The economics of mechanical versus chemical weed control in peas and lettuce under different tillage systems and irrigation regimes

A study was conducted to compare the economics of four systems of weed mana gement under three irrigation regimes and tillage systems. The effects of w eed management system and irrigation regime and their interactions on peas and lettuce yields were investigated. The research project utilized a facto rial design with type of weed management system crossed with irrigation reg ime and tillage system. The four weed management systems were chemical herb icides only, chemical herbicides and mechanical cultivation, mulch control and mechanical cultivation and mechanical cultivation only. The three irrig ation regimes were 25% of the crop water requirements, 50% of the crop wate r requirements and 100% of the crop water requirements. The three tillage s ystems were chisel ploughing as primary tillage followed by disc harrow as secondary tillage, mouldboard ploughing as primary tillage followed by rota ry tiller as secondary tillage and zero tillage. The average pea and lettuc e yields for 2 years for each of the four weed management systems at the th ree irrigation regimes and tillage systems were analysed and reported. Mach ine and chemical costs were calculated by using current list prices of mach inery and actual costs of chemicals. Based on results from field tests, it was found that weed management method affected pea and lettuce yields. Mech anical cultivation between the rows and using plastic mulch to cover the ro ws gave the highest pea and lettuce yields. Tillage system also affected yi elds of the two crops. It was found that zero tillage produced higher yield s than chisel and mouldboard tillage systems. Percentage increases in yield between 8 and 31% were obtained with zero tillage treatments compared to t he other two tillage systems. Irrigation regime significantly affected pea and lettuce yields. The irrigation regime (100% of the plant requirement) p roduced the highest yields. The results of this analysis showed that mechan ical weed control with zero tillage practice was the alternative with the l owest machinery investment and total machinery and labour costs per hectare per year, followed by chisel tillage and finally mouldboard tillage. (C) 2 001 Silsoe Research Institute.