Soil Invertebrate Macrofauna: Population Dynamics and their Role in Litter Decomposition within a Hedgerow Intercropping in Embu, Kenya

Mwangi, Margaret Nyakinyua (2002) Soil Invertebrate Macrofauna: Population Dynamics and their Role in Litter Decomposition within a Hedgerow Intercropping in Embu, Kenya. Masters thesis, Kenyatta University.

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Abstract

Crop yields in Embu, Kenya, as in much of the developing world, are poor due to declining soil fertility caused by continuous cropping with few inputs. In low-input systems, soil biota regulates the transformation of organically bound nutrients into plant-available forms thereby enhancing food productivity. Management practice engaged may influence the nature of fauna population composition and structure and could lead to elimination/reduction of key groups and/or species of soil fauna and in some cases low abundances or biomass. A study was conducted during the long- and the short -rains of the year 2000 on-station at Embu in an ongoing experiment within hedgerows. The experiment had ten treatments replicated three times in randomized complete block design within hedgerows. The main experiment quantified the abundance of soil invertebrate macrofauna at three soil depths (0 - 10, 10 - 20 and 20 - 30 em) and established their relationship to soil chemical and physical properties within seasons. The macrofauna populations were monitored in soil monoliths of 25 em x 25 em x 30 ern. Soil cores and soil samples for physical and chemical analyses respectively, were taken from 5 different locations at 0 - 30 em depth within each plot at the start and at the end of each season. Simultaneously an experiment was conducted to investigate the role of soil macrofauna in litter decomposition and the relationship between litter quality and rate of decomposition. Two types of polyvinyl chloride litterbags with mesh SIze 7 and 1mm were used. The 7 mm mesh SIze allowed macrofauna to enter while the 1 mm excluded the macrofauna. Two types of litter: Calliandra calothyrsus Meissner and Leucaena leucocephala Lam de Wit were placed in the litterbags in duplicate in selected treatments of the Embu trials, and were sampled for chemical concentrations at 1, 2, 4, 8, and 16 weeks. Results from the study indicated that the composition and structure of soil invertebrate macrofauna varied with soil depths. Most faunal groups thrived well in the lower soil depths (20-30 em) than topsoil (0-10 em) layer/depths in hedgerows during the dry spell as opposed to during the wet conditions when the trend was reversed. Termites were the most abundant of the fauna observed. More fauna were recorded during the dry spell than when the conditions were moist. Hedgerow agroecosystem treatments that involved organic inputs offered a desirable niche for the macrofauna as opposed to those that entailed addition of inorganic fertilizer C. calothyrsus litter supported higher macrofaunal population than that of L. leucocephala. The macrofauna abundance, biomass and diversity were correlated to soil nitrogen, phosphorus, potassium, pH and compactness, but at varied levels. Soil invertebrate macrofauna enhanced the rate of decomposition of both litter types. Leucaena leucocephala decomposed and released nutrients faster than C. calothyrsus and the former had lower lignin and/or polyphenols to nitrogen ratio than the latter. The study endorses the potential of soil invertebrate macrofauna as biological indicator organisms of ecosystem status.

Item Type:	Thesis (Masters)
Subjects:	G Geography. Anthropology. Recreation > GE Environmental Sciences S Agriculture > SD Forestry
Divisions:	Africana
Depositing User:	Tim Khabala
Date Deposited:	19 Dec 2017 11:08
Last Modified:	19 Dec 2017 11:08
URI:	http://thesisbank.jhia.ac.ke/id/eprint/2989

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