Deep Tillage Improves Degraded Soils in the (Sub) Humid Ethiopian Highlands

Intensification of rainfed agriculture in the Ethiopian highlands has resulted in soil degradation and hardpan formation, which has reduced rooting depth, decreased deep percolation, and increased direct runoff and sediment transport. The main objective of this study was to assess the potential impact of subsoiling on surface runoff, sediment loss, soil water content, infiltration rate, and maize yield. Three tillage treatments were replicated at five locations: (i) no tillage (zero tillage), (ii) conventional tillage (ox-driven Maresha plow, up to a depth of 15 cm), and (iii) manual deep ripping of the soil’s restrictive layers down to a depth of 60 cm (deep till). Results show that the posttreatment bulk density and penetration resistance of deep tillage was significantly less than in the traditional tillage and zero-tillage systems. In addition, the posttreatment infiltration rate for deep tillage was significantly greater, which resulted in significantly smaller runoff and sedimentation rates compared to conventional tillage and zero tillage. Maize yields were improved by 6% under deep tillage compared to conventional tillage and by 29% compared to no tillage. Overall, our findings show that deep tillage can be effective in overcoming some of the detrimental effects of hardpans in degraded soils

Drip irrigation and service provision of irrigation water: New ways to step into affordable small scale irrigated agriculture

United States Agency for International Developmen

Effect of deficit irrigation on yield, quality and grower returns of native spearmint and hops in Washington State

This study analyzed the effects of water stress levels on the yield, quality, water use efficiency and grower returns of drip irrigated native spearmint and four subsurface drip irrigated hop cultivars: Mt. Hood, Columbus, Chinook and Willamette. For native spearmint, stress levels were applied at different times during the growing periods. For hops, each stress level was applied throughout the growing season. The field experiments were carried out for two years at the Washington State University Irrigated Agriculture Research and Extension Center near Prosser WA.Mint results showed that biomass production decreased with increasing water stress as is expected. However, mint oil yield and quality were not significantly different across treatments. This suggests that deficit irrigating native spearmint might enhance oil accumulation. This is further supported by the observed increase in oil concentration as water stress increased. A number of mint production costs were affected by the reduction in applied water thus reducing the total mint production costs. Since oil yields were similar across treatments, revenues were not significantly affected. This resulted into increase in net farm income. Also, water stress improved the water use efficiency in native spearmint.Hop results showed that the dried hop cone yield decreased with increasing water stress in all the cultivars. The hop cone quality however did not change significantly across treatments. In the full year of production, water stress improved water use efficiency in hop production across all the cultivars. In the Yakima Valley, reduction in amount of water applied only affects the cost of pumping of the irrigation water which is minimal when compared to the total cost of producing hops. The yield reductions due to applying less water to hops caused reductions in revenues that were higher than the savings in the cost of producing hops due to pumping less water. This decreased the net farm income. The study observed how the subsurface drip irrigation system coupled with scientific irrigation scheduling can substantially reduce hop water use.This study also provides production functions for irrigation optimization of native spearmint and four hop cultivars

Response of drip-irrigated native spearmint to different water stress levels applied at different times

Response to water use challenges in irrigated agriculture

Effect of deficit irrigation on the cost of producing native spearmint oil in Washington state

Washington State is the largest producer of native spearmint oil in the U.S. This publication provides guidelines for assessing how deficit irrigation (deliberately irrigating a crop with less water than it would get if it were being fully irrigated) affects the cost of producing native spearmint oil in Washington State

Efficacy of boom systems in limiting runoff on center pivots

Center pivot and linear move irrigation systems’ design and operation are primarily limited by soil infiltration rates. Boom systems have been suggested to improve infiltration and decrease runoff by reducing the instantaneous water application rate of center pivots and linear move systems. In this research project, we compared runoff from plots irrigated with typical in line sprinklers on a linear move irrigation system with those irrigated with off set boom systems. In line drops consistently generated greater runoff than ‘the boom systems in all of the irrigation events. Differences in runoff between the drop types were significantly different for the second, third, fourth and fifth irrigation events. The runoff differences from in line drops ranged from 3% to 24% greater than the boom systems. Runoff as a percentage of irrigation water applied increased with each irrigation event on both drop types

