Building resilience against drought and soil erosion: impact of field water conservation in the drought prone Vertisol areas of northern Ethiopia

Field water conservation practices are a way forward to build resilience against drought through increasing productive green water and crop yield, while reducing runoff (blue water) and soil erosion. A long-term tillage experiment was carried out (2005 to 2011) on a Vertisol to quantify the impact of field water conservation practices on soil moisture, runoff, soil loss and crop yield in a rainfed field in northern Ethiopia. The experimental layout was a randomized complete block design with three replications on permanent plots of 5 m by 19 m. The tillage treatments were (i) derdero+ (DER+) with a furrow and permanent raised bed planting system, 30% standing crop residue retention and no-tillage on top of the bed, (ii) terwah+ planting system (TER+) with ploughing once at sowing, 30% standing crop residue retention and fresh broad beds, and (iii) conventional tillage (CT) with a minimum of three tillage operations and removal of crop residues. The crops grown in rotation were wheat, barley, teff and grass pea. The field conservation practices thus combined indigenous conservation practices (derdero and terwah) with the concepts of conservation agriculture (hence the ‘+’). Data on soil loss, runoff, soil moisture, crop yield and NDVI were collected. Significantly different (p<0.05) mean soil losses of 4.4, 12.5 and 18 t/ha/y were recorded for DER+, TER+ and CT, respectively. Similarly, the mean runoff was 458, 706 and 925 m3/ha/y from treatments with DER+, TER+ and CT, respectively. The average grain yield of wheat over three years was 2.46, 2.02 and 1.61 t/ha for DER+, TER+ and CT, respectively. NDVI records in wheat and grass pea were higher in DER+

Modifying wind profiles to improve the efficiency of noise barriers in wind. INTER-NOISE 2001, the 2001 International Congress on Noise Control Engineering, The Hague, The Netherlands. Manuscript on CD-ROM, 2001, 4pp.

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Integrated water and soil conservation for food security in Niger, preliminary results

As a result of growing population pressure and limited fertile land availability, Nigerien farmers increasingly rely on marginal lands for food crops production. These degraded lands, however, generally provide poor millet yields due to their low soil nutrient content and imbalanced partitioning of water in the root-zone. This study evaluates the agronomical, hydrological and soil quality parameters of water and soil conservation techniques (i.e. zaï, demi-lunes and no-till with scarification) which tackle these two major crop growth limitations by means of an in situ root-zone water balance experiment. Preliminary results from the first cropping season from June to October 2011 show overall low yields. The 2011 season was characterised by erratic rainfall with a severe dry spell during flowering stage. The control and manure treatment did not yield grain, but simply applying manure did increase dry matter production with a factor of 20. The highest grain yield was produced by the zaï, 134 kg/ha, which was 3 and 9 times better than respectively the grain yield of demi-lunes and no-till with scarification treatments. The zaï treatment moreover reduced cumulative actual evaporation as measured using mini-lysimeters during a 10 day drying cycle. In conclusion, until now the synergistic effect of the water-harvesting practices and the supply of manure show promising potential to rehabilitate and to increase the agronomic efficiency of marginal land in Niger. Future work will focus on the impact of the treatments on yield, soil quality properties and on the root-zone water balance.As a result of growing population pressure and limited fertile land availability, Nigerien farmers increasingly rely on marginal lands for food crops production. These degraded lands, however, generally provide poor millet yields due to their low soil nutrient content and imbalanced partitioning of water in the root-zone. This study evaluates the agronomical, hydrological and soil quality parameters of water and soil conservation techniques (i.e. zaï, demi-lunes and no-till with scarification) which tackle these two major crop growth limitations by means of an in situ root-zone water balance experiment. Preliminary results from the first cropping season from June to October 2011 show overall low yields. The 2011 season was characterised by erratic rainfall with a severe dry spell during flowering stage. The control and manure treatment did not yield grain, but simply applying manure did increase dry matter production with a factor of 20. The highest grain yield was produced by the zaï, 134 kg/ha, which was 3 and 9 times better than respectively the grain yield of demi-lunes and no-till with scarification treatments. The zaï treatment moreover reduced cumulative actual evaporation as measured using mini-lysimeters during a 10 day drying cycle. In conclusion, until now the synergistic effect of the water-harvesting practices and the supply of manure show promising potential to rehabilitate and to increase the agronomic efficiency of marginal land in Niger. Future work will focus on the impact of the treatments on yield, soil quality properties and on the root-zone water balance.C

Short term effects of conservation agriculture on soil erosion and agronomic parameters of Teff (Eragrostis Tef (Zucc.) Trotter) on the vertisols of Northern Ethiopian highlands

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Matric suction effect on distribution of stresses caused by vehicle wheels on a bare silty sand

Soil compaction in cropping systems, caused by the external pressure of machinery, creates impermeable layers that restrict water and nutrient cycles reducing agricultural production. To evaluate the matric suction effects on distribution with depth of stresses in a soil, caused by the use of agricultural machinery, Jet Fill tensiometers were installed at two different depths (i.e. 0.15 m, 0.30 m) in a soil profile constituted by silty sand with gravel (SM); to register the increments on subsoil vertical stresses, two miniaturized load cells (i.e. 16. 5 mm in diameter) were installed in a horizontal position under the centre line of the vehicle wheels’ path, at approximately 0.15 m and 0.30 m depth. Care was taken to calibrate the load cells in field conditions. A vehicle was made to pass over the soil surface, at a speed less than 5 km/h; the tyre inflation pressure applied on wheel was 380 kPa. Response of load cells to vehicle loading was evaluated at different average matric suction measured on soil profile. Finally, measured stresses have been compared with values obtained by applying well-known elastic theoretical methods used to assess stresses applied by tyres on bare soils. The corresponding results show that the increment of vertical stresses decreases as matric suction increases, and a good correlation between measurements and simulations of the increment on subsoil vertical stress.Soil compaction in cropping systems, caused by the external pressure of machinery, creates impermeable layers that restrict water and nutrient cycles reducing agricultural production. To evaluate the matric suction effects on distribution with depth of stresses in a soil, caused by the use of agricultural machinery, Jet Fill tensiometers were installed at two different depths (i.e. 0.15 m, 0.30 m) in a soil profile constituted by silty sand with gravel (SM); to register the increments on subsoil vertical stresses, two miniaturized load cells (i.e. 16. 5 mm in diameter) were installed in a horizontal position under the centre line of the vehicle wheels’ path, at approximately 0.15 m and 0.30 m depth. Care was taken to calibrate the load cells in field conditions. A vehicle was made to pass over the soil surface, at a speed less than 5 km/h; the tyre inflation pressure applied on wheel was 380 kPa. Response of load cells to vehicle loading was evaluated at different average matric suction measured on soil profile. Finally, measured stresses have been compared with values obtained by applying well-known elastic theoretical methods used to assess stresses applied by tyres on bare soils. The corresponding results show that the increment of vertical stresses decreases as matric suction increases, and a good correlation between measurements and simulations of the increment on subsoil vertical stress.C