Availability for ryegrass of cadmium and zinc from dressings of sewage sludge.

In pot trials, perennial ryegrass was grown in soil treated with sewage sludge containing 370 ppm Cd, 4940 ppm Zn and 450 ppm Pb or with equivalent amounts of Cd and Zn as sulphates. Levels of Cd and Zn in herbage in sewage sludge treatments were only about half as high as where the sulphates were used, and unlike in water culture did not increase progressively in subsequent cuts. (Abstract retrieved from CAB Abstracts by CABI’s permission

A plant test for sufficiency of phosphorus based on the phosphorus-nitrogen interaction in sunflower nutrition.

Sunflower plants were alternated between complete nutrient sol. and sol. devoid of either P or N. Successive harvests of top growth were analysed for P and N fractions to follow the time course of depletion and restoration. Under adequate P the TCA-insoluble protoplasmic substance contained 25 mol P/1000 mol N. Unrestrained incorporation of P needed the presence of at least 25 mol inorganic P/1000 mol protoplasmic N; P was adequate with at least 50 mol of total P/1000 mol N converted to proteins and nucleic acids. This ratio agreed with the ratio total P:total N at which max. growth was attained in published work of both field and pot experiments, presumably because most of the N was protein bound. Because of the possibility of higher contents of TCA-soluble N, it is better that total P be related to the TCA-insoluble N. (Abstract retrieved from CAB Abstracts by CABI’s permission

Nitrogen uptake by rice plants from a dry soil at maintained water supply from a greater depth.

In a pot trial in the Netherlands with sunflower and an upland rice cv., multiple-compartment systems with N and water supplied from different compartments were used to demonstrate that plant availability of N from a dry soil horizon was low. The separation of N and water in different soil horizons along with a decreasing input of irrigation water reduced the uptake of N more than the plant DM production was reduced by the decrease in the amount of water supplied to the plants. (Abstract retrieved from CAB Abstracts by CABI’s permission

Uptake of cadmium and zinc by ryegrass at high solution culture levels.

New top growth of ryegrass exposed to various solution culture levels of cadmium and zinc absorbed the elements without detectable interaction between the two. When after repeated clippings the contents had risen to 100 mg cadmium/kg DM or 700-1000 mg zinc/kg DM the new growth was injured. Interaction of zinc in cadmium toleration was suggested by the growth response but could not be established with certainty. (Abstract retrieved from CAB Abstracts by CABI’s permission

Tolerance of ryegrass to cadmium accumulation.

Freshly defoliated perennial ryegrass was transferred to nutrient solution containing Cd. Concentrations of 50-100 mg Cd/kg DM reduced top growth; in media rich in Cd (27 and 82 mg/l) the tops accumulated 100-500 mg Cd/kg DM during the first few regrowth periods, resulting in chlorosis, poor subsequent new growth and ultimately in the death of the plants. Because of the effects of Cd accumulation on subsequent growth and uptake, the level of tissue Cd toxic for plant performance and survival could not be precisely defined. Such levels would rarely if ever occur in contaminated pastures. (Abstract retrieved from CAB Abstracts by CABI’s permission