Tropentag, September 19 - 21, 2012 in Göttingen "Resilience of agricultural systems against crises"

Effects of Management Options on Soil Fertility Attributes, Weeds and Maize Yields on a Nitisol, Acrisol and Ferralsol of Western Kenya

¹Institute of Agricultural Research for Development (IRAD), Cameroon
²University of Bonn, Inst. Crop Sci. and Res. Conserv. (INRES) - Plant Nutrition, Germany

Abstract

Low soil fertility and high weed infestation are the main culprits for the declining maize production in western Kenya. Given the diversity of soil types and the resource endowment of farmers, the magnitude of this decline is likely to differ with farms. Seven organic and inorganic management options were compared with farmers' practice regarding their effects on soil fertility attributes and weeds in maize fields on three contrasting soils of western Kenya over two cropping seasons. Irrespective of the season, organic amendments were more effective than mineral fertilisers in enhancing soil carbon stocks and the labile and non-labile C fractions. The largest soil C content (4.1%) and C pool (72 Mg ha^-1) were observed on the clay Nitisol after two seasons of reduced tillage, while the lowest C content (1.1%) and C pool (22 Mg ha^-1) were observed on the sandy Acrisol with conventional tillage. The soil N supplying capacity increased with the application of both organic and mineral fertilisers and reached 210 mg kg^-1 after two weeks of anaerobic incubation of the mineral N-amended Acrisol. Bray-I P content reflected the P application rates and was highest (50-66 mg kg^-1) on the Acrisol with mineral P fertiliser use. Weed biomass accumulation and species composition differed with soil types and management options. Zero-tillage combined with the use of a cover crop had the lowest weed biomass (<30% of control) regardless of cropping season. A significantly negative relationship (P<0.01, r=0.37-0.51) was established between weed biomass and leaf area index of maize. These differential responses to management options in different soil types were reflected in maize grain yields with highest cumulative yields of 4.7-9.4 Mg ha^-1 a^-1 in the Nitisol and 1.4-7.4 Mg ha^-1 a^-1 in the Acrisol or Ferralsol. We may conclude that the tested technology options differentially affected soil fertility, weeds and production attributes. The extent of this response depended on the soil type, supporting the need for site-specific technology targeting.

Keywords: Bray-I P, C fractions, N supply, weed biomass, weed species composition

Contact Address: Ngome Ajebesone Francis, Institute of Agricultural Research for Development (IRAD), B.P. 2123, Yaoundé, Cameroon, e-mail: ngomajebeyahoo.com