Poor Utilization by Crops of Fertilizer Applied to Lahar
CROPS are unable to optimally use fertilizers applied on lahar-affected or coarse-textured soil due to leaching and volatilization of nutrients. Hence, researchers developed the controlled-release fertilizer (CRF) for these kinds of soil to provide plants with nutrients when needed without incurring high labor cost. CRFs are inorganic fertilizer granules sprayed with coating material that allows them to release plant nutrients at a controlled rate.
Controlled Release Fertilizers (CRF)
The following types of CRF were developed: a) di-ammonium phosphate (DAP) containing 13% nitrogen and 34% phosphorous; b) potassium chloride (KCl) containing 42% potassium; c) complete fertilizer containing 10-8-8% NPK; and d) urea containing 37% N.
Effect of CRF on Crop Yields
Pot tests for onion, rice, and tomato were conducted using clay pots filled with 8-kg lahar deposit. Results of laboratory tests for release patterns of nutrients and efficacy tests of CRF for onion, tomato, and rice revealed the following:
- Substituting the recommended rate (190-70-70 kg NP2O5-K2O/ha) of commercially available fertilizer (CAF) with one-half CRF increased yield of onion by 144%. Applying CRF at full recommended rate increased yield of onion by 259%.
- In tomato, substituting the recommended rate of CAF (90-60-60 kg NPK/ha) with half or full rate of CRF did not produce any yield.
- In rice, yield was higher by 50% when CRF was applied at recommended rate (150-35-35 kg NPK/ha).
- DAP and complete fertilizer release of nutrient contents were faster in the lowland than in the upland condition.
- Urea released nitrogen faster in soil in the upland, but released nitrogen faster in lahar in the lowland.
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