Interpretive Summaries:

Evaluation of the site-specific nutrient management (SSNM) technique continued in Asahan and Simalungun Districts (North Sumatra). In these two districts, a complete treatment of nitrogen (N), phosphorus (P), and potassium (K) included 115 kg N (10 kg N from ammonium sulfate and 105 kg N from urea), 36 kg P₂O₅, and 50 kg K₂O to produce 5.6 t/ha. The average yield of rice from seven farmers in Sipare-pare village (Asahan) was 4.1 t/ha (- N plot), 5.2 t/ha (- P plot), and 5.1 t/ha (- K plot). This pattern was also recorded in Totap Mojawa (Simalungun) using the same rates of N, P, and K fertilizer. The average yield of rice was 5.0 t/ha (- N plot), 5.7 t/ha (- P plot), 5.4 t/ha (- K plot), and 6.8 t/ha (complete NPK plot). A substantial increase in rice productivity is apparent with addition of P and K, provided adequate N fertilizer is applied.

An omission plot was also established in Madina and Deli Serdang Districts for information dissemination of technology development purposes. The rates of N, P, and K fertilizers were the same as applied in Asahan and Simalungun. Currently, the Agricultural Service in Asahan is willing to collaborate with the Agricultural Technology Assessment Institute (AIAT) to verify resulting fertilizer recommendations in eight sub-districts which were selected based on having similar soil status, plant requirements, and expected yield goals. After the concept has been proven practical, methods of dissemination will be developed.

In central Java, the technique has been conducted for four consecutive seasons in Kliwonan Village, Sragen District. Here, soil P is above 40 mg/100 g of soil (25% HCl extraction) and soil K is above 20 mg/100 g of soil (25% HCl extraction) and thus the response to applied P and K was not significant. The average yield for wet season 1 (WS1:October to February 2001/02) was 6 t/ha, 7 t/ha in WS2 (March to July 2002), and 8 t/ha in the dry season (July to September 2002). Overall results determined that: 6 t/ha rice in WS1 requires 25 kg P₂O₅/ha and 35 kg K₂O/ha; 7 t/ha rice in WS2 requires 30 kg P₂O₅/ha and 50 kg K₂O/ha; 8 t/ha rice in WS2 requires 35 kg P₂O₅/ha and 65 kg K₂O/ha. In various seasons, little difference in yield was found between SSNM plots and farmers’ practice plots. It was concluded that it would be more appropriate to apply P and K in alternate seasons instead of each successive season. Future activities will involve extending the technique to other locations within North Sumatra and Central Java. Indonesia-24