The loss of soil from land surfaces by erosion is widespread and reduces the productivity of agricultural lands. Concurrently, due to increasing human population, agricultural land expansion and exploitation, soil erosion and nutrient loss are the major environmental problems in Ethiopia. This study was conducted to estimate annual losses of soil, soil nutrients and carbon due to rill erosion. The entire watershed was classified into 12 land mapping units (LMUs). Consequently, the cropland was delineated to estimate soil and nutrient losses. Dimensions of the rills were measured at different parts of the landscape, and rill volume of rill erosions was assessed in the field. Disturbed representative composite soil samples were taken from each LMU to estimate the main soil nutrients, and each soil nutrient was estimated using different methods. The result revealed that the amount of soil lost through rill erosion was found to be 3.17 t ha -1 year -1 . The average annual nutrient loss by the rill erosion was 41.4 kg ha -1 soil organic matter content, 2.4 kg ha -1 total N, 0.02 kg ha -1 available P and 0.3 kg ha -1 exchangeable K. The annual estimated cost of the soil nutrient lost (total N and available P) due to rill erosion was found to be 1341 USD. This cost would be used to replace the total N and available P nutrients lost through the addition of mineral fertilizers. Water erosion in the form of rill erosion was severely affecting soil fertility management and crop production in the study watershed. Hence, effective integrated watershed management interventions and farmland managements could combat soil erosion.

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Field studies were conducted for two consecutive years (2013 and 2014) to determine the effectiveness of different plant extracts and synthetic chemical insecticides for the control of onion thrips (Thrips tabaci) at Adigudom, Southern Tigray, Ethiopia. Two chemical insecticides including dimethoate 40% E.C and Lambda-cyhalothrin (Karate 5 EC), and five botanical extracts obtained from neem (Azadirachta indica A. Juss), Mexican marigold (Tagetus minuta L.), tree tobacco (Nicotiana glauca Graham) and Jimson weed (Datura stramonium L.) were tested for their controlling effect on onion thrips. The population dynamics of the thrips was monitored and population counts were made before and after the application of each of the treatments. The two years combined analysis indicated that there was a significant difference (p<0.05) in onion bulb yield where dimethoate, Tree tobacco, Karate, and Mexican marigold recorded significantly higher onion bulb yield than the control. Thirty and 37% more bulb yield was obtained in the Tree tobacco and dimethoate treated plots than in the control. Karate has had the highest effect in reducing thrips pest population in year one, though was on par with that of dimethoate, did well in the second year contributing to significant yield improvement against the control. There was no statistically significant difference among treatments in plant height, leaf number and bulb weight. From among the botanicals tested, tree tobacco had the best performance in controlling onion thrips and was comparable to those of dimethoate and Karate.

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