The Essentials of Conservation Agriculture for Soil Quality, Crop and Water Productivity in Ethiopian Agriculture: A Review

In fact food security can be increased through improved land use and land management practices. In Ethiopia much of the increase in crop production in the past decade has been due to increases in area of cultivated. To what extent expansion can continue remains a question, therefore obtaining higher yield rates is the challenge of Ethiopia’s agricultural system. Conservation agriculture (mulching); which here refers to minimizing soil disturbance through no-till practice, application of organic mulch cover, and cropping in time; has the potential to improve soil quality, water, and crop productivity. The objectives of this critical review is to collect available information in similar production environments, indicators on the essential of CA contributions to soil quality, crop and water productivity both in dry and rainfall seasons of Ethiopian agriculture. Recently a study on the role of conservation agriculture indicates improve soil quality, crop yield and water productivity. In addition to this CA can be protect soil layer for erosions either wind or runoff, to optimize infiltration rate minimize runoff, to crate the path of soil it contributes micro nutrients move easily. So, reviewer concluded that conservation agriculture is potentially important to improve sustainable Ethiopian agricultural production and productivity. This agricultural practice (CA) should be able to adopt for irrigated and rain fed farms of Ethiopia.

plow have caused land degradation) and poor utilization of rain water that led to low crop productivity (Leye, 2007). Reports showed that Ethiopia loss 40-130 t ha -1 year -1 of soil from croplands that costs the country about 1.0-1.5 million tons loss of grain production per year (Abera et al., 2020). Reduction in soil fertility and soil quality are among major factors contributing to low adaptability of agriculture to insufficient and erratic rainfall in many parts of the country (Alemu and Mengistu, 2019;Ariti et al., 2015). Research on conservation agriculture in Ethiopia started early in 1980s (Georgis and Sinebo, 1993) with the focus of reducing heavy disturbance from frequent tillage operations by the traditional tillage implement, Maresha plow (Melesse et al., 2007). Reports on crop performance and soil productivity improvements in most trials of zero and minimum tillage showed varying results in different soils and rainfall conditions (Assefa et al., 2019;Assefa et al., 2021;Belay et al., 2020). In addition to this for irrigation seasons studies have examined drip irrigation in combination with CA is one of the best strategies for soil and water management that improves the cycles of vegetable production through increased water productivity (Yimam et al., 2020;Assefa, 2018). Application of surface organic mulch cover has been used to improve soil water retention, reduce soil temperature and reduce wind velocity at the soil surface and arid lands (Yimam et al., 2020;Bainbridge et al., 2001). Surface organic mulch can also improve water penetration by impeding runoff and protecting the soil from raindrop splash and reducing soil crusting (Munshower, 1994). In recent studies, the effects of conservation agriculture with irrigation improves crop yield and also soil carbon and nitrogen were increased (Assefa et al., 2019;Yimam et al., 2020;Belay et al., 2020). So, this review pepper was troubled to conservation agriculture (CA); which here refers to minimizing soil disturbance through no-till practice, application of organic mulch cover, and cropping in time; has the potential to improve soil quality, water, and crop productivity. Therefore the objectives of this review work is to collect available information in similar production environments, indicators on the essential of CA contributions to soil quality, crop and water productivity both in dry and rainfall seasons of Ethiopian agriculture.

History of Agricultural practice in Ethiopia
The history of tillage dates back many millennia when humans changed from hunting and gathering to more sedentary and settled agriculture mostly in the Tigris, Euphrates, Nile, Yangste and Indus river valleys (Hillel, 1991) as cited by (Hobbs et al., 2008). From those Ethiopia is the source of Blue Nile the agriculture is generally dominated by smallholder, rain-fed, low-input-low-output mode of production (Agerie, 2013) Since, Ethiopian farmers have been practicing excessive soil tillage using animal traction for thousands of years (Goe, 1987) as cited by (Getnet et al., 2015). Tillage is physical, chemical, or biological soil manipulation to optimize conditions for seed germination, emergence, and seedling establishment (Getnet et al., 2015;Lal, 1976). Smallholder farmers in Ethiopia practice traditional tillage systems using an ard plow called Maresha (Nyssen et al., 2011;Leye, 2007). Traditional tillage systems that involve repeated cultivations with the Maresha plow have caused land degradation) and poor utilization of rainwater that led to low crop productivity (Leye, 2007). Much of the increase in crop production in the past decade has been due to increases in area cultivated. To what extent expansion can continue remains a question, therefore obtaining higher yield rates is the challenge of Ethiopia's agricultural system.

