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Starking apple trees on M793 rootstocks were grown in a low phosphorus (P) soil treated prior to planting in 1982 with different rates of P (as superphosphate) and, commencing three years after planting, nitrogen (N) as limestone ammonium nitrate (LAN). The object was to improve vigour, yields, and ftuit quality. Trunk circumferences increased progressively with superphosphate application rates up to 4,730 kg/ha. Susceptibility to bitter pit also increased as did fruit size, and leaf P and magnesium (Mg) levels. Some improvements in colour were also apparent. Yields increased at superphosphate applications up to 2,240 kg/ha, but at 4,730 kg/ha were little different to the yields at 2,240 kg/ha. Leaf potassium (K) tended to decrease with increasing rate of applied superphosphate. The levels of Bray 2‐extractable P in the soil decreased with time. Reapplying superphosphate to the 0, 1,180, and 2,420 kg/ha treatments at the rate of 1,286 kg/ha in 1989 resulted in some of the differences between the ...

Open-pollinated ‘York Imperial’ apple (Malus domestica Borkh.) and Nemagard peach (Prunus persica (L.) Batsch) seedlings were grown in nutrient solution containing either NH4+ or NO3-. The solution contained 0 or 4 ppm A1 and the pH was maintained at 4.5 by frequent adjustment. Apple seedlings grew better, and growth was less affected by Al, when the N source was NH4+ rather than NO3-. Peach seedlings grew better when supplied with NO3-. The total quantity of Ca, Mg, K, P, Zn, Cu, Mn, and Fe taken up by both apple and peach seedlings was less in the presence of Al when N was supplied as NO3-. Nutrient uptake by seedlings receiving NH4+ was slightly less or not affected by the presence of Al. Uptake of Mn and Fe was greater in both species and K and P uptake greater in apples, whereas Ca uptake by peach seedlings was less in the presence of NH4+. Aluminum uptake and transport was lower with NH4+ than with NO3- as N source.

Open pollinated ‘York Imperial’ apple seedlings (Malus domestica Borkh) were grown in an acid soil at 2 liming rates or in nutrient solution with or without added aluminum, with either NH4+ or NH3- at various rates as N source. High and equal Ca levels were maintained for the different Al treatments. Growth of seedlings and Ca-uptake in the soil were much less at pH 4.7 than at 5.1, and seedlings responded better to liming when NH4+ was the N source. With either N source, best growth was obtained at a rate of 100 ppm N, whereas growth was lower at 50 and at 200 or 400 ppm N. In nutrient solution, the efficiency of Ca-uptake by roots and of Ca-transport was decreased by the presence of Al. This decrease was the greatest when NH3-, rather than NH4+, was the N source. The findings suggest interference by Al in nitrate metabolism. Al is toxic to apple seedlings at chemical activity in the order of 6.5 × 10—6M.

The role of mineral nutrition in the development of internal breakdown of plums was evaluated by applying various statistical models to data obtained in a field survey. All techniques cont...