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Kiwifruit crop loading relationships published for pergola-trained vines in Hawkes Bay are shown to hold over a wider climatic range, several seasons and for T-bar training systems. Absorption of solar radiation by the vertical foliage ‘walls’ on the T-bar would reduce differences in total energy absorption between T-bar and pergola systems and contribute to the fact that training system was not, in itself, a significant determinant of yield. Relationships between harvest yield (Y) and fruit number (N) m−2 of orchard allocated per female vine, and mean fruit weight (μ) in g, can be described by: (1) Y=Y max ( N (N+K) ) and (2) Y= Nμ 1000 where K is a constant equal to 95.25 fruit m−2 of orchard and Ymax equals 13.48 kg m−2. After accounting for male vines, the latter figure corresponds to a maximum possible yield of 126 tonnes ha−1. Equation (1) expresses the potential productivity of kiwifruit, given currently available genetic material and good management. Combining eqns. (1) and (2) with a normal parameterisation of harvest fruit size distributions, allows returns from a range of crop loading regimes to be calculated directly. Using this approach, New Zealand grower returns (1986/1987 prices) are shown to be optimised for an average fruit weight of 90 g which corresponds to a crop load of approximately 50 fruit m−2. This information can be used by growers to develop pruning and thinning strategies that maximise returns rather than yield and also by industry to set price schedules that encourage the production of fruit in the most marketable size ranges.

An instrument designed for easy field measurements of kiwifruit volume or weight is described. Volume (or weight) calculated from a single length measurement has a resolution of ± 1 cm3 (g) permitting individual fruit growth to be monitored on a weekly basis. The assumption that the density of kiwifruit is 1 gm/cm3 is shown to be a very good approximation. Variations in fruit shape cause the average error in a single measurement to be 8%. Data collected are displayed with resolutions of 1 cm3 (g) for operator verification and are transferable to a portable personal computer to simplify data storage and analysis and to minimise handling errors. With this arrangement, a single operator can measure over 2 500 fruit in 4 h. The use of fruit growth information for assessing orchard practices such as irrigation management and for the early prediction of harvest fruit size in relation to target yield is discussed.

The transpiration of 2 kiwifruit vines grown within sheltered orchards in the Nelson locality was estimated in late summer by measuring their water uptake for 2 days following excision. Total daily transpiration by vines with vertically projected canopy areas of 16–17 m2 varied between 80 and 100 liters of water per day (4.8–6.1 mm/day) and ranged from 1.6 to 2.4 times the equilibrium evaporation rate. Stomatal conductances on excised vines were lower than those of adjacent uncut vines after the first day. Since transpiration estimates using the Penman-Monteith formula agreed well with the measured water uptake by cut vines, this equation was used to predict the transpiration of adjacent intact vines. Advective enhancement of evaporation contributed between 21 and 49% of the daytime water use despite the presence of multiple, closely spaced shelterbelts. Transpiration continued throughout the night as a consequence of incomplete stomatal closure, so that in total, advected energy was responsible ...

Losses of export-quality kiwifruit (Actinidia chinensis Planch.) attributable to wind damage increased with distance downwind of both natural and artificial windbreaks. These effects occurred on standard ‘T-bar’ trellised vines during a particularly windy season, within shelter spacings which the literature suggest should achieve adequate reductions in windspeed. Distance from the nearest upwind natural shelterbelt explained 57%of the variation in exportable yield per vine. Major losses resulted from frictional marks caused by fruit rubbing against each other and against plant canes. Mean proportions of exportable sized fruit rejected for this reason varied from 3–10%(for rows adjacent and to the lee of natural windbreaks) to 30–44%(3–4 rows downwind of artificial shelter). Trends in foliar damage and vegetative growth were similar to those observed in wind-rub damage. On rows partially shaded by natural shelter, up to 40%of the total fruit load did not reach export size because of poor pollinati...

The rooting patterns of mature kiwifruit (Actinidia chinensis Planch.) vines were observed in 2 soils of contrasting texture — Ohinepanea sand and Levin silt loam. Near the surface of both soils, roots extended laterally 2.2-2.4 m from the base of the stem. In the Bay of Plenty, rooting depths of 3 m have been observed and in the Ohinepanea sand significant moisture extraction occurred to depths exceeding 2.4 m. By contrast, the roots in the Levin soil were restricted to the top 70 cm because of unfavourable subsoil conditions. Some hydraulic characteristics of kiwifruit were measured and provided a basis for examining the relative contributions of plant and soilto- root resistances in the water uptake process. Large xylem vessels up to 0.5 mm in diameter in both roots and stem provide a very low resistance pathway for water movement within the vine. The measured hydraulic conductivities, which varied between 2.7 and 7.2 X 10-7 m2/Pa per s, may be the highest ever reported. Positive root pressure...

An important parameter necessary for describing the microclimate or heat budget at the earth's surface is the quantity of incident solar radiation. However, measurements of radiation on other than a horizontal surface are not normally available. This article provides a set of tables listing the ratio of total daily solar energy received on a surface of given aspect and slope to that received on a horizontal surface at latitude 37° 30' S. By multiplying this figure by the total short wave radiation recorded on a horizontal plane subject to similar cloud and atmospheric conditions, daily or monthly values of solar radiation on a sloping surface may be approximated.

The behaviour of 4-year-old kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang & A. R. Ferguson) vines growing in a Springbank soil within the Kerikeri Irrigation Scheme was monitored over the 1982–83 season. Water stress was induced in two vines by withholding irrigation and preventing rainfall recharge. Fruit volume expansion appeared strongly linked to the hydraulic status of the vines and could be described by a simple model whereby fruit either expand at the maximum rate shown on well-watered vines, or not at all if water is limiting. Volume losses resulting from fruit softening after extreme water stress were quickly recovered upon the reapplication of irrigation and could be ignored for modelling the influence of water stress on harvest yields. In the absence of rainfall or irrigation, the readily available moisture in this soil is capable of maintaining unrestricted fruit volume expansion for 10 days in mid summer. This result is extrapolated to other soils within the Irrigation Scheme...

The distribution of fruit weight at harvest from 0.5 ha blocks of kiwifruit in the Kerikeri district is shown to closely approximate a Normal distribution with a constant standard deviation of 20.5 g. The standard deviation changed less than 2 g between seasons despite wide variations in the mean fruit weight with crop loading and vine age. This Normal approximation provides a mathematically convenient assumption which should be considered when modelling the influence of management practices on yield or the effect of industry pricing schedules on grower returns.