Conservational Agricultural practice in Ethiopia
Soil and Water Conservation in Ethiopia has a long history. According to Beshah (2003) the traditional terraces in Konso constitute a spectacular example of a living cultural tradition stretching back to more than 400 years. The soil conservation practices, including minimum or no tillage have long been practiced by farmers with different approaches or systems in Ethiopia (Rockström et al., 2009). From the observation indigenously Ethiopian farmers were applied plant residue (mulching) for nursery and perennial crops like hop and coffee. This applied residue (CA) is used to protect sun light and conserve soil moisture for long time. Conservation agriculture and its associated package of best practices were introduced in 1980 (Abera et al., 2020). with the focus of reducing heavy disturbance from frequent tillage operations by the traditional tillage implement, Maresha plow (Leye, 2007). Whereas the adoption and expansion of conservation agriculture for Ethiopian farmers is still under expected. Agricultural policies input subsidy policies, investments in agricultural extension and access to markets in predicting are challenges for CA adoption (Marenya et al., 2015).

Crop production and productivity in Ethiopia
Both irrigated and rain-fed agriculture is important in the Ethiopian economy. Nevertheless, virtually all food crops (97 %) in Ethiopia come from rain fed agriculture, with the irrigation subsector accounting for only about (3 %) of the food crops (Awulachew and Merrey, 2007;Mendes and Paglietti, 2015). Cereals dominate Ethiopian crop production were grown on 73.4 % of the total area cultivated, by a total of 11.2 million farmers and obtained 12 million tons per year of cereals, which is 68 % of total agricultural production (Mebratu et al., 2015). Irrigated crops in medium and large-scale commercial farms are mostly cash crops, in particular cotton and sugar cane, but fruits and vegetables were also introduced (Girma and Seleshi, 2007). In small-scale irrigation schemes, irrigated crops are more diversified, but for the country as a whole, the main irrigated crops are cereals-maize, wheat, barley or teff, pulses, vegetables, root crops, fruits, and fiber crops (cotton) (Neelakantam and Naidu, 2016). Smallholder irrigators generally prefer subsistence crops rather than cash crops (Muhanji et al., 2011) and use irrigation to complement rain fed agriculture, i.e. Supplementary irrigation rain-fed, during the dry season, they use full irrigation to get additional income (IWMI, 2009).
According to Central Statistical Agency Ethiopia (2011); CSA (2019), the agricultural Sample Survey report of Ethiopia on area and production of crops as categorized grain crops, vegetables, root crops, and fruit crops. Crop production farms are classified as private smallholder rain-fed farms, Private smallholder dry season irrigation farms, and Commercial farms (Table, 1). Those farms coverage and productivity of grain crop shows a total land area of 15,270,526 hectares and 342, 17454.3 ton. Vegetables, It covers 1.96% at the national level and contributes 2.17% of the total crop production. Root crops, it covers 1.62% of the area under all crops at the national level. Fruit crops, it covers 107,890.60 hectares and obtained more than 7, 923, 66.5 ton per year.
As compared to farm type's crop productivity showed that irrigated farm is good productivity while rain fed and commercial farms are less productivity of grain, cereals, pulses and oilseeds. 2.1 N.B: Area of cultivated and productions of yield data taken from CSA for irrigated, rain fed and commercial while productivity of each was changed by researcher

Role of Conservation Agriculture for soil, crop and water productivity
There are numbers of soil and crop management practices that can increase the crop yields and water productivity (Yi et al., 2010). CA (Mulching) is a cropping practice that entails placing organic or inorganic or synthetic materials on soil close to plants to provide a more favorable environment for the growth and development of crops (Ranjan et al., 2017;Kumar and Lal, 2012). The application of mulching practices reduces soil evaporation, conserve soil moisture, suppresses weed growth, control soil structure and temperature, influences soil micro-organisms and increase crop productivity (Kader et al., 2017) and reduction of runoff and erosion (Ranjan et al., 2017). It dampens the influence of the environmental factor on the soil by controlling seasonal fluctuations in soil temperature (Ghosh et al., 2006). Especially, using a sufficient mulching layer could control both weed growth and soil temperature fluctuations (Ji and Unger, 2001). Moreover, the water holding capacity of soil is improved through mulch decomposition and humus formation (Liu et al., 2013).
Agricultural production increase under CA by improving soil physical properties and fertility (Bandyopadhyay et al., 2009). Mulching is very useful in protecting the roots of the plants from heat, cold, or drought or to keep fruit clean (Kumar and Lal, 2012). Mulching have also effective change in increasing horticultural crop production in water scarcity regions (Lal Bhardwaj, 2013). Additionally, organic mulch protect the crop from soil born disease and provided plant nutrition (Stirling and Eden, 2008) and nutrients leaching loses can also be minimized (Zibilske and Makus, 2009) and improve crop production through increasing soil quality by conserving soil moisture (Ranjan et al., 2017), enhancing soil biological activities, and improving the chemical and physical properties of soil (Bandyopadhyay et al., 2009).
Conservation Agriculture with Drip Irrigation for Water Productivity in Sub-Saharan Africa including Ethiopia studied by Assefa et al. (2019) suggested that irrigation water use was substantially lower under CA, 18% to 45.6%, with a substantial increase in crop yields, 9% to about two-fold, when compared with CT practice for the various vegetables.
growth, and grain yield over none mulch (Kar and Singh, 2004). Straw mulching has the ability to improving the soil structure, water-holding capacity, and increase the soil moisture content of the soil, and the amount of water stored in soil increased as the application of mulching rate increases (Liu et al., 2013).
Organic mulches preserve more soil moisture (Ghosh et al., 2006) and (Teame et al., 2017). Mulch played a dominant role in the conservation of soil water even if in the condition of moderate stress (Mukherjee et al., 2012). Organic mulch consistently helped in retaining higher soil water than without mulch and reduced soil temperature by 2-3oc (Ghosh et al., 2006).
Moisture contents of soils of irrigated tomato under grass straw, rice straw, rice husk and sawdust mulches were higher than those in the non-mulching (Nkansah et al., 2003). Liu et al. (2010) studied soil water dynamics and water use efficiency in spring maize field under different water management practices on the loess plateau and the result indicates that soil water storage increased in the straw mulch compared to film mulch. Dissimilarly, (Shirgure et al., 2003) study reported that black polyethylene mulching conservation higher soil moisture than soybean straw and grass mulching. Straw mulching increases the soil moisture content of apple orchard (Liu et al., 2013) and maize crop (Tao et al., 2015). Straw mulch conserves soil water by reducing the incoming solar energy, less water was evaporated and mulch reduced the soil moisture depletion in irrigated potato plant (Kar and Kumar, 2007).
In most cases, water stored in the soil increases with increasing mulching rate. Ji and Unger (2001) reported that straw mulching rate increases form 2.0 Mg ha −1 to 4.0 Mg ha -1 soil water storage efficiency increase by 60 to 100%, respectively compared with bare soil. Harmoniously, Ahmed et al. (2007) suggested that soil moisture content increase from 2 to 24 % as the mulching rate increase from 1 to 4 tons per hectare. The effectiveness of increasing mulching rate on soil moisture reserve was studied by Uwah and Iwo (2011), the result indicated that soil moisture reserves were highest at mulching rate increases compared with non-mulch.
In Ethiopian case Liben et al. (2018) experimental report showed that CA increases by the rate of water infiltration 15%, time-to-pond doubled and soil organic carbon 4 g kg-1 as compared with conventional practice.

