Spring wheat cv. Opal, Orca and Gaby, sown in 1967-8 on various dates at different seed rates or with different levels of N and chlormequat, were assessed for green area of leaves, internodes and ears. Green-area duration (D) for flag leaf and for peduncle were closely correlated with grain yield, the combined value for the 2 parameters accounting for 81 and 61% of the variance in grain yield in the 2 years, respectively. Including all the values of D in a multiple correlation increased the predictive value to 83 and 74%. D for ears was closely correlated with grain yield in 1968 only. The grain: leaf ratio was higher for Gaby than for the other 2 cv. (Abstract retrieved from CAB Abstracts by CABI’s permission)
As a result of an investigation into the causes of self-intolerance of rye (i.e. of rye following rye) it could be proved that a number of obvious well-known pathological agents such as nematodes, foot rots and phytotoxins cannot be accepted as important causes. Circumstantial evidence was produced strongly suggesting that the composition of the soil microflora (to a certain extent itself the result of growing this crop in the previous yr) is the main cause. Soil sterilization eliminates self-intolerance. One symptom of self-intolerance is the rapid degeneration of the root system at an early stage of growth. Application of larger rates of N postpones the onset of this phenomenon. The effect of N is indirect. A larger continued uptake of N furthers the potential for compensation of the plant. (Abstract retrieved from CAB Abstracts by CABI’s permission)
In an 18-yr rotational experiment on a light sandy soil, rye, grown after rye, showed a depression in grain yield of 30% and in straw yield of 10%, compared to rye following other crops (oats, maize, potatoes or rape). Investigation into the causes of this reduction in yield made it highly probable that neither nematodes nor foot-rot fungi were the main causes. Rye grown after rye seems to take up less N from the soil than in any other sequence.
ADDITIONAL ABSTRACT: In an 18-year rotational experiment on a light sandy soil in the Netherlands, yields of seed and of straw from rye following rye were reduced by 30% and 10% respectively, compared with yields from rye following other crops. Investigation showed that it is highly improbable that either nematodes or foot rot fungi are the causes. (Abstract retrieved from CAB Abstracts by CABI’s permission)
In long-term experiments with spring wheat, potatoes and sugar beet on ploughed or unploughed river clay soil, yield differences and differences in response to fertilizers were tentatively explained in terms of the limited size and activity of the root systems in the unploughed plots. CCT. (Abstract retrieved from CAB Abstracts by CABI’s permission)
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