Additional effects of fertilizing on several foliar nutrient concentrations and ratios inEucalyptus grandis
The interaction responses to N, P, K fertilizing and limimg in four experiments withEucalyptus grandis are described. Inclusion of the N—P and P—K relationships gives a clearer understanding of the nutrient requirements of this species. Phosphorus and nitrogen supply is of great importance, but must be well balanced when either or both are adequately supplied in specific circumstances. Potash supply is also of importance, especially in conjunction with phosphorus, although no direct benefit has been found in these experiments. Increased soil pH reduces the uptake of these latter two nutrients. Magnesium is of greater importance and more readily taken up than calcium inE. grandis. Zinc seems to be the most important of the micro-nutrients and its interactions make it evident that Zn-enriched fertilizers should be used. Manganese levels are generally high where growing conditions are adverse. The great importance is indicated of the foliar N/P and P/K ratios as diagnostic criteria for evaluating fertilizer needs inE. grandis.
The effects of fertilizing on the foliar nutrient concentrations inEucalyptus grandis
The foliar concentrations of macro- and micro-nutrients were studied in four N P K-lime fertilizer experiments withEucalyptus grandis, in the Natal Midlands and Zululand, South Africa. The sampling method and the chemical analysis of the foliar nutrient concentrations are described. Nutrient levels are similar to results found elsewhere and they differ little from those for other eucalypt species. There are many significant changes in foliar nutrient concentrations as a result of fertilizing. The relationship between soil and foliar N and P concentrations are clear as well as the importance of well-balanced N/P and Ca/Mg ratios. The Zn-P and Zn-Mg relationships make it apparent that Zn-enriched fertilizers should be used forE. grandis.
Soil‐Plant Relationships in a Eucalyptus Forest on the South Coast of New South Wales
The chemical and physical soil characteristics of the Eucalyptus associations in Benandra State Forest are described. Changes in species associations occur over a gradient of increasing moisture and nutrient status of soils from ridge to gully sites. Concentrations of major nutrients in leaves and bark of dominant trees on these sites generally follow the soil gradients. In particular, leaf phosphorus and bark calcium are correlated with the corresponding soil nutrients. Soil calcium and magnesium are also correlated with leaf phosphorus, indicating a possible interaction between these soil nutrients and phosphorus uptake by the trees. Soil magnesium is similarly correlated with bark calcium. Aluminum is the major exchangeable cation in soils of the poorer ridge sites which are the most acid. It is hypothesized that soil aluminum competes with other nutrient cations such as calcium and magnesium for sites of absorption on plant roots. In addition to the effect of soil pH on phosphate solubility, competiti...