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Natural organic resources and nutrient balance in the farming systems of south-central coastal Vietnam

Hoang, T.T.H., Thuc, D.D., Chen, W., Mann, S. and Bell, R.W. (2015) Natural organic resources and nutrient balance in the farming systems of south-central coastal Vietnam. In: Sustainable and profitable crop and livestock systems in south-central coastal Vietnam. Proceedings of the final workshop, 5 - 6 March 2013, Quy Nhon, Vietnam pp. 20-28.

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The availability and recycling of organic resources in sandy soils plays an important role in nutrient balance and nutrient availability for crops. The current utilisation of organic materials on farms in south-central coastal (SCC) Vietnam and its implications for nutrient balance on farms in this sandy terrain are not known. In 2009, after a survey of households in three communes (An Chan commune, Phu Yen province; Cat Trinh, Binh Dinh province; and Ninh Phuoc, Ninh Thuan province) located in the sandy region of SCC Vietnam, 91 samples of organic materials were collected to examine the existing use of organic resources, their nutrient composition and their potential contribution in supplying nutrients to crops. The samples included six kinds of materials: cattle manure, buffalo manure, pig manure, sheep manure, plant residues (peanut stem, cassava leaf, maize leaf, straw) and ash from burning crop residues in the field. Farmers in the selected communes utilised different kinds of organic material for various purposes, such as fuel for cooking, soil amendment and animal feed. There were no significant differences in total carbon (C) and total phosphorus (P) content of the organic samples except for the lower C in ash. However, each kind of manure or other organic material had different composition depending on the animal type and amount of added materials, method of preparation and time of storage. Among different kinds of farmyard manure (FYM), pig and cattle manure had higher nitrogen (N) than sheep manure, but P and potassium (K) concentrations were not different among manures, while among crop residues, cassava had lower N and K than other plant residues.

Partial nutrient balance at the field-plot level in farming systems of SCC provinces was developed to quantify inputs and outputs of macronutrients (NPK) in fields over 1 year’s duration. Nitrogen balance was positive for rice–rice fields; however, N imports were less than exports in the other cropping patterns. Phosphorus imports exceeded P exports in all studied fields except for forages, whereas K exports always exceeded K imports regardless of whether one crop or two per year were grown. These results suggest that noticeable macronutrient losses occur out of fields, in managing crop residues, in FYM processing and in animal manure recycling but these are not necessarily losses from the farm. Further studies are needed to optimise nutrient cycling, and especially organic resources, in local farming systems. In the particular case of K, negative balances at the field level suggest a likely impact of this element in limiting crop yield.

Publication Type: Conference Paper
Murdoch Affiliation: School of Veterinary and Life Sciences
Publisher: ACIAR
Copyright: © Australian Centre for International Agricultural Research (ACIAR) 2015
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