Tithonia diversifolia, a shrub in the family Asteraceae, is widely distributed alongfarm boundaries in the humid and subhumid tropics of Africa. Green biomass of tithonia hasbeen recognized as an effective source of nutrients for lowland rice (Oryza sativa) in Asia andmore recently for maize (Zea mays) and vegetables in eastern and southern Africa. This paperreviews the potential of tithonia green biomass for soil fertility improvement based on recentresearch in western Kenya. Green leaf biomass of tithonia is high in nutrients, averaging about3.5% N, 0.37% P and 4.1% K on a dry matter basis. Boundary hedges of sole tithonia can produceabout 1 kg biomass (tender stems + leaves) m–1yr–1on a dry weight basis. Tithonia biomassdecomposes rapidly after application to soil, and incorporated biomass can be an effective sourceof N, P and K for crops. In some cases, maize yields were even higher with incorporation oftithonia biomass than with commercial mineral fertilizer at equivalent rates of N, P and K. Inaddition to providing nutrients, tithonia incorporated at 5 t dry matter ha–1can reduce P sorptionand increase soil microbial biomass. Because of high labor requirements for cutting and carryingthe biomass to fields, the use of tithonia biomass as a nutrient source is more profitable withhigh-value crops such as vegetables than with relatively low-valued maize. The transfer oftithonia biomass to fields constitutes the redistribution of nutrients within the landscape ratherthan a net input of nutrients. External inputs of nutrients would eventually be required to sustainproduction of tithonia when biomass is continually cut and transferred to agricultural land
Tag: biomass
Relating plant diversity to biomass and soil erosion in a cultivated landscape of the eastern seaboard of Thailand
Plant diversity can affect ecological processes through effects on biomass and soil condition. A study was carried out in an agricultural watershed of Thailand to document plant species richness of different agricultural land uses and to assess its relationship with biomass and soil erosion. A nested sampling design of 20 x 20 m, 10 x 10 m, 5 x 5 m and 1 x 1 m quadrats was employed to study species richness of three categories of plants: herbaceous plants, shrubs and trees. Interviews were conducted with farmers who owned the cultivated fields where sampling plots were located. Plant diversity was assessed by computing Shannon index, Simpson index, and Species richness. Species utility index, which is the percentage of species identified as useful, was also estimated for each land use. Biomass was estimated using methodology recommended by FAO and soil erosionwas estimated using the universal soil loss equation (USLE). From among the different land use types, mixed orchard ranked first in terms of plant diversity while paddy ranked last. Land uses with monocropping of shrubs, such as cassava, pineapple and sugarcane had lower plant diversity than land uses with monocropping of trees, such as coconut and para rubber. Monocropping of eucalyptus was an exception. Rotations of monocrops, namely pineapplecassava and sugarcanecassava, or intercropping, namely coconutcassava, also had a higher plant diversity as compared to monocropping of shrubs. The highest species utility index of 61 was found in orchards, the lowest of 9 was found in Eucalyptus plantations. Plant diversity was found to have a significant positive correlation with biomass and a negative, though non-significant, correlation with soil erosion.
Allometric estimation of above-ground biomass and leaf area in managed Grevillea robusta agroforestry systems
Non-destructive methods for determining the biomass and leaf area of individual trees throughout their growing cycle are an essential tool in agroforestry research, but must be capable of providing reliable estimates despite the influence that management strategies such as pruning may have on tree form. In the present study, allometric methods involving measurements of the diameter of all branches provided reliable estimates of canopy leaf area and biomass for grevillea trees (Grevillea robusta A. Cunn.; Proteaceae) grown as poles, but proved unsuitable for routine measurements because of their time-consuming nature. An alternative, less laborious method based on measurements of trunk cross-sectional area immediately below the first branch of the canopy provided satisfactory allometric estimates of leaf area and canopy biomass. Trunk biomass was determined from measurements of tree height and diameter at breast height using established methodology based on the assumption that trunk volume may be calculated using a quadratic paraboloid model; biomass was determined as the product of trunk volume and the specific gravity of the wood. The theoretical basis, development and validation of allometric methods for estimating tree growth are discussed and their wider applicability to other agroforestry systems is assessed.
