Impacts of conservation bunds on crop yields in Degua Tembien, northern Ethiopia

Evaluation of the extensive soil conservation program underway was necessary if it contributed to the intended main objective of increased food production. This study was conducted to: determine the quantitative impact of conservation bunds on crop straw and grain yields yield-soil property relations and investigate farmers' practices and perceptions. The effects of conservation bunds and soil properties on yield were investigated at three villages of Degua Tembien Luvisols on peasant farm-holdings. Groups of plots representing conservation and degradation levels were selected for field measurements and soils collected for laboratory analysis. On wheat plots, conserved samples (G1) showed 47% and 59% increase in grain yield over soil loss plots of same land (G2) and unconserved plots uphill (G3), respectively. On straw yield, the corresponding increase was 49% and 59%. On faba bean, G1 showed grain yield increase of 32% and 33% compared to G2 and G3, respectively. The corresponding increase of straw yield on faba bean crops was 38% and 47%. Both crop yields showed positive correlations with silt and clay contents. Exchangeable base cations (square sup(+) Ca, square sup(+) Mg, K sup(+) and Na sup(+)) did not show difference on group comparisons which might be due to the adequate concentration in all groups, but had weak positive correlation on yield-base cation comparisons. Total nitrogen was at very low level of concentration. On faba bean plots G3 was higher compared to G1 and G2 and on wheat plots the same group was higher in concentration compared to G2. Differences in total nitrogen did not bring about yield increase which could be due to the relatively higher total nitrogen and instead plots had other constraints more importantly, moisturedue to the very shallow nature of the soil to store adequate moisture. Phosphorus correlated best with yield compared to other analysed nutrients. 103-105 The use of inappropriate agronomic package is one of the many factors contributing to the low yield of potato in Ethiopia. The optimum level of any one of agronomic practices varies with environment, purpose of the crop, cultivar and expected economic advantage. To this end a trial comprising different sizes of seed tuber, interrow spacing and frequency of ridgings was carried out at Adet Research Center for two consecutive years (1993-1994) with the main objective of determining the optimum seed rate, stem density and ridging frequency for ware and seed tuber potato production. The trial was laid out in 3E3 partially confounded design of two replications. The results reveal that marketable and total tuber yield, stem number/plant and number of tubers of different size grades were significantly (P0.01) influenced by seed tuber size and interrow spacing. Generally, as seed tuber size increased stem number/plant, optimum seed tuber size and ware potato, and marketable and total tuber yield seemed to increase. The narrower the spacing between rows, however, increased the stem density and seed tuber size grades. There were no significant differences among the tested ridging frequency levels. In conclusion, a stem density of 21/square m (55,555 population), seed size grade of 45-55 mm diameter at a spacing of 60 cm (28 q/ha seed rate) for seed potato production, and 16/square m (44,444 population), seed size grade of 45-55 mm diameter at a spacing of 75 cm (22 q/ha seed rate) for ware potato production together with ridging one in 3-4 weeks after crop emergence was found to be the optimum for high yields of potato production. Total and marketable tuber yields obtained at these rates were 283 and 226 q/ha which are by far higher than other levels tested.