The response of field peas to plant intensity: A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Agricultural Science with Honours in the University of Canterbury

There has been several studies of plant population on the growth and yield of pea plants both in New Zealand and elsewhere. However, the majority of research has been centred on the production of peas for harvest in the green state. As a result, few trials have been extended to include the harvest of pea seed and even less have concentrated on crops grown solely for grain. It is generally agreed that pea crops saved for seed can be sown at lower rates than those grown for vining without any loss of yield. Sowing rates between 170 and 200 kg ha⁻¹ are frequently used in New Zealand for maple, blue and white peas which corresponds to plant populations of approximately 70 plants m⁻² . These rates appear to have been based on foreign practice with no known study of density effects on yield having been conducted in this country. However, most of the overseas work has been carried out in areas that differ in both climate and soils to the local environment. Extrapolation from this to our own environment therefore appears to have a fundamental weakness. Furthermore, the patently invalid practice of testing new cultivars of any crop at the current commercial density overlooks the possibility that variations in plant type may result in a better response at different densities (Donald and Hamblin 1976). There exists a need for evaluation of new cultivars at a range of plant population with the hope that optimal conditions for maximum exploitation of their unique characteristics can be defined. In light of the importance of the pea seed industry to New Zealand, especially in the multiplication of overseas seed lines, it was felt that an investigation of any adverse effects that sowing rate might have on quality of seed produced would be relevant both to this study and the industry as a whole. The present trial was therefore initiated to obtain information on the effect of seeding rate and resultant plant densities on yield and seed quality of field peas grown in Canterbury under dry land conditions