S U M M A R YA key is presented to described stages of development of the pea (Pisum satioum). The aim was to produce a simple system to aid accuracy in communicating instructions for timing of field operations. The coded description is divided into four principal stages : germination and emergence, vegetative, reproductive and senescence. These are sub-divided into secondary stages. The practical use of the key is discussed with particular reference to the timing of application of agrochemicals.
Experiments to evaluate the optimum plant population density and
sowing date for winter peas,
semi-leafless cv. Rafale, were sited on free draining sandy loam soils
at Thornhaugh, Cambridgeshire in
1993/94 (Expt 1), 1994/95 (Expt 2) and 1995/96 (Expt 3). Peas
were sown at the end of October, in
mid-November and early December, at seed rates to achieve final plant densities
in spring of 50, 70
or 90 plants/m2. Seed rates were calculated allowing for
20% seedbed loss and plant loss due to
winter kill in Expt 1, and 15% in the other two years.Peas sown in warmer seedbeds in October emerged in early December or
before, November-sown
peas did not emerge until mid-January and December-sown peas from late
February to mid-March.
The growth stage of October-sown peas was thus more advanced than the later
sowings over the
winter and spring period. Winters were mild for Expts 1 and 2, but there
were more frost periods
during Expt 3.The yield of winter peas was dependent on sowing date. Yields of Rafale
sown in October were
highest in Expt 1, but lower than November-sown peas in 1995 (Expt 2),
as a result of damage from
late frosts during flower initiation in April, and in 1996 (Expt 3) due
to plant losses after a more severe
winter, frost periods and very cold winds in March. In Expts 1 and 2, yields
of December-sown peas
were significantly lower than November-sown peas, probably because they
were adversely affected by
drought stress during the sensitive flowering period. Therefore the optimum
time for sowing winter
pea cv. Rafale to achieve reliable yields appears to be mid-November. In
some years, however,
conditions may be too wet for late drilling, particularly on heavier soils.The highest plant population densities of 90 plants/m2
gave the highest yields in Expts 2 and 3, but
there was little increase between 75 and 90 plants/m2. Bearing
in mind financial return and seed costs,
the optimum target suggested is 75–80 plants/m2.
A key is presented to describe stages of development of the faba bean (Vicia faba), and is based on similar principles to the key for peas (Pisum sativum) (Knott, 1987). The coded description is divided into five principal stages; germination and emergence, vegetative, reproductive, pod senescence and stem senescence. These are sub-divided into secondary stages. The practical use of the key is discussed with reference to timing of crop husbandry operations.
Yield and yield components of three semi-leafless pea (Pisum satiuum) cultivars, of contrasting seed type/growth habit, were assessed at target planting densities of 40 -140 plants/m* on nine sites over three years. Flat-topped parabolic/asymptotic yield/density relationships were obtained. The plant density required to maximise (p max) and optimise (p opt) yield differed between cultivars: Helka, small blue, p max 126 plants/m2, p opt 101 plants/m* ; Solara, large blue, p max 124 plants/m2,p opt 94 plants/m2; and Countess, white-seeded, p max 104 plants/m*,p opt 71 plants/m*. Near-maximum yields were maintained between 70 and 140 plants/m* due to the ability of the pea crop to make compensatory increases in the number of pods per plant as density declined. Yield/density responses were influenced by site (e.g. soil type) more than by seasonal factors. The risk of yield reductions occurring at densities below 70 plants/m* was greater on a mineral soil than on a fertile organic soil. On the basis of agronomic and economic considerations, there was no evidence that target plant densities required to optimise yield should necessarily be higher for semi-leafless cultivars studied than for conventional leafed peas.
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