Abdoulaye Mando

Contribution of termites to the breakdown of straw under Sahelian conditions

Abstract The effect of termites on the breakdown of Pennisetum pedicellatum straw under Sahelian conditions was studied in northern Burkina Faso during the dry and wet seasons of 1995. Litterbags were laid on plots treated with drieldrin at a rate of 500 g a.i. (active ingredient) ha–1 to exclude termite activity and on untreated plots. Termites were the only macroscopically visible consumers which were observed in the litterbags during the dry and wet season. In litterbags with no termites present the rate of breakdown of straw was lower during both the dry or wet seasons than in litterbags with termites. In the litterbags with termites, much of the mulch was taken off and replaced by termite-made sheeting. From April to September over 60% of the added material disappeared from termite litterbags, while only 18% of the added straw disappeared from litterbags without termites. From October to December, 28% of the straw disappeared from termite-infested litterbags versus 8% from litterbags without termites. The contribution of termites to the breakdown of straw was estimated to be over 70% for each of the two experiments. Under Sahelian conditions, the breakdown of organic residues is strongly influenced by termites.

Long-term effects of mineral and organic fertilization on soil organic matter fractions and sorghum yield under Sudano-Sahelian conditions

Knowledge of changes in soil organic matter (SOM) fractions resulting from agricultural practice is important for decision-making at farm level because of the contrasting effects of different SOM fractions on soils. A long-term trial sited under Sudano-Sahelian conditions was used to assess the effect of organic and inorganic fertilization on SOM fractions and sorghum performance. Sorghum straw and kraal manure were applied annually at 10 t ha(-1), with and without urea at 60 kg N ha(-1). The other treatments included fallowing, a control (no fertilization), and inorganic fertilization only (urea, 60 kg N ha(-1)). Fallowing gave significantly larger soil organic carbon and nitrogen (N) levels than any other treatment. Total soil SOM and N concentrations increased in the following order: urea only 0.053 mm (particulate organic matter, POM). The POM concentrations in the control, straw and urea-only treatments were about one-half of the POM concentrations in the fallow treatment. POM concentrations increased in the following order: urea only <control <straw with or without urea <manure with or without urea <fallow. The fraction of SOM <0.053 mm (fine organic matter, FOM) was greater than POM in all plots except in fallow and manure+urea plots. Total N concentration followed the same trend as SOM, but cultivation led to a decline in both POM-N and FOM-N. Crop yield was greatest in the manure plots and lowest in the straw, control and urea-only plots. Results indicate that under Sudano-Sahelian conditions, SOM, POM and FOM fractions and crop performance were better maintained using organic materials with a low C/N ratio (manure) than with organic material with a high C/N ratio (straw). Urea improved the effect of straw on crop yield and SOM concentration.

Soil nutrient and sediment loss as affected by erosion barriers and nutrient source in semi-arid Burkina Faso

In semi-arid Sahel, soil erosion by water is one major factor accounting for negative nutrient balances in agricultural systems. A field experiment was conducted on a Ferric Lixisol in Burkina Faso to assess the effects of soil and water conservation barriers (stone rows or grass strips of Andropogon gayanus), the sole use of organic (compost) or mineral (urea) source of nitrogen (N), and the combined use of barriers and compost or urea nitrogen on soil nutrient and sediment erosion. The run-off barriers were put along contours. Organic carbon (OC) and nutrients losses through run-off and sediments were monitored during 2001 and 2002. Carbon and nutrient concentrations of generated sediments were very high, of 14–29 g kg−1 OC, 1.0–3.7 g kg−1 N and 0.32–0.71 g kg−1 total P. concentration in run-off water reached 0.023 g L−1 in stone rows treatments compared to only 0.002 g L−1 with treatments without barriers. Annual losses of organic C, N, P, and K were high and greatly dependant on soil loss magnitude. Compared to the control plots, soil losses were reduced on average by 84% during the 2 years with stone rows treatments, while by 71% with grass strips treatments. Compost application reduced soil loss by 75% in plots without barriers and by 89% in plots with stone rows as compared to control plots. With urea application, soil loss was on average 13% lower than in plots with compost. Integrated water and nutrient management can effectively alleviate soil, carbon, and nutrients losses by water erosion, therefore may contribute to intensifying crop production in Sahelian smallholder farming.

