Inorganic Plant Nutrients Research Articles

Concentrations of some inorganic plant nutrients in saline lakes on the Yorke Peninsula, South Australia

The concentrations of major ions (Na+, K+, Ca2+, Mg2+, Cl-, SO42- and HCO3- + CO32-) and minor ions (NO2, NO3-, NH4 and PO43-) were determined in 10 saline and mostly ephemeral lakes on the Yorke Peninsula, S.A., over a range of salinity (27-250 g/l). The major ion dominances were similar to those of saline lakes elsewhere in southern Australia: Na+> Mg2+ > Ca2+ > K+ : Cl- > SO42- > HCO3- + CO32-. Concentration ranges of minor ions were wide; individual concentrations of ions were not correlated with salinity, but in the least-saline lakes (salinity < 150 g/l) phosphorus appears to be the most likely limiting plant nutrient, whereas in the more saline lakes (>150 g/l) nitrogen appears to be so.

Mineral and Chemical Alluviation in a Unique Pedologic Example

ABSTRACT Flood water from the Snoqualmie River and Cherry Creek, laden with fine silt, colloidal clay, and dissolved ions, stands quietly part of each winter season over land underlain by an old peat bog near Duvall, Washington. This water, instead of leaching and abstracting inorganic plant nutrients as is the usual role of surface water and soil, donates to the soil dissolved ions, colloidal material, and fine-grained, partially decomposed rock fragments (naturally pulverized agstone). Analyses are presented which indicate the annual contribution of the alluviation. In the chemical weathering of rocks to soil the sequence of energy effects begins first with the disruption of relatively strong crystal bonds between ions, thereby making the ions vulnerable to pick up by plants by way of the exchange bonding energy of rootlets. As weathering advances, however, and abstraction of ions from the rocks by leaching continues, the concentration (activities) of available nutrient ions in the soil decreases, and their energies of exchange from soil clay rises above the energy of the rootlets to pull them away. Thus, weathering at this later stage is destructive to soil. Agriculture, therefore, operates most efficiently on soil in which the rocks are in a stage of partial or intermediate decomposition. Economic geologists interested in the sources, use, and production of agstone may apply in practice the principles which may be deduced from this example in nature.

The Measurement of Primary Production1

A discussion is presented of the measurement of primary production by short‐term experimental methods and by measurement of in situ environmental changes occurring over longer periods of time. The methods described include the measurement of photosynthesis by oxygen production, carbon dioxide assimilation and the associated pH change, and uptake of radioactive carbon (C14). In situ changes in the standing crop and the concentration of inorganic plant nutrients are also discussed, and the possibility explored of relating the rate of uptake of radioactive inorganic tracers to primary production. The relationship between chlorophyll and photosynthesis is reviewed and some new experimental evidence is presented which indicates the possibility of using chlorophyll concentration as an index of primary production. In the discussions of each method emphasis is placed on sensitivity, reliability, and the interpretation of the data.