Tithonia diversifolia: variations in leaf nutrient concentration and implications for biomass transfer
Green leaf biomass of Tithonia diversifolia is high in nutrients and recognised as a potential source of nutrients for crops. We conducted a field survey in western Kenya to determine the variation in leaf nutrient concentrations in tithonia grown in naturalised hedges and agricultural fields, and to examine whether leaf nutrient concentrations were related to soil nutrient status. Leaf P and K concentrations were higher in naturalised hedges (3.2 g P kg1 and 35 g K kg1) than in unfertilised fields (2.2 g P kg1 and 23 g K kg1). The critical level of 2.5 g P kg1 for net P mineralisation was exceeded by > 90% of the leaves from hedges, but by only 14% from unfertilised fields. Leaf P and K concentration increased linearly with increasing natural logarithm of anion resin extractable soil P and exchangeable soil K, respectively. However, at the same levels of soil available P and K, field-grown tithonia consistently produced lower leaf P and K concentrations than that grown in hedges. This study indicates that biomass from tithonia planted on nutrient-depleted soils would be a less effective source of P and K, via biomass transfer, than tithonia from naturalised hedges.
Species screening for short-term planted fallows in the highlands of western Kenya
Short-term improved fallow technology, which is characterised by deliberate planting of fast growing N2 fixing legumes species in rotation with crops is currently being promoted for soil fertility replenishment in the small holder farms in the tropics. Recent research and extension efforts on this technology have mainly focused on a narrow range of species. There is a need to evaluate more alternative species in order to diversify the options available to farmers and hence reduce the risks of over dependence on fewer species. We evaluated twenty-two shrubby and herbaceous species for their site adaptability, biomass and nutrient accumulation, biomass quality and maize yield response to soil incorporated plant biomass after the fallow (six and twelve months) in three different field experiments on a Kandiudalfic Eutrudox in western Kenya. Species which yielded large amounts ofthe most biomass N adequate for two to three maize crops were Sesbania sesban, Tephrosia vogelii, Tephrosia candida, Crotalaria grahamiana, Dodonea viscosa, Colopogonium mucunoides, Desmondium uncinatum, Glycine wightii and Macroptilium atropurpureum. Most fallow species tested recycled 10%) and polyphenol (>2%) concentrations. were found only in the shrubby species, and the (Ppolyphenol + lignin ): N ratio varied widely (0.3–5) amongst the species. evaluated. Maize yield increased by two-fold in the first season following the fallow phase compared with continuous maize for most species. Results suggest that there are a wide variety of legumes that could be used for use in improved fallow technologies aimed at ameliorating nutrient degraded soils and subsequently enhancing crop yields.
Nitrogen uptake of maize (Zea mays. L) from isotope-labeled biomass of Paraserianthes falcataria grown under controlled conditions
Roots can be an important though poorly quantified source of nitrogen (N) in agroforestry systems. Nitrogen uptake of maize using P. falcataria below- and aboveground biomass separately, and their combination, as source of N, was assessed in a controlled experiment using 15N isotope labeling techniques. The 15N-direct and the 15N-indirect labeling techniques were compared for discrepancies in measuring N cycling from P. falcataria tree residues. N contribution to maize production was as follows; 40–57% from below ground biomass and 10–18% from above ground biomass (P < 0.05). Residue N use efficiency (%rNE) by maize was between 99 and 106% for belowground biomass, 4–4.5% for aboveground biomass. This implies that though nutrient release characteristics of aboveground biomass are commonly used as a basis for selection of agroforestry trees, those of belowground biomass would be of fundamental importance as well. Combining P. falcataria below and aboveground biomass did not result in significant (P < 0.05) effects on N recovered by maize, suggesting the absence of decomposition interactions between the two bio-chemically contrasting residues. There were no significant methodological differences reflected in measured N cycled by maize from leaves (Ndfr); 15% and 18% as estimated by 15N direct and indirect method, respectively. The two methods compared very well (P < 0.05) as tools of estimating N cycling from surface applied leaves. However, the ability of the direct method to measure N without disturbing either the tree or the soil, would make it a more attractive and valuable tool in N cycling studies in agroforestry systems.
