PREDICTING THE BEST TIME TO APPLY NITROGEN TO GRASSLAND IN SPRING

A great number of experiments with varying dates of N application to grassland showed that the most suitable time of applying spring N in tbe Netberlaods varies, as a result of weather conditions, from year to year from mid-February to mid-April. In such experiments the best time of spring N application, which needs to be known in advance, can only be determined after the grass bas been harvested and weighed. The results of these experiments supported the opinion that the best application date coincides with the banging of grass growth. However, at that time it was not possible clearly to define the begimiing of grass growth. When in 1959 a measuring disc was put into use the beginning of grass growth could be precisely determined and it was then found that the beginning of grass growth was closely correlated to a certain accumulated temperature from 1 Jan. from which the date of the beginning of grass growth can be predicted. This date is the most suitable one for applying spring N to grassland.     

THE EFFECTS OF SHOOT REMOVAL ON THE RHIZOME CARBOHYDRATE RESERVES OF COUCH GRASS (AGROPYRON REPENS (L.) BEAUV.)

Summary. Three box experiments examining the effects of shoot removal on rhizome carbohydrate reserves are reported.
During summer in England the optimum frequency of hand defoliation for maximum loss of carbohydrate was 10–14 days. As in previous experiments, high levels of soil nitrogen sometimes increased the rate of carbohydrate loss from 9-in. rhizome pieces. This result was obtained when nitrogen was supplied as a nitrate, an ammonium salt, or urea.
Repeated applications of 2 or 4 oz/ac paraquat over a period of about 60 days reduced carbohydrate reserves to about 50% of the level obtained with the same number of hand clippings. It is suggested that paraquat may have been translocated to the rhizomes, the carbohydrate content of which may have been reduced by an effect of the paraquat on the respiration rate.
When plants which had been subjected to different methods and frequencies of defoliation were uprooted and buried beneath 2 in. of soil, there was a connection between the rhizome carbohydrate content at the time of burial, the ability of the plants to regenerate, and the rate at which new carbohydrate reserves built up during the following two months.     

Aus der Preu?ischen Staatsforstverwaltung

Ohne Zusammenfassung     

Effect of the Time of Application of Fertilizer Nitrogen on the Growth,Flowering and Fruiting of Maiden Apple Trees Grown in Sand Culture

Mailing II rootstocks were grown throughout 1960 in sand on nutrient culture solutions containing 1, 4 or 10 mg. equivalents of nitrogen as nitrate (referred to as N₄, N₁₀ rootstocks) and during that summer each rootstock was budded with the variety Lord Lamboume. The growth, flowering and fruiting performance of the resultant maiden shoots were recorded from bud break 1961 to fruit set 1962. Throughout this second period each tree was given only a minimum of nitrogen (N_x) except during a certain period of one or two months’ duration, when it received a simulated fertilizer application (N₁₀).

The greatest amount of primary extension growth in 1961 took place on the maidens given supplementary nitrogen in June on the N₁ and N₄ rootstocks and in July on the N₁₀. Secondary extension growth in 1961 was apparently induced by supplementary nitrogen given to the maidens on the N4 stocks in July and to those on the N_x in August.

The highest number of fruit buds and blossoms in 1962 resulted from the June 1961 high-nitrogen supplement to the maidens on the N_r and N₄ stocks and from the July supplement to the N₁₀.

After open pollination, the maidens grown on the NIO stocks set fruit better than on those that were more nitrogen-deficient. Among the N₁₀ and N₊ maidens, those receiving the September nitrogen supplement gave the highest yield.

These results are discussed especially in relation to apparent differences in quantity and quality of blossoms. It is suggested that the quantity of blossoms is related to the amount of primary extension growth, while the quality is determined by the extent to which reserves of carbohydrate and nitrogen have been accumulated during the previous autumn.     

Growth Regulator Effects on Quality and Pre-Harvest Drop of Worcester Pearmain Apples

The application of 2-chloroethylphosphonic acid (CEPA) at 750 or 1500 ppm improved the colour of early harvested Worcester Pearmain apples but greatly increased pre-harvest drop. The drop-promoting effect of CEPA could be overcome by applying succinic acid 2,2-dimethyl hydrazide (aminozide) at 2000 ppm or a-(2,4,5-trichlorophenoxy)-propionic acid (2,4,5-TP) at 20 ppm. The combination of CEPA 750 ppm+2,4,5-TP 20 ppm appeared to be particularly promising for improving the attractiveness, flavour and texture of Worcester Pearmain picked on 1st September and 7th September. No damage was seen on the trees either in the year of application or the following year.