Tankage

Tankage, a solid byproduct of animal waste rendering, is a potent local nitrogen source, containing over 5 times the nitrogen of most composts or aged manures. It's especially beneficial for nitrogen-demanding crops like corn and accelerates the decomposition of woody green residues. In Hawai‘i, tankage typically contains 8-9% N, 2.5-3.5% K, 0.75-1% P, and 5.0% Ca with a C:N of 5:1. Its low P content is due to its derivation primarily from fish scraps and waste meat, containing little bone. Tankage, also known as meat and bone meal, has been utilized in Hawai’i as an agricultural input for at least 20 years, recognized as National Organic Program (NOP) compliant for certified organic growers. Recommended application rates range from 2.2–4.4 metric tons/ha (1–2 tons acre), with higher rates suppressing yields. Preliminary recommendations for short-cycle vegetable crops are 1700–3400 kg/ha (1,500–3,000 lb/acre) per cycle, with residual nitrogen availability observed in subsequent cycles exceeding 2.2 metric tons/ha (1 ton/acre). Regular soil testing is advised to avoid nitrogen overapplication. Ongoing research aims to refine recommended rates for specific crops and soil types in Hawai‘i. Currently, production capacity in the state is approximately 67 metric tons (60 tons) per month, but increased production will be necessary for tankage to serve as a significant, sustained nitrogen source in Hawai‘i agriculture.

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