permission to present this paper. Thanks and acknowledgements are also extended to staff of Agricultural Research and Services Unit of Sawit Kinabalu Berhad for compilation of experimental data. REFERENCES CHAN, K.W. (1982). Potassium requirements of oil palm in Malaysia: fifty years of experimental results. In: Proc. of Phosphorus and Potassium in the Tropics (eds. Pushparajah, E. and Shanfuddin, H.A.H.). Malaysian Society of Soil Science. Kuala Lumpur. p CHAN, K.W., LIM, K.C. and AHMAD, A. (1991). Fertilizer efficiency studies in oil palm. In: Proc. of the 1991 PORIM International Palm Oil Conference Agriculture (module 1) Progress, Prospects and Challenges towards the 21st Century (eds. Yusof, B., Jalani, B.S., Chang, K.C., Cheah, S.C., Henson, I.E., Norman, K., Paranjoithy, K., Rajanaidu, N., Mohd Tayed, D. and Ariffin, D). Kuala Lumpur. p FOONG, S.F. and SYED SOFI, S.O. (1987). Two 42 NK Factorial Fertilizer Trials on Rengam and Kuantan Series Soils In Mature Oil Palm. In: Proc. of the Int. Oil Palm Conference Progress and Prospects (eds. Abdul Halim, H., Chew, P.S., Wood, B.J. and Pushparajah, E.). Kuala Lumpur, p FOSTER, H.L. and GOH, H.S. (1976). Fertilizer requirements of oil palm in West Malaysia. In: International Developments in Oil Palm (eds. Earp, D.A. and Newall, W.). Incorporated Society of Planters. Kuala Lumpur. p FOSTER, H.L., TARMIZI A.M., MOHD. TAYEB D., CHOW, C.S., CHANG, K.C. and ZIN, Z.Z. (1985). The estimation of N and K fertilizer requirement of oil palm in Peninsular Malaysia. In: Proc. of the Int. Conf. on Soils and Nutrition of Perennial Crops (ICOSANP) (eds. Bachik, A.T. and Pushparajah, E.). Malaysian Society of Soil Science. Kuala Lumpur. p GOH, K.J., TEO, C.B., CHEW, P.S. and CHIU, S.B. (1999). Fertilizer Management in Oil Palm Agronomic Principles and Field Practices. Paper presented at Fertilizer Management for Oil Palm Plantations Course at Sandakan, Sabah. 44p. GURMIT, S. (1989). Fertilizer responses in Oil Palms on a Range of Alluvial Soils. In: Proceeding of 1989 PORIM International Palm Oil Development Conference. Kuala Lumpur. p KWAN, B.K.W. (1998). A 33 NPK Factorial Fertilizer Trial on Paliu Series Soil In Mature Oil Palm of Sabah. In: Proceedings Soil Science Conference of Malaysia 1998 (eds. Shamshuddin, J. and Fauziah, I.). Kuala Lumpur. p KWAN, B.K.W. (1999). Oil Palm Responses to Fertilizers under Sabah Conditions (unpublished). 27 pp. TAN, K.S. (1976). Efficient fertilizer usage for oil palm on inland soils. In: International Developments in Oil Palm (eds. Earp, D.A. and Newall, W.). Incorporated Society of Planters. Kuala Lumpur. p TARMIZI, A.M. (2000). Nutritional Requirements and Efficiency of Fertilizer Use in Malaysian Oil Palm Cultivation. In: Advances in Oil Palm Research. p

16 TEOH, K.C. and CHEW, P.S. (1985). Investigations on areas and frequencies of fertilizer application in mature oil palms. In: Proc. of the Int. Conf. on Soils and Nutrition of Perennial Crops (ICOSANP) (eds. Bachik, A.T. and Pushparajah, E.). Malaysian Society of Soil Science. Kuala Lumpur. p Oil Palm Responses to N, P, K and Mg Fertilizers on Two Major Soil Types in Sabah 259

17 APPENDICES Appendix 1. Details of T rial 1 Fertilizers Treatments Rate (kg/p/yr) Soil Unit : Orthic Acrisols (Typic Kandiudults) Soil Family : Paliu Family Parent Material : Terraced alluvium Design : 3 2 NK x 2P factorial, RCBD, 2 replicates Planting Material : DxP Planting density : 136 palms per hectare Year Planted : 1981 Treatment commenced/ceased : 1990/1996 Recording palms : 16 Plot boundary : one guard row Treatments Level Urea CIRP MOP Kies Urea Urea (46% N) CIRP Christmas Island Rock Phosphate (34.5% P 2 O 5 ) MOP Muriate of Potash (60% K 2 O) Kies Kieserite (26% MgO) Fertilizers Rate (kg/p/yr) Level ACl CIRP MOP Kies ACl Ammonium Chloride CIRP Christmas Island Rock Phosphate MOP Muriate of Potash (60% K 2 O) Kies Kieserite (26% MgO) Appendix 2. Details of T rial 2 Association Subgroup Soil Unit Soil Family Parent Material Design Planting Material Planting density Year Planted :1979 Treatment commenced/ceased :1984 :Brantian Association :Orhthexic Trepudult :Ferric Acrisols (Paleudults) :Lumisir Family :Terraced alluvium :3 2 NK x 2P factorial, RCBD, 2replicates :DxP :136 palms per hectare Recording palms :12 Plot boundary :one guard row 260