Four-year-old seedlings of twenty-eight hybrid progenies were infected with the Ghanaian swollen-shoot virus strain A, but all were too severely affected to be of practical value in combating the disease. Sensitivity was assessed by comparison with uninoculated controls; reduction in crop and in growth and deterioration of canopy were correlated. The Amelonado × Amazon crosses were no more sensitive than the better inter-Amazon progenies. The rapid decline of the infected trees may have been partly due to infection coinciding with the slowing down of vegetative growth as cropping commenced.

Experimental Agriculture, vol. 17, page 294:

Intensive Forage Production in Northern Mexico. I. Responses of Italian Ryegrass to Nitrogen and Irrigation

By N. Thomas and J. M. Farias

The following correction should be made to Table 2:

Item 11, column 4, should read 2598 and not 9598.

Unpublished, or not easily accessible, details are presented on the establishment of the agrometeorological network in Uganda and the collection, analysis and publication of the observations. Some of the agrometeorological research methods commonly used in Uganda are summarized.

An investigation was carried out in 1964 to determine the effect of seed size on oil content and seedling emergence in safflower (Carthamus tinctorius L.). Small, medium and large seeds yielded 37·0, 36·6 and 35·7 per cent oil respectively, and this inverse relationship between seed size and oil percentage (r = −0·9635) was attributed to the increase in proportion of hull in large seeds. In a pot experiment, plants from large seeds emerged earlier than those from small seeds when sown at both 1 and 3 inches depth. Further, plants from large seeds had greater dry weights and leaf areas than the others. The same sort of correlation was also obtained between seed size and early emergence in a field experiment using small, medium and large seeds.

The effect of no-tillage and mulch on soil properties and tuber yield of cassava was studied over a five year period on an infertile, acid Ultisol in south-eastern Nigeria. Mulch was applied at a rate of 12 t ha−1 as a split application once at planting and once six months after planting. No chemical fertilizers were used during the trial. Bulk density and proportion of micropores (pore radius, r, <1.4 µm) were greater, and proportion of macropores (r>14.4 µm) lower, with no-tillage. Water infiltration was increased by mulching, being greatest in tilled, mulched plots. Soil chemical properties were not significantly affected by tillage system, although levels of exchangeable calcium, magnesium and potassium were higher and acid saturation lower with mulching. Soil physical and chemical properties were best with tillage and mulching, and poorest when neither tillage nor mulch was used. Cassava tuber yield was unaffected by tillage system but increased by mulching.

Several methods of measuring and estimating the available-water capacity of soils with varying degrees of accuracy are described. The errors associated with the use of the different techniques on a wide range of soils have been calculated and suggestions are made regarding the choice of method for particular circumstances.

A field experiment was conducted for two consecutive years commencing in 1979–80 on the Indo-Gangetic alluvial soil of Pura to investigate the requirements for zinc of wheat, chickpea, mustard and Egyptian clover. Chickpea and Egyptian clover were more sensitive to zinc deficiency than wheat and mustard, respectively. Average total dry matter production by Egyptian clover and wheat was larger than mustard and chickpea. Egyptian clover and wheat required more zinc to achieve maximum dry matter production but they also recovered from the soil a larger proportion of applied zinc than chickpea and mustard. Mustard produced the most dry matter per unit of zinc absorbed.