The Système International d'Unités (SI) provides a consistent and coherent set of units for specifying the magnitude of physical quantities. Use of SI is recommended by most scientific journals and in many, including Experimental Agriculture, it is now mandatory. Multiples and sub-multiples of units should be chosen to minimize the repetition of zeros before or after the decimal point. Several units related to SI (e.g. tonne and hectare) are convenient in speech as well as in writing but should be avoided in analysis to minimize the risk of numerical errors. Units common in agricultural science are discussed with special reference to the need for compromise between consistency and convenience.

A technique to better ensure reliable nodulation of pot-grown, P. vulgaris plants with cultured strains of Rhizobium is described. Nodulation, dinitrogen fixation (acetylene reduction) activity and growth of 28-day-old plants were all stimulated markedly when seeds had been inoculated with cultured Rhizobium phaseoli suspended in alginate gel (Agrigel) rather than in sucrose solution. Nodulation attributes of plants inoculated with R. phaseoli strain RCR 3644 which had been sub-cultured repeatedly on yeast mannitol agar slopes were consistently inferior to those recorded for the same strain but recently cultured from a freeze-dried sample. Some of the potential problems with open pot culture of nodule-dependent legumes are discussed.

Weekly measurements were made of the seed oil concentration (% dry weight) in five sesame genotypes (Sesamum indicum) from flowering to maturity. During early but not late development the oil concentration of main shoot capsules was less variable than that in capsules taken from branches. The oil concentration of seeds from capsules at different nodes decreased from 67 to 22% between the lowest (oldest) capsule at node 8 and the youngest one at the uppermost node (25) in 1976, and from 65 to 19% for the same nodes in 1977. Variations in oil accumulation in relation to capsule age revealed that oil formation begins within 5 days after fertilization and maximum accumulation (52% oil) was achieved after 30 days. The implications of these findings for the assessment of oil yield potential are discussed.

At Hyderabad, India, stands of pearl millet were grown after the monsoon (a) with no irrigation after establishment and (b) with irrigation as needed to avoid stress. Increases of dry matter and leaf area were determined by regular harvesting. The interception of radiation by the foliage, uptake of water from the soil and stomatal conductance were monitored. Before anthesis at 42 days after sowing (DAS), the rate of dry matter production and the transpiration rate in the unirrigated stand were about 80% of the corresponding rates for the irrigated control, mainly because of a smaller stomatal conductance from 30 DAS. After anthesis, the unirrigated stand grew little and used only 10% of the water transpired by the control. This large difference was partitioned between loss of leaf area and smaller stomatal conductance in the ratio of approximately 2:1. Radiation intercepted by foliage in the irrigated stand produced 2.0 g of dry matter per MJ compared with 2.5 g MJ−1 for the same variety growing in the monsoon, a difference consistent with a smaller stomatal conductance in drier air.

The results of field experiments conducted in the spring seasons (February/March to June) of 1980 and 1981 indicate that grain yields of sorghum increased with increase in frequency of irrigation. Crops sprayed with atrazine or CCC yielded more than the unsprayed control; maximum yields were obtained by the application of atrazine at 200 g ha−1. Water use efficiency decreased with increase in irrigation but increased as a result of spraying crops with either chemical. Irrigation water can be saved by the spraying of atrazine or CCC onto spring-sown sorghum.

The effects of irrigation and spraying of transpiration suppressants on growth and nutrient uptake by spring sorghum (CSH 6) have been investigated. Crop growth, measured by plant-height, leaf area index and dry matter production, and uptake of N, P and K increased with more frequent irrigation and in response to the spraying of transpiration suppressants. Foliar applications of atrazine at 200 g ha−1 and CCC at 300 ml ha−1 proved to be the best in this NW Indian location.

The Land Equivalent Ratio (LER) has been generally accepted as an agronomically sound index for assessing yield advantages derived from an intercropping practice. However, LER takes no account of the fact that, in subsistance agriculture, it is usually important to maintain a certain minimum percentage of the pure stand yield of the staple crop component in an intercropping system. A new measure ‘Staple Land Equivalent Ratio’ (SLER) is proposed in this paper which takes account of this requirement. Yield data from intercropping experiments are used to show how SLER can be effective in comparing the yield advantages of intercrop treatments in agronomic experiments.