Characteristics of emitters under low pressure are essential for the design of low pressure drip irrigation systems. Few data is provided by the manufacturers for drip emitter operating under low pressures. No guidelines regarding the optimum combination of operating pressure head and lateral length available either. A laboratory test was conducted to evaluate the effects of pressure head and lateral length on water distribution uniformity of a PVC drip irrigation system. Five different lengths of lateral were considered under a pressure head of 55 kPa (8.21 psi / 5.6 m). The five lengths were 20, 40, 60, 80 and 100 m. Drip tape tested in this study is a non-pressure compensating (NPC) emiiter with 3.00 L/h discharge rate, 16 mm diameter and 35 cm emitter distance. Evaluation of 10 sampled emitters from the 20 m lateral showed a flow variation (Qvar) of 5%, uniformity coefficient (UC) of 99%, with a coefficient of variation (Cv) of 0.016. The 40 m lateral length showed a flow variation (Qvar) of 9%, UC of 98% with a Cv of 0.024. The 60 m lateral length also showed an average flow variation (Qvar) of 16%, UC of 95% with a Cv of 0.060. The 80 m lateral length showed a flow variation (Qvar) of 23%, UC of 93% with Cv of 0.08 and the 100 m lateral length showed a flow variation (Qvar) of 39%, UC of 89% with a Cv of 0.138. EU for 20, 40, 60, 80 and 100 m were 92, 90, 80, 75 and 58% respectively. Flow discharge vs. sampled emitter points (Q-E curves) was also developed for each length. Q-E curves were fitted to the data resulting in R 2 values of 0.1566, 0.1202, 0.8607, 0.7904 and 0.8998 respectively for 20, 40, 60, 80 and 100m. The operating pressure was 55 kPa (8.21 psi / 5.6 m) for all the tested length. From the statistical analysis, it was observed that as the lateral length increase invariably decreases the average discharge (Qvar). It is therefore recommended to use the 60 m lateral length with a low pressure head of 55 kPa (8.21 psi / 5.6 m), since the 60 m length satisfied the uniformity distribution criteria under a low pressure.

This study aimed to differentiate and identify the best soil field capacity for good plant growth and optimization of yield. Tomato is an herbaceous crop that needs an adequate amount of water for growth and yield optimization. This experiment was conducted in pots in a greenhouse to examine the effect of water stress on the growth, yield, and shelf-life of five tomato varieties namely Padma F1, Cobra F1, Symbal F1, Titanium F1 and Nkansah GH. This research was conducted at the project site of the NEIP Envirodome greenhouse at the Dawhenya irrigation scheme in Ghana, from January 2017 to May 2019 for 5 cropping cycles. The tomato varieties were subjected to soil field capacity of 80-100FC%, 70-75FC%, 60-65FC% and 50-55FC% with three replications in a randomized complete block design. Plant height, stem diameter, internode length, leaf relative water content, stomata conductance, transpiration rate, yield, and shelf-life were the parameters measured to compute the effect of water stress on the different tomato varieties. Results from this study revealed that water stress decreased significantly leaf relative water content, stomata conductance, and transpiration rate at p<0.05. In conclusion, moderate water stress at field capacity 60-65 FC% resulted in optimizing plant morphological characteristics, physiological response, yield, shelf-life, and total soluble salt.