Two seed-resistant land races were crossed to a seed-susceptible cultivar to produce Fl, F2, BC1; and BC2 generations. It was observed that seed resistance was conditioned by two unlinked recessive genes and cytoplasmic factors. Similarly, generations derived from a pod-resistant, seed-susceptible cultivar with a seed-resistant, pod-susceptible land race demonstrated that seed and pod resistance are independently inherited.

Although the first or second clonal cuttings of heat-treated sugar cane were widely used for seed, differences were not detected among crop years or locations in the incidence of ratoon stunting disease. Sugar-cane mosaic virus (SCMV) disease was widespread in all areas surveyed; however, the plant cane crop had a lower incidence of SCMV than the first or the second ratoon crop. The estimated cane yield was increased approximately 19·4 t/ha by heat treatment during the 2-year survey period.

The management system used to control the sugar-cane borer (SCB), Diatraea saccharalis (F.), was effective regardless of the crop year or area surveyed. Season-long SCB control was achieved by the use of two (1981) or three (1982) properly timed applications of insecticide and the use of a SCB moderately resistant variety resulting in an average of 6–9% bored sugar-cane internodes.

Poor weed management, particularly with johnsongrass (Sorghum halepense(L.) Pers.), accounted for much of the reduction in cane yield (P < 0·01); the estimated yields of the second ratoon crop were substantially altered, particularly those of farms surveyed in the Bayou Lafourche area.

Blossom-end rot, a non-parasitic disease, was found to occur widely on some oblong varieties of watermelon, causing much damage in the southern region of Oman (Dhofar). Fruit contact with soil surface seems to be the major agent of blossom-end rot of watermelon, especially in the early stage. Incidence of watermelon blossom-end rot was apparently reduced by mulch using a mixture of dried grasses or coconut leaves.

A new tillage procedure was examined for the improvement in physical environment it might provide during the establishment of a vegetable crop, particularly in a dry spring. This procedure, of cultivating the soil mainly in autumn, was compared with the conventional method of cultivating in the spring on a sandy loam soil. The physical condition of seed beds prepared by the two methods was assessed by in situ measurements of soil temperature, water retention characteristics, hydraulic conductivity and surface roughness. Plant responses were compared by monitoring the emergence of onion seeds. Dry spring conditions were simulated by sheltering some plots from rain.

Final emergence, emergence time and rate of emergence were all superior following autumn cultivation for both dry and wet seed beds. The major factor affecting emergence was the coarseness of the seed bed which influenced the mechanical impedance to shoot growth. Differences in soil temperature between treatments were small, as were hydraulic conductivities under dry conditions. Preparing a seed bed in autumn rather than spring resulted in a good tilth with lower mechanical strength. This minimized the constraints on emergence when soil strength increased under dry conditions.

The conventional Kjeldahl method which is usually employed for determination of total N in soil does not effect quantitative recovery of NO2- or NO3- (Bremner, 1965). Therefore, various modifications have been suggested (Cope, 1916; Davisson & Parson, 1919). Bremner (1965) observed that the quantitative recovery of NO2- and NO3- by any method, other than the modified Olsen's method (Bremner & Shaw, 1958), is not certain.

In tropical and subtropical areas many cattle suffer from heat stress for more than half of each year. Added to the environmental heat stress is the heat production associated with lactation (Berman et al. 1985) and the resultant increased storage of heat (Araki et al. 1984). While the net effect of lactation on body temperature has been evaluated in dairy cattle (Collier et al. 1982) its effect on beef breeds in tropical and subtropical areas has not been defined. This is now possible with improved telemetry equipment, which allows body temperatures of free-ranging cattle to be monitored up to distance of 400 m.

Predatory arthropods can play an important role in the natural control of cotton pests, including bollworms (Heliothis zea Boddie and H. virescens F.). Smith & Fontenot (1942) reported that widespread use of calcium arsenate in cotton fields reduced the number of coccinellids, which resulted in increased damage by pests. Ewing & Ivy (1943) confined several predacious insects collected from cotton (individually in jelly glasses fitted with slightly moistened blotting paper) and supplied them daily with eggs deposited by insectary-reared bollworm moths. The maximum number of eggs destroyed in a day by a single adult of the convergent lady beetle (Hippodama convergent Guerin-Meneville) was 275. Adults of another species of lady beetle (Coleomegilla fuscilabris Muls.) frequently consumed all the eggs given them, an adult on average consuming 22 eggs per day. All the 12 species of predacious insects found in cotton fields survived on bollworm eggs. Whitcomb & Bell (1964) showed that the three most common lady beetles in cotton fields in Arkansas were: (1) spotted lady beetles (Coleomegilla maculata De Geer), (2) convergent lady beetles, and (3) ninespotted lady beetles (Ciccinella novemnotata Herbst). They recorded 24 species of lady beetles, all feeding on lepidopterous eggs including those of bollworms. Many of these predators were captured while feeding on small bollworm larvae. Van den Bosch & Kagen (1966) proposed guidelines for the mass releases of convergent lady beetle adults as a pest control measure in cotton. Lingren, Ridgway & Jones (1968) reported from small-container experiments that adult females of convergent lady beetles consumed an average of 129·9 bollworm eggs per day.

Japanese mint (Mentha arvensis L.), one of the important essential-oil-bearing crops of India, is a potential source of natural menthol which is widely used in various pharmaceutical and cosmetic preparations. Generally under intensive cultivation, the application (broadcast with incorporation) of phosphorus leads to enhanced herb and oil yields of different mint species (Rao, Rao & Singh, 1983; Singh et al. 1983; Vadivel & Sampath, 1981), but the knowledge that P-adsorption to soil surface reduces plant availability suggests that a P application method limiting soil-P contact may improve P availability and use efficiency (Phillips & Webb, 1971). Therefore, the placement depth and method may be an important factor in the proper use of applied phosphorus. Since uptake of P is reduced in dry soils (Reichman & Grunes, 1966; Simpson, 1960), P placed deeper in the soil would remain more available because of increased soil moisture. Another factor involved is the positional availability of the P source (Cooke, 1954). If placed too close to the surface, the roots may not come in contact with the fertilizer or too few would contact the band to maximize uptake.