Abstract
Effects of organic inputs (OIs) on maize grain yield and chemical properties of Ultisols were assessed at Msekera and Misamfu Agricultural Research Stations in the medium and high rainfall regions respectively of Zambia. The OIs included biomasses of the leguminous species Cajanus cajan, Tephrosia vogelii, and Crotalaria juncea, in-situ composted native grasses and shrubs called fundikila, modified fundikila using Mucuna pruriens, and composted cattle manure, with chemical fertilizer as a control. After two crop growing seasons, cattle manure significantly increased soil pH, while modified fundikila significantly increased levels of soil organic matter. At Msekera, OIs increased levels of total N by 300%. At Misamfu, fundikila and Cajanas cajan increased total N by 35%. The OIs did not significantly increase available P and K at both sites. In the first season at Msekera, OIs had a higher mean maize yield (6075±368 kg/ha) than chemical fertilizer (3567±715 kg/ha). Maize yields for OIs in the second season did not differ significantly from those of the first season. At Misamfu the leguminous OIs Cajanas cajan and Tephrosia vogelii, had a lower combined mean maize yield (5405±242 kg/ha) than chemical fertilizer (7426±430 kg/ha) in the first season. A 70% decline in maize yield occurred on plots with leguminous OIs in the second season compared to the first season. Leguminous OIs generally performed better at Msekera than at Misamfu. At both sites, the traditional OIs, cow manure at Msekera, and fundikila at Misamfu had higher maize yields than leguminous OIs. We concluded that effects of OIs on soil chemical properties and maize yield vary with soil and climatic conditions and that these need to be considered when selecting OIs for use by farmers.
Highlights
Small scale resource poor farmers are the major producers of maize, the staple cereal crop in Zambia (Zambia Development Agency, 2011)
Cow manure and the mixed biomass had higher levels of K of about 2.4% compared to the leguminous organic inputs, most of which had less than 2% K except velvet beans which had 2.2% K
After two crop growing seasons, organic inputs significantly increased soil pH and total N in soils compared to baseline levels at Msekera in the medium rainfall region but not at Misamfu in the high rainfall region of Zambia
Summary
Small scale resource poor farmers are the major producers of maize, the staple cereal crop in Zambia (Zambia Development Agency, 2011). To promote sustainable agriculture among resource poor farmers who are unable to afford expensive chemical fertilizers and other purchased external inputs required to produce adequate yields of maize and other crops, a number of soil management practices that do not require leaving land fallow have been developed or proposed (Ogunlana, Salokhe, & Lund, 2006; Subbian, Lal, & Subramanian, 2000). Most such practices involve the use of organic inputs to improve soil fertility and are reported to eliminate the need for fallow periods, increase productivity and maintain soil fertility. According to Ogoke et al (2009) the use of organic inputs is usually the only viable options for small scale farmers without access to chemical fertilizers, which are believed to contribute to the rapid degradation of the fertility of soils when used in large quantities
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