Effect of sowing date and plant density on yield and yield components in the faba bean

Abstract

Faba bean cv. Fiord was sown at 3-week intervals between 24 April and 26 June at 6 densities varying from 20 to 56 plants/m². Days to emergence, flowering, pod set, and maturity were determined. At harvest, the biomass, yield, pod number, seeds per pod, and weight per seed were evaluated per unit area and the distribution of the yield components was evaluated for each node of the main stem.

Later sowing had little effect on the number of days to the appearance of the first pod but it progressively reduced the duration of the pod development period from 98 to 60 days. The biomass at maturity of the plants sown on 24 April was constant across all densities, at about 13·5 t/ha. Yield, however, decreased linearly with density from 6·7 to 5·2 t/ha. Harvest index, therefore, also fell with density. With later sowing, biomass and yield increased with density. The increase in yield was not as great; so again harvest index fell with density. Later sowing resulted in much lower yields and even at the highest density only reached 5·2 t/ha. Variation in yield was largely determined by variation in the number of pods per unit area. Seeds per pod was constant across the treatments but weight per seed decreased if sowing was delayed beyond 10 June.

With later sowing, the number of pod-bearing nodes on the main stems declined from 27 to 15. Early-sown plants at high density had fewer pods per node at the lower nodes and more pods per node at the higher nodes than plants at low density. This interaction was not evident at the second sowing and the number of pods at each node was unaffected by density. For the sowings in June, all nodes of the low density plants bore more pods

The number of seeds per pod was smaller at the lowest and highest nodes, but as there were so few pods at these nodes, this did not affect the mean number of seeds per pod when evaluated for all pods on a plant. Weight per seed was more uniform for the nodes of the early-sown plants than for those of the plants sown later, in which there was a marked decrease in weight per seed at the upper nodes