Appropriate spacing enables the farmers to keep appropriate plant population in the field. Hence, it can avoid over or less population in a given plot of land which has negative effect on yield and quality of onion. Spacing of 40 × 20 × 10 cm between furrow, row and plants, respectively has been used for onion production in Ethiopia. But producers complain 10 cm intra row spacing produces large bulb size which is not preferred by consumer for home consumption. To optimize onion productivity, full package of information is required. To fill this gap field experiment was conducted to study the effect of inter and intra row spacing on the bulb yield and yield components of onion at Ribb in Fogera, Woramit in Bahir Dar and Koga in Mecha districts in 2014. The interaction of the lowest inter and intra row spacing mature earlier by 15 days compared to highest inter and intra row spacing. Forty nine percent of medium sized bulbs were produced with the interaction of 15 and 6 cm inter and intra row spacing while only 32% of medium sized bulbs were produced by the interaction of 25 and 8 cm inter and intra row spacing. Small sized bulb distribution decreased as intra row spacing increased while large bulb sized distribution increased when intra row spacing increased. The highest bulb weight (102 g) was produced by the interaction of highest inter and intra row spacing while the lowest bulb weight (45 g) was produced by the lowest inter and intra row spacing. Interaction of inter and intra row spacing of 15 and 4 cm respectively, scored the 1 st highest marketable bulb yield (39 ton ha-1) and interaction of 15 and 6 cm inter and intra row spacing scored the 2 st highest marketable bulb yield (36 ton ha-1). The result revealed that the earlier recommendation (20 and 10 cm inter and intra row spacing) produced more number of medium and large sized bulbs with a yield penalty of 8.0 and 10 ton per ha-1 compared to interaction of inter row spacing of 15 cm with intra row spacing of 6 and 4 cm, respectively. Therefore, the interaction of inter and intra row spacing of 15 with 6 cm is recommended as a first option for producers who wishes to produce maximum bulb yield with maximum medium sized bulbs. It is also confirmed that earlier recommendation is better as a second option for producers who wishes to produce for export market which requires medium and large sized bulbs of onion.

The experiment was conducted to study the effect of mulch on growth and yield of tomato varieties under polyhouse condition at Bahir Dar, Ethiopia in 2012 and 2013. The treatments were 4 × 2 factorial combinations of mulching material (Black plastic mulch (BPM), White plastic mulch (WPM), Grass mulch (GM) and no mulch with two varieties (Cochoro and Miya). White plastic mulch recorded significantly tallest plant height followed by black plastic mulch. Significantly highest number of primary and secondary branches per plant were recorded for un-mulched Cochoro variety and mulched with grass, respectively in 2013. Cochoro variety mulched with grass produced significantly highest number of flowers per cluster in 2013. Significantly highest number of fruits per cluster and percent fruit set was registered when Miya variety was grown on grass and black plastic mulch, respectively. Earlier flower, fruit set and maturity of fruits were recorded from plants mulched with white plastic. Significantly early flowering, fruit setting and fruit maturity were recorded inthe Miya variety. The highest marketable fruit yield was obtained with grass mulch treatment (60.90 t ha-1) and the lowest was obtained with no mulch treatment (43.76 t ha-1). The increase in fruit yield gained by the application of grass mulch in polyhouse was attributed to its favorable effect on soil temperature and soil moisture which subsequently created conducive condition for root growth and development. Significantly higher marketable yield was obtained in Miya variety (57.83 t ha-1) as compared to Cochoro variety (44.32 t ha-1). The mean air temperature regime was 18.7°C (night) to 25.6°C (day) inside the polyhouse which was optimum for plants growth and normal fruits production. Soil temperatures under both plastic mulches were constantly higher than under bare soil and grass mulch. Cost benefit analysis indicates the highest net benefit was obtained on grass mulch. Based on agronomic performance and economic analysis the result of the present study indicated that the superiority of Miya tomato variety grown at grass mulch under polyhouse growing condition. Therefore, application of grass mulch for tomato fruit yield using Miya variety is recommended for producers in the study area.

Although there is adequate information on the influence of plant population on root yield and size of carrot on flat and raised bed for rain fed production system, information on ridge-furrow bed preparation method is limited for irrigation production system. Therefore, in this study, field experiments were conducted for 2 years to determine the appropriate spacing of carrot on ridge-furrow carrot production practice under irrigation. Root yield increased significantly as the population increased. On the contrary, root size significantly decreased as population increased. The result of combined analysis over season and locations indicated that the narrowest spacing of 10 cm × 4 cm rows on the ridge and between plants, respectively, which accommodates 1,250,000 plants ha−1 gave significantly highest marketable carrot root yield of 26 t ha−1 followed by 22.6 t ha−1 with spacing of 20 cm × 4 cm which accommodates 1,000,000 plants ha−1, but it produced the smallest individual root weight of 83 g which is mostly preferred for household consumption unlike jumbo roots. Therefore, in terms of root sizes and marketable yield, the current study identified that spacing of 10 cm × 4 cm is optimum on ridge-furrow carrot production practices.

A field experiment was conducted with irrigation in 2018 and 2019 at three locations to identify the optimum plant density and adaptive variety for better watermelon yield and quality. It consisted of five densities (24,690, 13,888, 8,888, 6,172, and 4,535 plant ha−1) and two varieties (Crimson Sweet and Sugar Baby) with factorial combination in randomized complete block design with three replications. Plant density and variety were not affected by location and season. The response of watermelon in yield, quality, and growth was influenced by plant density and variety. The highest fruit yield of 32.1 t ha−1 was obtained from the highest plant density, which was statistically similar with the yield of 31.9 t ha−1 obtained with the second highest plant density. However, about 71% of the fruits produced with the highest plant density were mini-sized in the fruit size category, whereas only about 59% were mini-sized with the second highest plant density. Any addition of plant density beyond 13,888 ha−1 did not gain additional yield but reduced in quality attributes. Better fruit physical attributes and total soluble solid were recorded from the lowest plant density. Therefore, Crimson Sweet variety with 120 and 60 cm inter- and intra-row spacing, respectively, which accommodates the plant density of 13,888 ha−1, is optimum for watermelon production.