Economic benefits of combining soil and water conservation measures with nutrient management in semiarid Burkina Faso

Nutrient limitation is the main cause of per capita decline in crop production in the Sahel, where water shortage also limits an efficient use of available nutrients. Combining soil and water conservation measures with locally available nutrient inputs may optimize crop production and economic benefit in cereal-based farming systems. A study conducted in 2001 and 2002 at Saria, Burkina Faso (annual rainfall 800 mm, PET of 2000 mm yr−1) assessed the combined effects of two types of semi-permeable barriers (stone rows and grass strips of Andropogon gayanus Kunth cv. Bisquamulatus (Hochst.) Hack.) and the application of compost or urea on sorghum performance and economic benefits. The field experiment was carried out on a Ferric Lixisol, 1.5% slope and comprised 9 treatments in which the barriers were put along contours and combined with compost-N or urea-N. Installation of stone rows or grass strips without addition of nutrient inputs was not cost effective, although it induced sorghum yield increase (12–58%) particularly under poor rainfall conditions. Combining compost with stone rows or grass strips significantly increased sorghum yield that induced positive interaction effects (mean added effects of 185 kg ha−1 for stone rows combined with compost-N and 300 kg ha−1 for grass strips combined with compost-N). Economic benefits were substantial (109 480 to 138 180 FCFA ha−1) when compost-N was added to both stone rows and grass strips, whereas limited economic benefits were observed with the application of urea-N (1120 to 22 120 FCFA ha−1). This may provide farmers with capital to invest in soil management and may also contribute to poverty alleviation in sub-Saharan Africa.

Moisture conservation and fertilizer use for sustainable cotton production in the sub-humid Savanna zones of Nigeria

In the arid and semi-arid regions, soil moisture deficiency largely limits sustainable crop production. In the Nigerian dry Savanna (Northern Guinea savanna, arid and semi-arid zones), dry spells commonly occur between June and July, often lasts beyond three weeks. Rainfall is unevenly distributed and results in insufficient soil moisture for crop production. Soils at the uplands are commonly sandy loam to loamy sand at the surface horizons, have inherently poor fertility status, poor moisture retention capacity and rapidly degrade due to sheet erosion, continuous cultivation and overgrazing. The study on cross banding of ridges to conserve moisture and use of boron in association with nitrogen, and without boron was therefore conducted in Sabon Gari Garu areas in Katsina State, in the dry savanna of Nigeria during the 2007 and 2008 cotton cropping seasons. Data obtained were statistically analyzed. Results show that treatment with tied ridges + NPK + boron (415.70 kg ha−1 and 312.47 kg ha−1 cotton in respective years) resulted in significant higher cotton lint yields in 2007 and 2008 than NPK + boron treatments (245.20 kg ha−1 and 255.16 kg ha−1 cotton in 2007 and 2008, respectively). Cross banding of ridges is recommended for farmers to conserve soil moisture and application of NPK + boron fertilizers.

Socio-economic Determinants and Trends on Fertilizer Use in West Africa

A large number of people in Africa continue to grapple with food and nutrition insecurity largely due to insufficient food availability, inadequate incomes coupled with high rates of unemployment, risk and vulnerability as well as inadequate access to basic services. The situation has been exacerbated by emerging global socio-economic trends, population increase, land degradation, climate change and an undeveloped agricultural sector among many other causes (Bationo and Egulu, Status of implementation of Abuja declaration, 2013). It is estimated that Africa’s 226.4 million people are chronically hungry (FAO 2012).