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Broccoli (Brassica oleracea L. var. italica) head weights and yields are highly sensitive to plant densities (P) and rectangularity. Broccoli cultivars were grown at four plant spacings (2.2 to 8.6 plants/m2) and four N rates (O to 336 kg N/ha) in 1986 and 1987. In 1988, plug spacings, as above, were factorially combined with treatments of one, two, or three plants per plug. Head weight (w) data were fitted to the reciprocal model: 1/w = a + bp and the exponential model: w = AKP, where a, b, A, and K are constants. Nitrogen rate did not interact with p. In 1986 and 1987, both the reciprocal and exponential models fit the w data (expressed as w relative to wmax for each cultivar) with highly significant R 2 values of 0.525 to 0.605. Yield equations derived from these models were asymptotic. In 1988, clumping (multiple plants per plug) reduced head weights but interacted with plant density. Only the exponential model could account for the assumption that clumping effects diminish as plant densities increase; the reciprocal model predicted the opposite effect. The exponential model was expanded to the form: w = CAKP, where C is proportionate reduction of w due to clumping. Derived yield models were asymptotic for the reciprocal model and parabolic for the exponential model.
Abstract
Flowering, fruit set, fruit size, and bearing potential are the main components of tree fruit and nut yield. The contributions of the individual components to yield and their interrelationships must be clearly defined in research addressing tree fruit productivity. Researchers have been inconsistent in terminology and procedures used to evaluate treatment effects on the major yield components. Although the relative effect of a treatment may be evident within an individual study, standardized measuring and reporting procedures are necessary if one wishes to compare results within the same species from various investigators, locations, and disciplines.
Abstract
A pre- or postharvest foliar B application was found to increase fruit set of ‘Italian’ prune (Prunus domestica L.). A prebloom B spray failed to increase set. Neither fall nor spring applications influenced the amount of fruit lost in the midsummer or “blue” drop. All trees involved in the experiment had adequate B by the standard index of tree nutrition, August mid-shoot leaf analysis. Incipient B deficiency did not appear to be involved.
Fall foliar B increased B levels in dormant bud and spur tissues and in flower buds and flowers. A prebloom B spray increased B levels of floral tissues to a lesser degree. The highest B concentration was found in the ovary. Boron concentration in flower buds in April following a fall B spray was as much as five times the amount found in mid-shoot leaves in August. August mid-shoot leaf analysis revealed higher levels in leaves from trees treated the previous fall in only one of the 2 years.
Several morphological and physiological effects of the fall B spray were observed. Among these were a slight delay in the time of bud break, a decrease in the size of flower buds and mature flowers accompanied by reduction of style and pedicel length, and a decrease in pollen germinability. B level of pistil and pollen had no effect on in vivo pollen tube growth rate.