Trials were carried out to ascertain which of four systemic insecticide/nematicides were absorbed by young coconut palms (Cocos nucifera L.) using three different methods of application. Stem injection of Bidrin and Nemacur are impractical because the chemicals break down too quickly and frequent retreatment would result in too much physical damage to the young trees. Lannate was not absorbed from leaf axil placement, and broke down too quickly when absorbed from the soil to be of practical use. Nemacur was not absorbed through the leaf axil, but was from the soil and lasted up to 14 weeks in the plant. Temik, absorbed both through the leaf axil and from the soil, lasted up to 14 weeks. The possibility of controlling red ring disease of coconuts with Nemacur or Temik is considered.

Among the processes in orchard fruit production, partial mechanization has done little to reduce the peak demand for labour during the year. The most welcome new machine would be a harvester which, if it is to displace labour, will above all have to be efficient in not damaging the fruit. As regards English apples and pears, a machine that is to replace labour that is no longer available would have to be almost equally efficient. Working back from an economic specification, it seems that an efficient machine will be expensive, and that an expensive machine will have to harvest hundreds of acres to be economic.

Evolutionary studies in the cottons began with the demonstration by Harland that true cottons could be divided into four genetically distinct species, each carrying an internally balanced genotype that was disrupted in crosses with any other. Harland's genetic classification has stood the test of time, and contributes substantially to our understanding of speciation in other genera, as for example, Phaseolus. In addition, it provides a genetic basis for the observations described by Anderson as ‘introgression’.

Studies of cottons found growing wild, and of their relationship to cultivars in the same areas, led to the hypothesis that all true cottons are cultivars, and those now found wild are escapes. This hypothesis, though it led to purposeful exploration of the distribution and relationships of the cottons, was found to be inadequate. A new approach to the relationships of the cottons became possible following Thoday's demonstration of ‘disruptive selection’ in Drosophila. The disruptive situation has been shown to obtain as between cultivars and their wild relatives in Sorghum and in a number of other crop plants.

Consideration of the time scale of agricultural evolution makes it clear that the recent origin theory is untenable, and a review of the status of the ‘wild’ cottons shows that they are adequately accounted for as weedy relatives of the cultivars, descended from common wild ancestors under disruptive selection.

It is concluded that crop plant evolution has gone on very largely within the balanced gene pools which Harland regarded as genetic species.

Trials were conducted for three seasons at a range of altitudes in Tanzania to investigate the effect of plant populations and levels of applied nitrogen and phosphate on the performance of maize varieties. Increasing population to 47,500 plants per hectare gave increased yields even though cob size and number of cobs per 100 plants showed considerable reductions, but 72,000 plants/ha. is probably too many for late maturing varieties. Sites over 900 m. showed good response to applied fertilizer, but below 900 m. response was much smaller or absent. Cob height was increased by fertilizer but hardly affected by spacing, no treatment made any appreciable difference to days to 50 per cent pollen shed, and lodging increased with closer spacing.

Root and sugar yield responses of the Polyrave variety were more favourable to the lower of two population levels (70,000 and 92,000 beets/ha.) and to the wider of two between-row distances (60 and 50 cm.). When the triploid Trirave variety was space planted and, for comparison, conventionally planted and thinned to 3 population levels at 60 cm. between-row distance, the intermediate (87,000 beets/ha.) level gave the highest sugar yield. The thinned treatments consistently outyielded the corresponding space-planted treatments. Space planting at 40 cm. between-row distance resulted in high beet populations (130,000 beets/ha.) which evoked unfavourable responses in root and sugar yield and even in sugar content.

An appreciable loss of gaseous N from added urea was recorded in two sub-tropical soils of East Pakistan under laboratory controlled conditions, markedly accentuated by the presence of decomposable organic materials which increased ammonification and tended to decrease nitrate accumulation. The addition of bonemeal to the soils had little effect.

When wetted overnight by dew, dye spots on a cone-shaped paper ‘sensor’ will spread to an extent which depends on both the duration and the intensity of dewfall. Results from such a sensor have been compared with those from the de Wit recorder. Although only a qualitative assessment of surface wetness is obtained, the paper sensors are cheap and easily replicated, they can be stored for assessment later and they can be made in sizes to suit any particular situation in the field.

The responses of sprayed and unsprayed cotton to ammonium sulphate and single superphosphate at o, 125, and 250 kg./ha. were tested between 1959 and 1964, in three zones of Nigeria. Seed cotton yields of sprayed trials with both fertilizers at 0 and 250 kg./ha. averaged 534 and 768 kg. ha.−1 respectively with significant and positive linear response components in all zones, but significant negative quadratic responses to phosphate in the north and to nitrogen in the south, with a significant interaction in the south. Seed cotton yields of unsprayed trials with both fertilizers at 0 and 250 kg./ha. averaged 305 and 384 kg./ha. respectively with significant positive linear responses to phosphate in the north, to nitrogen in the south and to both in the east and no interactions.

Effects of moisture stress during different stages of cotton development were examined in two experiments when temperatures were mild and evapotranspiration less than 6 mm./day. Two varieties of upland cotton, Acala 4–42 and Deltapine Smoothleaf, were affected similarly. Moisture stress at the beginning of flowering reduced growth rate and the numbers of flowers and bolls. During the second half of the flowering period it reduced the percentage of boll retention, boll number, boll weight, seed index, lint index and lint length. Stress during boll development had similar effects and caused earlier maturity. Lint yield was reduced significantly by moisture stress during each of the periods but tensile strength of lint was not affected. Three irrigations, if properly timed so that no appreciable moisture stress occurred, were sufficient for high yields and good quality of lint, and the first could be postponed until after flowering began without any loss in yield.

