WITH 3 PLATES SummaryCultivating grassland changes the physical state of the soil. The paper describes observations and measurements made in the field and the laboratory on a wide range of soils (with series names) in England over a period of 25 years. D y Journal of Soil Science, Vol. 23, No. 4, 1972 6113.5.3 c c 364 A. J. LOW All single-property measurements give only a limited assessment of the physical state of a soil. Soils can be assessed satisfactorily only by making a range of measurements appropriate to the farming system.

WITH FOUR PLATES Summary* It is not suggested that this 'ideal' condition is possible in practice. 60A. J. LOW * This work was done before the change to 2-and o.g-mm. sieves. 70A. J. LOW is used in addition. In Fig. 3 the percentage water-stable aggregates > 2 mm. and > 0-5 mm. are plotted. For the old pasture the two graphs are very similar. For the ley the slope is a little steeper on the 0.5-mm. graph. Nevertheless the difference is about the same between 2-mm. and o-s-mm. values at the last reading for both soils.

No abstract

SUMMARYThe composition of the leachate from undisturbed monolith lysimeters cropped with white clover or meadow fescue or maintained bare was compared with t h a t of the rain falling on rhein. No nitrogen fertilizer was applied only an initial dressing of phosphorus and potassium. The grass received rauch more nitrogen from the rain than it lost by leaching whereas the clover lost more t h a n it received. Most of the leached Ilitrogen was N O s -N -92 per cent on the bare soil and 90 per cent on the clover. A b o u t 271b nitrogen per acre (30 kg/ha) per year was drained from the actively growing clover sward risilig to about 1171b N/acre/year (131 kg/ha) when the clover died or was removed. Only 2.31b/ac (2.5 kg/ha) was drained from the actively growing grass sward. I t was estimated t h a t the clover fixed at least 2701b N/ac/year (303 kg/ha/year. The rates of leaching of potassium from a grass sward was about 1.7 lb/ac/year (1.9 kg/ha) and 0.8 lb (0.9 kg) phosphorus. The quantities were similar for clover. The grass received from the rain more phosphorus and potassium than was leached but only 60 per celit of the calcium and 13 per cent of the magnesium, similar results being obtained with white clover.During the year of establishment of the grass sward there was evidence of loss of gaseous nitrogen (elemental alid/or compoulld) from the soll: subsequently the nitrogen content of the soil slowly increased. Calcium loss from the bare soil with all average rainfall of 26" (650 mm) was about 100 Ib Ca/ac/year ( 112 kg/ha).

Grassland in the drier parts of England frequently suffers from drought in the summer months, but it is rarely irrigated and there has been little experimental evidence to show either when to irrigate or how much water to apply. Technical data on both points and on the effects of irrigation and nitrogen treatments on the yield and composition of leys are provided by the trials described here, though the practical aspects are not considered.

Summary An investigation was made of the time taken by a ley to change the physical state of an old arable soil ro that of an old grassland soil so that, for example, its physical condition on ploughing is the same as that of old grassland on ploughing. The process was found to be slow, taking possibly 50 years or more on some clay soils. On coarse sandy soils the process may be considerably faster, e.g. 5–10 years.

In many parts of the world crops can only be grown if the land is irrigated. Whilst this is not true of Britain, there are areas, south-east England in particular, where plant growth is limited by lack of water. The effect is particularly noticed on pastures.From the time of its establishment in 1928, Jealott's Hill (mean rainfall 25-7 in.) has been concerned with obtaining the maximum production from grassland. This involved not only trying to increase the over-all yield, but attempting to maintain as constant a rate of growth as possible during the summer months and thus overcoming the midsummer decline which normally follows the spring flush. It was soon apparent that the maximum response to fertilizers could not be obtained if the water supply was inadequate.Greenhill (1935) set out to find what is an adequate rainfall to maintain uniform growth under Jealott's Hill conditions. His approach was largely empirical. In a replicated plot trial, he supplemented, by watering one day each week, the natural rainfall, provided it had not reached one of the predetermined levels in the previous week (0-69and0-84 in.).In a year in which the spring and summer rainfall was above average he increased the yield by about 20 % for the lower ' rainfall' and 36 % for the higher.

Beauveria and Metarhizium spp. are currently under development around the world as biocontrol agents for a variety of pest insects. Use of these fungi in practical biocontrol programmes will require production of large amounts of inoculum. Although production techniques on solid substrates have been developed overseas, the production characteristics of New Zealand strains were unknown. The effects of solid media (rice, wheat and barley) with additives (glucose and yeast extract), temperature and length of incubation on conidial production were investigated. Maximum conidial yields achieved were 4.38 x 10 9 conidia/g rice for B. bassiana, 3.02 x 10 9 conidia/g dry substrate for B. brongniartii, and 1.42 x 10 9 conidia/g dry substrate for M. anisopliae. In all cases, maximum yield was achieved when fungi were grown on rice for 3 weeks at 23°C, under natural daylight.