Effects of sowing date, radiation and nitrogen nutrition on growth pattern and yield of lettuce (Lactuca sativa L.) crop

摘要

The effect of light radiation and temperature on growth patterns of a leafy lettuce cultivar and their interaction with fertilisation were evaluated by carrying out trials which combined three shade levels (65 percent, 35 percent y 0 percent) with three fertilisation rates (0, 75 and 150 kg N.ha~(-1)) in a winter sowing date. The same fertilisation rates were applied to an unshaded crop sown in spring. Growth rate, yield and quality traits of lettuce were measured. The results showed that the radiation level was the most important factor controlling growth in lettuce crops whereas the effect of N fertilisation was only observed in those treatments in which light intensity was not a limiting factor. Our results also indicated that N fertilisation rates higher than 75 kg N.ha~(-1) do not provide any significant benefit to leafy lettuce crops under open field conditions neither in winter nor in spring sowing dates.