A relationship between grass N yield and total N supply was derived using data from experiments on grass-white clover swards. This relationship was very similar to that found previously using a larger pool of data from clover-free grass swards. The quantity of N released underground by the clover was estimated to be around 50% of the annual N yield in clover herbage. This is a much lower estimate than that reported by earlier workers.

The number of generations and the durations of the developmental stages of the codling moth (Cydia pomonella L.) that fed on fresh pear fruits were studied during a whole year, 1973, under laboratory conditions. In the next year, diapause of larvae was investigated in relation to the larval food.

Results showed that this insect reproduced four generations on pear fruits under laboratory conditions and diapaused during the whole period of the autumn. Broods of these generations occurred during April, June, July and September, respectively.

There was a suggestion that the larval food affected the induction of diapause in this insect. About 83% of larvae which fed on ‘ripe native Volos apples’ diapaused as early as the second half of June although the majority of larvae (93%) which fed on ‘immature pears’ continued development to adults and only 7% began to diapause under the same conditions. Up to 98% of larvae which fed on ‘fully mature ripe pears’ did not develop beyond the cocooning stage until the following spring, but 88% of larvae fed on immature pears stored at 4 °C for about 3 months reproduced a new generation about the end of October. These variable results should be attributed to the nourishment on different host-fruits in different maturity stages.

Data are reported from a 3-year study of the effects of date of planting on yield of overwintered onions. Delay in sowing from mid-August to late September increased plant losses during the winter and decreased yields of ware-size onions. Effects were most severe in early maturing varieties.

The authors regret the following error: On p. 53, equation (11) is incorrect and should read: