Thursday, 13 July 2006

Benefits of Integrated Soil Fertility and Water Management in semi-arid region.

Robert B. Zougmoré, Institute for Environment and Agricultural Research (INERA), INERA, Ouagadougou, 04 POB 8645, Burkina Faso, Abdoulaye Mando, IFDC, BP 4483, Lomé, Togo, and Leo Stroosnijder, Wageningen University, Nieuwe Kanaal 11, 6709 PA, Wageningen, Netherlands.

Unreliable rainfall, inherent low soil fertility, and crust prone soils affect crop growth in the semi-arid zone in Burkina Faso, resulting in low crop yields and recurrent food shortage. Increasing population pressure requires enhanced soil, water, and nutrient productivity. More efficient use of rainwater and soil nutrients is essential in this region. The synergistic effect of soil and water conservation (SWC) measures and nutrient inputs emerged as the best way to reduce runoff and soil loss and to improve nutrient use efficiency and crop yield. This can be best illustrated through work conducted in partnership with INERA-Burkina Faso on the combined use of runoff barriers (stone lining or grass strips) and organic or mineral nutrient sources. Compared with control plots, the average reduction in runoff was 59% in plots with barriers alone, but reached 67% in plots with barriers + mineral N and 84% in plots with barriers + organic N. Plots with no SWC measure lost huge amounts of soil ( about 3 t ha-1 ) and therefore nutrients. The results of 2 years of measurement showed that annual losses from eroded sediments and runoff reached 84 kg ha-1 for OC, 16.5 kg ha-1 for N, 2 kg ha-1 for P, and 1.5 kg ha-1 for K in the control plots with no SWC measures. The total soil loss from plots with stone rows and grass strips were respectively as important as only 30% and 42% of the losses from control plots. The application of compost leads to the reduction of total soil loss by 52% in plots without barriers and by 79% when applied in plots with stone rows as compared to the losses in control plots. The application of urea in plots with and without soil conservation barriers also resulted in significant decreases in soil loss (Figure 6.1). Stone rows or grass strips without N input did not induce a significant increase in sorghum yield. Supplying compost or manure in combination with stone rows or grass strips increased sorghum grain yield by about 142% (0.8 t ha-1 versus 2.5 t ha-1), compared to a 65% increase due to mineral fertilizers (0.8 t ha-1 versus 1.7 t ha-1). The technology results in financial gains of about 145,000 to 180,000 FCFA ha-1 y-1 when adding N through compost to both stone rows and grass strips and about 70,000 FCFA ha 1 yr 1 when adding urea during a year with good rainfall. In drought years very little additional benefit is obtained from urea. Under the particular conditions of the experiment with moisture as a constraint, compost was more efficient because it provided not only nutrients but also contributed a lot to moisture conservation through improved soil structure. Results show the importance of combining SWC and nutrient management. Without nutrient inputs, SWC measures hardly affected sorghum yields, and without SWC, fertilizer inputs also had little effect. However, combining SWC and nutrient management caused a jump in sorghum yield.

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