Essential of CA for plant growth and yield
Application of organic mulch more over straw mulching is superior to that of inorganic mulch to provide the highest yield of crops (Ghosh et al., 2006) and facilitate better crop growth and development (Teame et al., 2017). Organic mulching is one of the suitable methods for the production of horticultural and vegetable crops with quality products (Ranjan et al., 2017). Organic mulch increase yield to the extent of more than 50 % if the soil moisture is conserved (Ranjan et al., 2017). Saeed and Ahmad (2009) stated that organic mulches with or without gypsum to the soil being irrigated with saline water increases the yield of tomato by reducing salinity. Seifu et al. (2017) suggested that organic mulching has a significant effect on plant height and earliness maturity of garlic crops than bare soil. Identically, Teame et al. (2017) reported that straw mulch increases number of seed per capsule, seed weight, and grain yield of sesame. In contrast 7148 (Malik et al., 2017) reported that Black Film Mulch significantly increased the yield of sugar beet by 4% over straw mulch. Ghosh et al. (2006) suggested that wheat straw mulch increase yield of ground nut by 30-40% over without mulch and wheat or paddy straw produced 17-24% of higher yield of ground nut over polythene mulch. In contrast Liu et al. (2010) , suggested that maize grain yield was increased in film mulch rather than straw mulch. Mukherjee et al. (2012) reported that mulching increases tomato yield by 23-57% over non mulching condition. Maize yield was increased by 233.9 kg/ha-381.8 kg/ha in chopped straw mulching over prostrate whole straw mulching (Tao et al., 2015). In Ethiopia reported by (Liben et al., 2018) studied at Melkassa and Bako agricultural research center who obtained maize grain yield was 10.14 Mg ha-1 for conventional practice compared with 9.01 Mg ha-1 for CA in 2015 at Bako, but maize yields were greater with CA at Melkassa in 2016. Monoculture and intercrop dry bean, respectively, had 40 and 32% more grain yield with CA compared to CP in 2016 at Melkassa. It was concluded that medium-term beneficial effects of CA on soil properties and crop productivity can be expected at Melkassa, but any short-term benefits of CA at Bako were uncertain. Mubarak and Hamdan (2018) suggested that mulching increase onion bulb yield by 53.4% compared to none mulching. According to Inusah et al. (2013) onion bulb yield was improved under straw mulching rather than non-mulching. Onion yield in both grass and rice straw mulches were significantly different from one another; onion yield under grass mulching was increased by 60% than rice straw mulching. Therefore, the sustained yield of onion crop is achieved by mulching.

Essential of CA on water productivity
A lot of studies argued that conservation agriculture showed CA is one of the water management practice for increasing water productivity as well as increasing irrigable area (Biswas et al., 2017;Assefa, 2018;Belay et al., 2020;Assefa et al., 2021;Yimam et al., 2020). The study of Mukherjee et al. (2012), indicated that CA increased water productivity of tomato crop by 54-93%.
According to Igbadun et al. (2012) mulching with rice straw and black polyethylene significantly improve