Data on standing biomass, mean annual increment of carbon stock, and nutrient accumulation in 40 industrial plantations at 21 sites in 11 countries are summarised. Aboveground biomass and mean annual increment of carbon near the harvest age, of these plantations ranged from 44 to 324 t ha-1 and from 3.1 to 22.9 tC ha-1 yr-1, respectively. Plantations managed on a short rotation are expected to accumulate carbon rapidly. However, there are large variations of biomass accumulation depending on site conditions. There is concern about the potential decrease of productivity caused by nutrient loss by intensive and repeated harvesting. It is important to determine the nutrients removed and conserve them as much as possible to prevent productivity loss and for sustainable management of industrial plantations. Careful management of the nutrient cycle through residue retention and fertiliser application is necessary to maintain high productivity.
Tag: cycling
Preface to workshop management of carbon in tropical soils under global change, science, practice and policy
It was first decided to organize a workshop on ‘Modelling of Soil Dynamic Practices’ in 1990 at the XIV International Soil Science Society (ISSS) Congress in Kyoto after the Committee on International Programs ~ (CIP) of ISSS-sponsored Symposium ‘V 8–Global Soil Changes and their Dynamics in a Changing environment’. This topic seemed redundant when we learned that our Canadian colleagues intended to focuson similar matters during their ‘Leth- bridge Symposium’ planned for 1992 (Wood and Dumanski, 1994). By letter exchange and intense discussion with those CIP members meeting in conjunction with the symposium on soil resilience and sustainable landuse September 1992 in Budapest, we opted for a meeting on carbon in tropical soils. We thought that a focus on the African savanna might be even more urgently required than emphasis on rice soils and wetlands, with the International Rice Research Institute (IRRI) there a potential host, and where high caliber expertise was available. Thus, we accepted Dr. Pedro Sanchez’s invitation to have our workshop at the International Center of Research in Agroforestry (ICRAF) in Nairobi, Kenya. Meanwhile the financial problem was settled by a donor group of German GTZ, National Aeronautics and Space Administration (NASA), United Nations Environmental Program (UNEP), United States Environmental Protection Agency (US-EPA), and the United States Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS). As the then chairman of the Standing Committee CIP of ISSS I should thank, besides the donors, in particular Dr. Pedro Sanchez, the Director General of ICRAF, our host and Dr. Mike Swift, Director of the Nairobi-based Tropical Soil Biology and Fertility Program (TSBF), who accepted the strenuous task of being the workshop conveners. Hereby I tacitly include their able cooperators. Our scientific co-sponsors, in addition to ISSS, ICRAF and the UNEP were TSBF and the International Geosphere Biosphere Program-Global Change in Terrestrial Ecosystems (IGBP-GCTE) through liaison of Mike Swift and Bernard Tinker.
Forest management and terraced agriculture: case study of Hani of Ailao mountains, Yunnan
This case study of the Hani in the Ailao mountains of Yunnan, China, highlights the importance of forests in providing local ecological services that are essential for the system of terraced agriculture. The paper investigates local people’s knowledge of these ecological services, including water regulation and nutrient recycling, as well as the gender differences in the local knowledge of these services. The paper notes that the Hani have maintained the forest condition quite irrespective of its tenurial status. Contemporary forest policies and reforestation in the area are also discussed.
SCUAF version 4: a model to estimate soil changes under agriculture, agroforestry and forestry
SCUAF is a computer model which predicts the effects on soil of specific land ue systems under given environmental conditions. It is designed to include the distinctive features of agroforestry that is, land use systems which include both trees and crops. This document discusses a new model, version 4, which is developed in conjuction with the Centre for Resource and Environmental Studies of the Australian National University
Nitrogen and phosphorus in African soils – what role for agroforesty?
The article looks at the role of agroforestry in nutrient cycling and focuses on the two main nutrients that limit production, namely nitrogen and phosphorus in a small-holder production system based on maize in Africa.
Tithonia diversifolia as a green manure for soil fertility improvement in western Kenya: A review
Tithonia diversifolia, a shrub in the family Asteraceae, is widely distributed along farm boundaries in the humid and subhumid tropics of Africa. Green biomass of tithonia has been recognized as an effective source of nutrients for lowland rice (Oryza sativa) in Asia and more recently for maize (Zea mays) and vegetables in eastern and southern Africa. This paper reviews the potential of tithonia green biomass for soil fertility improvement based on recent research in western Kenya. Green leaf biomass of tithonia is high in nutrients, averaging about 3.5% N, 0.37% P and 4.1% K on a dry matter basis. Boundary hedges of sole tithonia can produce about 1 kg biomass (tender stems + leaves) m1 yr1 on a dry weight basis. Tithonia biomass decomposes rapidly after application to soil, and incorporated biomass can be an effective source of N, P and K for crops. In some cases, maize yields were even higher with incorporation of tithonia biomass than with commercial mineral fertilizer at equivalent rates of N, P and K. In addition to providing nutrients, tithonia incorporated at 5 t dry matter ha1 can reduce P sorption and increase soil microbial biomass. Because of high labor requirements for cutting and carrying the biomass to fields, the use of tithonia biomass as a nutrient source is more profitable with high-value crops such as vegetables than with relatively low-valued maize. The transfer of tithonia biomass to fields constitutes the redistribution of nutrients within the landscape rather than a net input of nutrients. External inputs of nutrients would eventually be required to sustain production of tithonia when biomass is continually cut and transferred to agricultural land.