The response of green and seed peas to seeding rates and irrigation

The importance of the pea processing industry in Canterbury has over recent years increased considerably and the potential for further increases is high (White, 1968). A major problem at present though, is the low and variable yields being obtained. Pea crops for processing are usually sown at rates of around 270 kg/ha in 15-18 cm rows, resulting in crop densities of 80-90 plants/m² and average yields of 3900 kg/ha. During the seasons of 1969/70 and 1970/71, pea trials involving plant densities and irrigation were conducted by the Plant Science Department at Lincoln College in an endeavour to try and obtain information which could lead to the improvement of pea yields on an agronomic basis. (Anderson, 1971, White and Anderson, 1971) A range of plant densities was studied (52, 90, 105, 182 and 348 plants/ m²) with 182 plants/m² in a 10 x 5 cm spatial arrangement proving to be the optimum plant density for maximum yields of green peas. Based on this information, a further trial was established in the 1971/72 season to investigate the effects of five seeding rates and resultant plant densities on yield, using a row of 15.5 cm for all plant densities involved. It was hoped that from such studies practical optimum seeding rates could be determined for both the green seed pea stages under dryland and irrigated conditions. Water stress, a frequent problem in the sub-humid areas of Canterbury, has been a major limiting factor in achieving high pea yields. Yield responses to irrigation are common and during the 1970/72 season Anderson (1971) measured 57% response in yield to irrigation at the flowering and pod swelling stages of growth. The trial conducted in the 1971/72 season was designed to further study the benefits of irrigation, the timing of applications and the quantities of water required