Evaluating irrigation scheduling and application efficiency: baseline to revitalize Meki-Ziway irrigation scheme, Ethiopia

Irrigation scheduling and application efficiency were evaluated for Meki-Ziway irrigation scheme in an overall effort to revitalize the scheme. The evaluation was done on three furrows in each of the four farm plots. Field capacity, permanent wilting point and bulk density of the four plots were determined in the laboratory. We monitored furrow inflow rate, cutoff time and soil moisture content in the plots over a period of about 4 weeks. This monitoring was done during both periods of water availability and water scarcity. Our results show that on average 58% (range 42–77%) of the applied irrigation water in this scheme can be considered beneficial for crop growth. The results also show that soil moisture content at farm plots at the canal head sections was always between soil saturation level and permanent wilting point. For farm plots along the middle and tail sections of the main canal, soil water content would even fall below the permanent wilting point. This was caused by the absence of a water allocation system to ensure equity, and by large, channel seepage losses along the unlined main canal. To improve irrigation efficiency therefore, rehabilitation of the physical infrastructure of the scheme, more equitable irrigation water distribution in the scheme and improvement in on-farm irrigation water management are needed

A review of trends, constraints and opportunities of smallholder irrigation in East Africa

Smallholder irrigation expansion would signi cantly increase agricultural production, and reduce food insecurity and poverty levels in East Africa. This paper reviews literature on trends, constraints and opportunities of smallholder irrigation in four East African countries: Ethiopia, Kenya, Tanzania and Uganda. Irrigation development has been slow in these countries, and has been mainly through traditional schemes. Recently, individual irrigation technologies such as small motorized pumps, drip kits, treadle pumps, rope and washer pumpsarebeing promoted.Adoption ofthesetechnologiesandexpansion ofsmallholder irrigationhoweverface a number of challenges including land tenure issues; lack of access to appropriate irrigation technologies, improved agricultural inputs, reliable markets, nance and credit services, and research support; poor transport and communication infrastructures; poor irrigation water management; poor extension systems; and the over dependence on national governments, NGOs and donors for support. Despite these challenges, opportunities exist for smallholder irrigation expansion in East Africa. Such opportunities include: high untapped irrigation potential; rainwater harvesting to improve water availability; high commitment of national governments, NGOs and donors to smallholder irrigation expansion; low cost irrigation technologies adaptable to local conditions; traditional schemes rehabilitation;growing urbanization; and increaseduse ofmobilephones thatcanbeused to disseminate information

Assessment of irrigation water distribution using remotely sensed indicators: A case study of Doho Rice Irrigation Scheme, Uganda

The rising competition for scarce land and water resources and the need to satisfy the global food demand from an ever-growing population necessitates novel methods to monitor irrigation scheme performance for improved water use efficiency. The traditional methods employed in sub-Saharan Africa to assess irrigation performance are point-based, expensive, and time-consuming, making monitoring and evaluation of these capital-intensive projects difficult. This study aimed at employing satellite data with high spatial and temporal resolution in assessing the performance of Doho Rice Irrigation Scheme through estimations of actual evapotranspiration. Actual evapotranspiration (ETa) was modelled from Landsat 7 imagery using the surface energy balance system algorithm on five clear days between January and April 2020. Using equity and adequacy metrics, the derived ETa was used to assess the irrigation performance of the scheme. Results showed that the equity indicator was generally fair, with the coefficient of variation between 0.11 and 0.08, close to the 0.10 threshold implying irrigation water is fairly distributed within the scheme. The average adequacy was 0.87, above the 0.65 threshold, indicating adequate water supply throughout the scheme. The study's findings can be used in future research and benchmarking with other irrigation schemes to address the country's water resource management challenges