http://directory.umm.ac.id/Data%20Elmu/jurnal/A/Agriculture,%20Ecosystems%20and%20Environment/Vol79.Issue2-3.July2000/1567.pdf

Nitrogen use efficiency of taro and sweet potato in the humid lowlands of Papua New Guinea

No information is available on the decomposition and nutrient release pattern of Piper aduncum and Imperata cylindrica despite their importance in shifting cultivation systems of Papua New Guinea and other tropical regions. We conducted a litter bag study (24 weeks) on a Typic Eutropepts in the humid lowlands to assess the rate of decomposition of Piper aduncum, Imperata cylindrica and Gliricidia sepium leaves under sweet potato (Ipomoea batatas). Decomposition rates of piper leaf litter were fastest followed closely by gliricidia, and both lost 50% of the leaf biomass within 10 weeks. Imperata leaf litter decomposed much slower and half-life values exceeded the period of observation. The decomposition patterns were best explained by the lignin plus polyphenol over N ratio which was lowest for piper (4.3) and highest for imperata (24.7). Gliricidia leaf litter released 79 kg N ha(-1), whereas 18 kg N ha(-1) was immobilised in the imperata litter. The mineralization of P was similar for the three species, but piper litter released large amounts of K. The decomposition and nutrient release patterns had significant effects on the soil. The soil contained significantly more water in the previous imperata plots at 13 weeks due to the relative slow decomposition of the leaves. Soil N levels were significantly reduced in the previous imperata plots due to immobilisation of N. Levels of exchangeable K were significantly increased in the previous piper plots due to the large addition of K. It can be concluded that piper leaf litter is a significant and easily decomposable source of K which is an important nutrient for sweet potato. Gliricidia leaf litter contained much N, whereas imperata leaf litter releases relatively little nutrients and keeps the soil more moist. Gliricidia fallow is more attractive than an imperata fallow for it improves the soil fertility and produces fuelwood as additional saleable products.

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Leaf litter decomposition of Piper aduncum, Gliricidia sepium and Imperata cylindrica in the humid lowlands of Papua New Guinea

Sweetpotato (Ipomoea batatas L. Lam) is a tuber crop of immense potential as it produces more edible energy on marginal land than any other major food crop. As well as this useful property it can withstand adverse abiotic and biotic stresses and does not require intensive care. It therefore plays an important role in the economy of poor households where it acts as a major source of subsistence and is considered to be a ‘famine relief crop’. Besides this important function, the crop has immense industrial value for extraction of starch and production of animal feed. For all these reasons sweetpotato has great possibilities for enhancing food and nutrition security in developing and underdeveloped countries where most of the farmers’ holdings belong to the small and marginal categories. Although the crop is assuming greater significance owing to the ever-increasing population its importance is still underestimated and, unlike most staples, fails to attract sufficient attention of agricultural researchers throughout the tropics and subtropics. With greater attention and more collaborative research, there could be considerable improvements in the genetics of the crop and its husbandry which, together, would allow it to fulfill a wide range of needs in these areas of the world.

Crops that feed the world 5. Sweetpotato. Sweetpotatoes for income and food security

/pdf/yield-decline-of-sweet-potato-in-the-humid-lowlands-of-papua-46ibgqva56.pdf

Yield decline of sweet potato in the humid lowlands of Papua New Guinea

The effect of the indigenous cultural practices of in-ground storage and piecemeal harvesting of sweetpotato on yield and quality losses caused by sweetpotato weevil in Uganda.

R. M. Bourke

Papers

Sweet potato (Ipomoea batatas) production and research in Papua New Guinea.