Design, construction, and calibration of a weighable lysimeter for measuring water requirements of field crops for data-scarce areas of Ethiopia.

A simple weighable lysimeter was designed, constructed, and calibrated for measuring the water requirements and crop coefficients of shallow-rooted crops. It has a portable weighing mechanism to quantify changes in soil moisture content. The weighing mechanism consists of a horizontal steel bar, a hydraulic car jack, both ends hooked vertical steel bars, a stand, and a digital weighing balance. As the lysimeter's inner tank, a plastic drum with a 55 cm diameter that yields 0.24 m2 of internal area was used. A performance test was conducted, and a rating curve was developed at the beginning of the growing seasons in 2023 and 2024 to evaluate the sensitivity of the weighing mechanism in determining crop water use. Linearity, repeatability, and measurement uncertainty tests were conducted. The linearity error was ±0.04 kg and ±0.03 kg for the years 2023 and 2024, respectively, which is within the allowable limit. The weighing system repeats the measurement perfectly with no error (repeatability error was zero). The combined uncertainty of the measurements was 0.023 kg, representing the cumulative effect of individual errors. The lysimeter weighing system is capable of detecting variations in mass as small as 0.2 mm of moisture content. Therefore, the developed lysimeter can be used to determine water requirements and crop coefficients of shallow-rooted crops for the design and management of irrigation in data-scarce areas of Ethiopia.

Investigation of Bamboo Fibrous Tensile Strength Using Modified Weibull Distribution.

Ethiopia has a large coverage of bamboo plants that are used for furniture making and house building. So far, researchers have not studied the strength of Ethiopian bamboo fibers, which are utilized for composite applications. The current study measured the strength of bamboo fibers based on various testing lengths and calculated the predictive tensile strength using a modified Weibull distribution. Moreover, the quality of the extraction machine is evaluated based on shape and sensitivity parameters. This research paper incorporates the coefficient of variation of the fiber diameters, considering the defects distribution through the length for measuring the predictive strength of the fibers. The fiber diameters were calculated using the area weight methods, which had its density measured using a Pycnometer. It has been examined that as the testing gauge length and coefficient variation of fiber diameter simultaneously increased, the tensile strength of the bamboo fibers decreased. The shape parameter, sensitivity parameter, and characteristic strength of Injibara bamboo (Y. alpina) are 6.02-7.83, 0.63, and 459-642 MPa, whereas Kombolcha bamboo (B. oldhamii) are 5.87-10.21, 0.33, and 408-638 MPa, as well as Mekaneselam bamboo (Y. alpina) are 5.86-9.63, 0.33 and 488-597 MPa, respectively.