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A number of mass—diameter equations were compared for their potential use in indirect measurement of fruit masses of `Royal Gala' apple (Malus ×domestica). The fruit fresh-mass—diameter relationship changed with time during the season, hence no single function fitted the data well. Smooth piecewise functions that assume different relationships for intervening segments of a curve bounded by knots on the x-axis are particularly useful for modeling such data. The curve is said to be smooth because the first derivative of the function is continuous on the interval, including the knots. Two such equations, a three-parameter piecewise power function and a five-parameter spline exponential function, provided good fits to data. For both equations, the estimated mean bias on individual fruit predictions was within 5% of predicted mass over the two validating data sets. As for the precision conditional on no bias, a sample size of 20 fruit gave standard errors within 2.5% of mean predicted mass. These precisions are adequate to meet the industry requirements for monitoring fruit mass through the growing season. There was evidence of a seasonal difference in the estimated bias, but we were unable to confirm that this variation resulted from seasonal differences in fruit shape. Application of these two equations to data from other regions suggested that divergence from the estimated functional form may in fact be greater under increasingly different climatic conditions. Hence, further investigations to identify possible sources of these differences are necessary before the proposed equations can be applied across climatically different regions.

The influence of soil temperature during winter and early spring on subsequent budbreak and flowering of kiwifruit vines (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson 'Hayward') was studied at three sites during a 2-year period. Soil under kiwifruit vines was mulched for 28-day periods by laying sheets of clear polythene under vines. Mulching in June or July increased soil temperatures at 0.1 m depth by 1-2°C compared to control vines, whereas mulching in August and September elevated soil temperatures by 3-6°C. Increases in soil temperature were directly proportional to the amount of solar radiation incident on the orchard (r 2 =0.97). Mulching did not substantially alter the time of budbreak, the amount of budbreak, the rate of shoot growth, the number of flowers per shoot, or the number of flowers per winter bud. However, in one season the proportion of shoots that produced flowers was reduced when vines at the warmest site were mulched during late winter (August), but increased when vines at another warm site were mulched during early spring (September). These data suggest that the performance of kiwifruit vines is not very sensitive to soil temperature.

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