George Yobe Kanyama-Phiri

Biodiversity can support a greener revolution in Africa

The Asian green revolution trebled grain yields through agrochemical intensification of monocultures. Associated environmental costs have subsequently emerged. A rapidly changing world necessitates sustainability principles be developed to reinvent these technologies and test them at scale. The need is particularly urgent in Africa, where ecosystems are degrading and crop yields have stagnated. An unprecedented opportunity to reverse this trend is unfolding in Malawi, where a 90% subsidy has ensured access to fertilization and improved maize seed, with substantive gains in productivity for millions of farmers. To test if economic and ecological sustainability could be improved, we preformed manipulative experimentation with crop diversity in a countrywide trial (n = 991) and at adaptive, local scales through a decade of participatory research (n = 146). Spatial and temporal treatments compared monoculture maize with legume-diversified maize that included annual and semiperennial (SP) growth habits in temporal and spatial combinations, including rotation, SP rotation, intercrop, and SP intercrop systems. Modest fertilizer intensification doubled grain yield compared with monoculture maize. Biodiversity improved ecosystem function further: SP rotation systems at half-fertilizer rates produced equivalent quantities of grain, on a more stable basis (yield variability reduced from 22% to 13%) compared with monoculture. Across sites, profitability and farmer preference matched: SP rotations provided twofold superior returns, whereas diversification of maize with annual legumes provided more modest returns. In this study, we provide evidence that in Africa, crop diversification can be effective at a countrywide scale, and that shrubby, grain legumes can enhance environmental and food security.

Maize and sesbania production in relay cropping at three landscape positions in Malawi

The relay cropping of sesbania (Sesbania sesban) — a N2-fixing legume — with maize (Zea mays) has been proposed as a strategy to increase soil fertility and food production in densely populated areas in southern Africa. We determined the production of relay-cropped maize and sesbania at three landscape positions under researcher-designed and farmer-managed conditions in southern Malawi. Three landscape positions (dambo valley or bottomland, dambo margin with < 12% slope, and steep slopes with > 12% slope) were examined in factorial combination with N sources for maize (no added N, relay-cropped sesbania, and calcium ammonium nitrate fertilizer). Relay cropping of sesbania with maize increased maize grain yield, as compared to unfertilized sole maize in two of three years. Split application of 96 kg N ha−1 as N fertilizer, however, was more effective than sesbania in increasing maize yields. Survival of sesbania seedlings and biomass production of sesbania were greater in the dambo valley and dambo margin than on steep slopes. Maize yields tended to be lower on steep slopes than in the dambo valley and dambo margin areas. Biomass production of sesbania and hence the potential benefits of intercropping sesbania with maize appear greater in the dambo valleys and dambo margins than on steep slopes.

Assessment of Nutrient and Biomass Yield of Medium and Long Duration Pigeon Pea in a Pigeon Pea-Groundnut Intercropping System in Malawi

Preliminary assessment of the performance of the medium and long duration pigeon pea in a pigeon pea-groundnut intercropping system was conducted at Chitedze Agricultural Research Station (S 130 59’ 23.2”, E0330 38’ 36.8”) in the 2011/2012 cropping season. An experiment involving eight treatments replicated three times in a randomized complete block design was established. Two pigeon pea varieties, long (ICEAP 04000) and medium duration (ICEAP 00557) and groundnut (CG 7) were grown as monocultures and intercrops. The intercrops involved planting either of the pigeon pea varieties with groundnut. Baseline soil data indicate that the soil pH was acid to moderately acid both in the top (mean=5.4-5.7) and the sub soil (mean=5.4-5.6) in all the treatment plots, with mostly low to marginally adequate total nitrogen content both in the top (mean=0.08-0.14%) and the sub soil (mean=0.09-0.13%). The soil organic carbon content was medium in the top soil (mean=0.9-1.6%) as well as sub soil (mean=1.1-1.6%) across the treatment plots. At the same time soil phosphorus was low to marginally adequate in the top soil (mean=16.8-27.6 mg kg-1) and marginally adequate in the sub soil (mean=20.8-25.6 mg kg-1), suggesting low soil fertility. The assessment of the above ground groundnut biomass indicate a mean yield range of 479-656 kg ha-1. While the assessment of the total biomass yield of the pigeon pea varieties indicate a mean yield range of 2,034-2,593 kg ha-1. In terms of estimated nitrogen yields returned to the soil, the medium duration pigeon pea-groundnut intercrop (mean=50.6 kg N ha-1) and the long duration pigeon pea-groundnut intercrop (mean=49.6 kg N ha-1) gave significantly (p 1.0) compared with the monoculture on equal land area. For the Malawian smallholder farmers, this suggests that mineral N supplementation in a legume-cereal rotation system for enhanced crop productivity might be less in the double legume-cereal rotation mode than in a legume monoculture-cereal rotation system. Normal 0 false false false EN-US X-NONE AR-SA

Preliminary results of a stocking rate trial in Lesotho

Forage responses to stocking rates and seasons were determined over a one-year period. The experimental design consisted of three stocking rates namely, light (2.0ha LSU-1), moderate (1.25ha LSU-1) and heavy (0.5ha LSU-1) and four seasons (autumn, winter, spring and summer) combined factorially in a Randomised Complete Block Design with three replicates per treatment. Data collected included aboveground available phytomass production, botanical composition and crude protein content. Total aboveground available phytomass production of forages at the end of the study period was significantly (P<0.05) lower in the heavy stocking rate than in the moderate and light stocking rates. Season significantly (P<0.05) reduced crude protein (CP) from 5.6% CP in summer and 7.8% CP in autumn to 4.2% CP in winter and 4.3% CP in spring. It is concluded that season exerted greater impact on sward productivity than stocking rate.

Merino sheep responses to different stocking rates and seasonal variation under rangeland conditions of Lesotho

Merino sheep responses to stocking rates were determined over a one-year period. The experimental design consisted of three stocking rates; light (2.0ha LSU-1), moderate (1.25ha LSU-1) and heavy (0.5ha LSU-1) in a Randomised Complete Block Design with three replicates per treatment. Data collected were live weight, grease fleece weight, staple length, fibre diameter and crimp frequency from ewes, and birth weight, growth rate, weaning weight and percent mortality from lambs. Ewes in the heavy stocking rate had significantly (P<0.05) lower final weight, grease fleece weight and fleece length than those in moderate and light stocking rates. Lambs in the heavy stocking rate had significantly (P<0.05) lower birth weight and weaning weight, but higher mortality than those in moderate and light stocking rates. It is concluded that heavy stocking rate significantly reduced ewe and lamb performances.