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An e-publication by the World Agroforestry Centre |
IMPERATA GRASSLAND REHABILITATION USING AGROFORESTRY
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4.4 Annual crops and intercropping 4.4.1 Site improvement for acid infertile soils
Imperata often occurs on very acid, infertile soils with not enough phosphorus (P) available for good tree growth and crop yields. On such soils, a heavy one-time application of rock phosphate (1 ton/ha) can improve the site greatly and help agriculture and agroforestry to succeed. Soil pH should be tested and a trial should be made of this method before it is applied over a wide area. If rock phosphate is unavailable, triple super phosphate and lime can be used instead. On land that is low in available P but has a pH greater than about 5.5, a soluble P fertilizer such as triple phosphate can be used alone. Where rock phosphate is unavailable or too costly for the farmers, it would be appropriate to seek outside assistance with credit or procurement. This procedure is best combined with legumes and green manure as in the following example.
Farmers may prefer to plant food crops immediately after the heavy fertilization. In that case, contour hedgerows may be planted instead of the leguminous cover crop.
Farmers grow upland rice and other crops on very infertile, acidic, hilly soils in East Pasaman, West Sumatra, Indonesia. Yields have become lower over the last 40 years as fallow periods shortened from 15 years to 5-6 years. An extension project assisted them to:
High yields of annual crops were achieved. Investment in Imperata rehabilitation was profitable after one year, even with working capital borrowed at 20% interest rates.
Annual crops can be intercropped with trees to provide short-term income. As the annual crops are planted and weeded, Imperata is kept out and the area has less fire hazard. Fruit, rubber, and other tree crops are an important investment, so cultivation practices for the annual crops should be careful not to damage or cause competition with the trees. If done correctly, the weeding and fertilizing of annual crops will benefit the tree crop. For example, fertilized chili peppers are a good intercrop for rubber trees. The farm family may only have enough labor to handle one to two hectares of annual crops. For establishing additional tree plantings, the family may rely on cover cropping (Section 4.3), herbicides and weeding, pressing and fuelbreaks. To reduce fire hazard, the annual crops should be:
Common intercrops include upland rice, sweet potato, beans, peanut (groundnut), tomato, peppers, squash, and ginger.
Field preparation
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