Effect of Spacing on Yield of Maize (Zea mays L) and Artemisia (Artemisia annua L) intercrops in a Sub-humid tropical ecozone of Maseno – Kenya

Abstract

Artemisia (Artemisia annua L.) is a medicinal shrub whose extracts include artemisinin as the active ingredient that treats malaria in combination therapy, while maize (Zea mays L.) is a staple food crop in Kenya. An agroforestry (AF) production system that entails intercropping maize and artemisia with optimal component interactions could provide an alternative and viable llli\d use option. This study investigated the yield patterns of selected artemisia + maize intercropping spacings for optimum yield of maize and quality of artemisinin; with respect to land use potential in a sub-humid tropical climate. The experiment was carried out in two consecutive rain seasons interspersed with a short fallow period of 45 days from 2009 to 2010. There were 9 treatments, laid out in a RCBD design with 3 replications. Each replication had three different artemisia intrahedge spacing of O.75m, 0.90m and 1m from each hedge, and uniform displacements of 0.75m X 0.90m for maize. A control plot of maize+beans intercrop was used for comparative analysis of yield advantages using Land Equivalent Ratios (LER), with respect to artemisia+maize yield. The Replacerrient Value of Intercropping (RVI), Competitive Ratio (CR), Area-Time Equivalent Ratio (ATER), Cost-Benefit Analysis (CBA) and (Land Use Efficiency) LUE were the parameters used to evaluate yield potential of the artemisia+maize intercrops. Ensuing data were subjected to ANOV A using the Costat statistical package while means separation was done with Bartlett's LSD at 5% significance Level. Pearson's coefficient was used for correlation analysis of artemisinin yield and chlorophyll content of artemisia. There was no significant effect of the spacings tested on major morphological characteristics of either intercrop (P>0.05); but spacing had a significant effect on yield of maize and quality of artemisinin produced (P<0.05). The treatments had a significant effect (P<0.05) on LUE, CR, ATER and LER for both maize and artemisia. Unlike artemisia RVI (P>0.05), the treatments did not have a significant effect on maize RVI (P>0.05). The LER indices proved an overestimation of yield potential compared to ATER while maize+artemisia intercrops had a 34% more biological yield advantage than maize+beans system under the same management system. The artemisia treatments had a significant effect on artemisinin yield (P<0.05), by exhibiting a high mean of 0.8%. There was also a strong positive correlation between chlorophyll and artemisinin accumulation (r2 = 0.7), and when optimum artemisinin yields are desired, a spacing of T, (Artemisia 0.75m X 0.75m; Maize O.9mX O.75m) is recommended after producing the highest artemisinin level of 0.82%. When maize is the crop of choice for food security on basis of desired high grain yields, a spacing regime ofT, (Artemisia 1m X 1m; Maize O.90mX O.75m)was superior and is thus recommended for the purpose. In general however, T3 (Artemisia 1m X O.9m;Maize O.90mX 0.75m) and T6 (Artemisia O.90m X O.9m; Maize O.90m X O.75m) were most suitable on basis of economic and biological yield advantages respectively, to generate farm incomes of upto Ksh 82,500ha-' (USD 971 ha') and sustain food security from AF practices in Kenya or regions with similar agro-ecological zones to Maseno.