Development And Performance Evaluation Of A Non-Weighing Lysimeter For African Spinach

ABSTRACT 

A non-weighing lysimeter was designed, fabricated, tested and installed at Arochukwu, Abia State, Nigeria, where the farmers who engage in dry season vegetable production do so with no knowledge of irrigation water requirements. This method tends to either over-irrigation or under-irrigation below the vegetable water requirements. Too much water can leach costly fertilizers to depths below the root zone, where both the water and fertilizer are permanently lost. Too little water causes the plant to wilt and dry, and sometimes salt accumulation. All these result in decreased yield. In order to provide efficient planning and use of available water, a non-weighing lysimeter was designed to determine the amount of water that could economically be utilized in growing crops. The materials used for the construction of the non-weighing lysimeter of 2.37m x 1.17m surface area with total depth of 0.6m, were locally sourced. Applying the water balance equation, the lysimeter was tested by using it to evaluate the crop evapotranspiration of African Spinach (Amaranthus Cruenthus). Irrigation was carried out by sprinkling through pressure generated by differences in head with the aid of a raised water storage tank. The flow rate was 0.38 L/s. The lysimeter was used to monitor irrigation water application, rainfall, drainage etc, and data generated were used to calculate crop evapotranspiration (ETc lysimeter). The climatic data collected during the period was used to evaluate the ETc using Blaney-Morin-Nigeria and Hargreaves-Samani methods. The ETc lysimeter, Etc Blaney-Morin-Nigeria and ETc Hargreaves-Samani were found to be 6.69mm-day, 5.07mm-day and 3.88mm-day respectively. Statistically, the difference between ETc lysimeter value obtained and ETc Blaney-Morin-Nigeria was quite insignificant, while that between ETc lysimeter and ETc Hargreaves-Samani methods were found to be statistically different at P>0.05 level of significance. While noticing that Blaney-Morin-Nigeria model is quite reliable in Evapotranspiration studies in Nigeria, the developed non-weighing lysimeter is said to be functional and efficient to use since the obtained ETc lysimeter fell within the acceptable ETc standard for African Spinach.