Contributions of agroforestry research to livelihood of smallholder farmers in Southern Africa: 1. taking stock of the adaptation, adoption and impact of fertilizer tree options
Agroforestry practies involving fertilizer trees managed in sequential and simultaneous tree-crop systems are key to achieving sustainable food production in Southern Africa as they offer a wider scope for resource-stressed farmers to produce sufficient food for consumption and markets, even where land scarcity and soil fertility are major constraints. In these systems, maize yields have generally increased from less than a tonne per hectare to two or more tonnes, in Malawi, Tanzania, Zambia and Zimbabwe and they have been shown to be comparable to fertilized fields. Application of micro doses of inorganic fertilizers (especially N) in tree-crop systems has generally increased the synergy in nutrient availability thereby producing higher maize yields than unfertilized maize. Fertilizer tree systems are more productive and economically more profitable than unfertilized maize system and the economic impact is high, estimated at US
Multipurposes tree prunings as a source of nitrogen to maize under semiarid conditions in Zimbabwe. 2. Nitrogen-recovery rates and crop growth as influenced by mixtures and prunings
Time of pruning application and mixing prunings of varying qualities could be important management options to increase the rate of nitrogen recovery from multipurpose-tree prunings that are used as a source of nitrogen to crops. A field experiment was conducted in the semiarid zone of Zimbabwe to test this hypothesis, using prunings of calliandra (Calliandra calothyrsus) and leucaena (Leucaena leucocephala), alone and in mixtures, and maize (Zea mays) as the test crop. Time of pruning application significantly improved N uptake, N recovery, and grain yield of maize. Applying prunings of calliandra at maize planting was significantly better in terms of N uptake, N recovery, and grain yield than applying them four weeks after planting. However, with leucaena, time of prunings application had no significant effects on N recovery. Mixing prunings of leucaena and calliandra had no effect on maize N uptake, N recovery, and grain yield. Split application of available prunings during the crop growth cycle had no effect on N recovery compared to one-time application of entire amounts of prunings at planting.
Do agroforestry technologies improve the livelihoods of the resource poor farmers? Evidence from Kasungu and Machinga districts of Malawi
Fertilizer tree technologies such as intercropping, relay cropping, improved fallows and biomass transfer have been promoted as sustainable, low-input alternative or complimentary inputs to inorganic fertilizers in Malawi. However, research into the long term effects of their adoption on household food security and poverty reduction is limited. This study examined whether these technologies contribute to rural household of subsistence farmers in terms of food security and livelihoods improvement in two districts of Malawi.The study shows that fertilizer tree technologies increase crop production and provide additional income to households through sources such as sale of agroforestry tree seed and fuelwood. The choice of the technologies is driven by the size of the land holdings and more benefits are associated with large land holdings. While fertilizer tree technologies contribute to the reduction in hunger months, this is usually compromised at the household level by the inability to achieve livelihood security, absorb and cope with shocks and overall improved welfare.
Allometric equations based on a fractal branching model for estimating aboveground biomass of four native tree species in the Philippines
Fractal branching models can provide a non-destructive and generic tool for estimating tree shoot and root length and biomass, but field validation is rarely described in the literature. We compared estimates of above ground tree biomass for four indigenous tree used on farm in the Philippines based on the WanFBA model tree architecture with data from destructive sampling. Allometric equations for the four species varied in the constant (biomass at virtual stem diameter 1) and power of the scaling rule (b in Y = aDb), deviating from the value of 8/3 that is claimed to be universal. Allometric equations for aboveground biomass were 0.035 D2.87 for Shorea contorta, 0.133 D2.36 for Vitex parviflora, 0.063 D2.54 for Pterocarpus indicus and 0.065 D2.28 for Artocarpus heterophyllus, respectively. Allometric equations for branch biomass had a higher b factor than those for total biomass (except in Artocarpus); allometric equations for the leave twig fraction a lower b. The performance of the WanFBA model was significantly improved by introduction of a tapering factor”s” for decrease of branch diameter within a single link. All statistical tests performed on measured biomass versus biomass predicted from the WanFBA results confirm the viability of the WanFBA model as a non-destructive tool for predicting above-ground biomass equations for total biomass, branch biomass and the leaf twig fraction.