The effects of moisture stress during various stages of the development of two varieties of upland cotton (Acala 4–42 and Deltapine Smoothleaf) were studied in two irrigation experiments in the Bet-She'an valley, where summer temperatures were high and evapotranspiration in the fully irrigated treatments was up to 8–10 mm./day in July and August. Optimum time for first irrigation in the Bet-She'an valley was two or three weeks before flowering and six or seven irrigations, if timed to prevent moisture stress, were sufficient to give high yields and good lint quality. Lint yield ranged from 270 kg./ha. in non-irrigated to 2000 kg./ha. in the fully irrigated treatments in 1966.

The shallot is a common crop in tropical areas where daylength and temperature conditions do not permit the growing of onions. Shallots are dormant for 70 days from the time of harvest to sprouting in bulbs stored at room temperature (75 to 95°F), during which period about 40 per cent of the bulbs are lost due to drying out and disease. Bulbs stored at lower temperatures (40 to 60°F) sprout more rapidly, with an optimum of about 50°F. Cool storage enables the farmer to use the previous season's crop for planting within 30 days of harvest.

Visual symptoms of deficiencies of manganese, copper, zinc, iron, molybdenum and boron on sisal are described, and compared with those observed previously with deficiencies of macronutrients. The diagnostic value of symptoms is discussed, and tentative suggestions made for micronutrient concentrations in leaves for adequacy and deficiency.

Linear regression of grain and straw yield of dwarf wheats on level of fertilizer nitrogen was significant, but the efficiency of fertilizer nitrogen was determined by the time and method of its application. A single application as a basal dressing was the least productive for grain yield, while split fertilization at sowing and at first irrigation increased the efficiency of applied nitrogen. Further splitting in three doses did not benefit wheat. Foliar application of nitrogen to replace top dressing at the heading stage was of no advantage while replacement of a top dressing at first irrigation by urea spray at heading was definitely deleterious.

Climatic conditions affecting the development of CBD are assessed by measuring wetness within the tree canopy and air temperature. Saturation of the tree canopy, necessary for spore dispersal, occurs most frequently at the tops of trees and the duration of wetness permitting spore germination is most prolonged at night. Night air temperatures are closest to berry temperatures and are important in assessing infection periods. Disease development in 1968 and 1969 was related to the number of infection periods during the growing season. Polythene tree covers which kept trees sufficiently dry to stop disease development were used in determining infection at different times of the year.

The effects of moisture stress at various stages of development were studied on two varieties of cotton in the arid Negev region of Israel. Experiments over two years indicated that the stage at which moisture stress occurred determined its effect: when at the beginning of flowering, yield was considerably reduced; at the peak of flowering there was a less pronounced effect; and when stress occurred during boll development it had an effect in only one year, when reserves of moisture in the deep soil layers were low. Lint yield ranged from 380 kg./ha. without irrigation to 2150 kg./ha. with five irrigations. Effects on lint length and lint strength were also studied. Two physiological indices, stomatal aperture and refractive index of leaf sap, were used to determine the onset of moisture stress.

Observations on the relative degree of root nodulation were made for three successive years on tall and short cultivars of Pisum sativum and Phaseolus vulgaris sown at dates appropriate to each cultivar and grown under conditions of ordinary horticultural practice. In P. sativum, it was found that the shorter the cultivar, the greater were the number and weight of nodules per plant and the weight of nodules as a percentage of plant weight; dwarf cultivars also produced a greater weight of nodules per square metre of ground occupied and per square metre per day of crop growth. In Ph. vulgaris, differences in number and weight of nodules per plant between dwarf and climbing cultivars were not consistent between years. In a single comparison between Ph. uulgaris and Ph. multiflorus (scarlet runner beans), numbers and weights of nodules per plant were almost identical. Some agronomic implications of these findings are discussed.

Crop Growth Rate, Leaf Area Index, Net Assimilation Rate and Harvest Index were estimated for oil palms in nine age groups growing on coastal alluvial soils in Malaysia. The mean Crop Growth Rate of mature palms was 29·83 t./ha./yr, with a Leaf Area Index of 3·61, and Net Assimilation Rate was 0·16 gm./dm.2/wk. Photosynthetic efficiency was about 2·2 per cent. Oil constituted about 17 per cent of total dry matter production. Possibilities for improving the yield of oil are briefly discussed.

Under the three levels of submergence (0, 5 and 10 cm. depths), water requirement of rice was maximum at 10 cm. but crop performance was similar to that at 5 cm. With medium and high levels of fertilization the crop had a higher water requirement than under low level, for ‘aus’ and ‘aman’ crops. Compacted soil compared well with puddled soil, but water requirement was appreciably higher with shallow puddling. In the two seasons water requirement, transpiration, evaporation and percolation losses were greater under submergence, and only transpiration was greater under higher levels of fertilization. Transpiration was maximum at flowering stage.

In 1968–9 and 1970–1 small-scale experiments were set up on over a hundred farms in Barbados, simple enough for farmers to carry out with a minimum of supervision. Results were obtained from more than 70 in each year. NK fertilizing gave no increase in yield in 1968–9, but a significant increase of 800 lb per acre in 1969–70. In each year NPK gave a highly significant increase of 1000 lb per acre. There was also a general increase in yield with increasing rainfall up to about 40 inches during the growing season and with closer than normal spacing especially under conditions of low rainfall. Planting later than usual led to marked decreases in yield.

The variation in number and yield of tubers from three commercial fields of sweet potato was measured over three seasons. Sources of variation were attributed to factors external to the plant, such as soil, management and climatic differences, and to inherent plant factors, including type of planting material. It is suggested that a reduction in variability could lead to increases in productivity, and may also increase the precision of field experimentation.