The paper outlines ways in which agricultural scientists fail to benefit fully from collaboration with statisticians and mathematicians and from the use of computers. These result mainly from misunderstandings and wrong attitudes; the aim here is to correct them by frank examination. A statistician can easily point comment on how his attempts to cooperate with others are rendered ineffective, and many examples are quoted. He must also recognize and seek to correct his own weaknesses; the paper has no intention of minimizing these, though its chief concern is with other matters. The emphasis throughout is on statisticians and mathematicians being collaborators in research, not merely purveyors of specialized services, on computer use being coherently planned, and on scientific management being concerned with priorities.

Genotype-environment (GE) interactions as a component of historically rising crop yields are reviewed. For various cereals (both temperate and tropical), past selection has seemingly evoked responsive varieties, and GE effects constitute about one third of the total estimated yield increase due to G + E + GE. In potatoes and sugarcanes, more stable (less responsive) varieties, less dependent upon good environments to do well, have been prominent. Historically, responses have been largely due to unconscious selection, but GE effects could be deliberately manipulated by breeding if it were desirable to do so, for example, to produce varieties adapted to low-input agriculture (already an object of breeding research in a few crops).

Our experience with potentially tropic-adapted grain legumes leads us to hypothesize that ‘with appropriate and sufficiently proven technology, developed specifically for the purpose, controlled environment facilities can be a powerful adjunct to field research and so assist in the attainment of crop improvement objectives in lentils’. This contribution comments on the ‘adaptation’ of grain legume crops to their environments, describes current lentil production in the USA and elsewhere, and discusses the tenets and objectives of a programme of research devoted to the ultimate release of lentil genotypes that are well adapted to the environments for which they are intended.

In recent years many economists have been posted to agricultural research stations in Africa but their roles and methodologies have not been clearly defined. Maize research in Nigeria has an exceptionally good structure, good facilities and highly trained manpower, yet the innovations recommended to farmers are not entirely satisfactory. Deficiencies are the result of inadequate attention to the way innovations fit into the farm-household system, identification of farmer's objectives, the uses made of maize and problems of resource shortage. Pilot studies demonstrated how these deficiencies may be rectified by an economist, and suggest changed production recommendations and research priorities.

The effect on maize yields of ground rock phosphate, alone or mixed with sulphur in either of two proportions, and of single-superphosphate, was measured at five consecutive harvests. At the first harvest single-superphosphate increased yield by 1.54 t and the best of the mixtures by 0.56 t grain/ha. Ground rock phosphate alone had no effect on yield. At the third harvest there were no yield differences between sources; because yields produced by rock phosphate and the mixtures improved. The cumulative increase in yield produced by single-superphosphate was 3.58 t/ha and by rock phosphate 2.69 t grain/ha, but because the fertilizer cost ratio was 3:1, additional grain produced by rock phosphate cost half as much. The apparent P recovery ranged from 5.40 to 8.28 kg/ha, with most from single-superphosphate and least from the mixture containing most elemental-S.

In field trials a population of 61,700 maize plants/ha produced higher total dry matter and grain yields than the conventional 36,000 plants/ha. There was no difference in yields with inter-row spacings of 45, 60 or 90 cm, regardless of population levels. Weed suppression was increased by the higher population even though the entire experimental area was treated with herbicides. In one of three years perennial sedge and annual weed growth started 4–5 weeks after herbicide application, under which conditions row spacing had a greater effect and weed growth was significantly less with 45 or 60 cm maize rows than at 90 cm.

Boron treatment was superimposed on half of 48 Amazon cocoa NK-treated plots in four locations across Southern Nigeria. Boron was deficient in soil and leaves of untreated 12-year-old Amazon cocoa, but boron treatment increased bean yield from 13 to 70%. Application of N and K fertilizers reduced the impact of soil-applied boron.

The total growth increment of sugar cane stalks from 13 to 22 weeks after planting was 55% greater in elevated than depressed areas in fields flooded intermittently during the period of measurement. The weekly growth increments were 137–9% greater in elevated than depressed areas, especially when soil moisture was high. The cane was on top of high ridges but water stood up to 10 cm deep over the top of the ridges in depressed areas for up to 5 or 6 days after rain and at varying depths below the top for several more days. Provided the soil was not submerged, tillers elongated most when the soil profile was saturated or nearly so; mere waterlogging without submergence seems not to damage cane. Tiller elongation and soil moisture were well correlated regardless of depth of sampling between 0 and 45 cm, but different relations were obtained for elevated drained areas and depressed areas subject to submergence.

Land Equivalent Ratio (LER) and cowpea growth attributes were used to evaluate three different maize cultivars for intercropping with cowpea, a low canopy crop. The relatively short maize cultivar (Kewesoke) with erect upper leaves transmitted the most light to cowpeas, followed by a liguleless erect-leaf type and then a floppy-leaf type. The more the transmitted light, the greater were the growth and yields of associated cowpeas.

The parasitic weed striga had significantly greater effects on sorghum yield components than non-parasitic weeds. Grain reduction caused by striga amounted to 65% compared with 32% reduction caused by non-parasitic weeds. Comparable reductions were also manifest in straw yield, grains/head and plant height of sorghum. Early removal of striga (a week after its emergence), and thereafter at regular weekly intervals, may help to improve crop yields.

Preliminary evidence is presented in this study for the existence of (1) intraspecific physiological variants of Striga hermonthica, with Gabob population as the most responsive strain to a range of Sorghum bicolor cultivars, and (2) a local Sudanese sorghum cultivar called Tetron with broad-spectrum resistance to striga. Thus Tetron may be recommended as another standard resistant cultivar with reference to Framida of East Africa.

Nitrogen-atrazine combinations were significantly more effective in stimulating higher yield components of sorghum and depressing yield components of striga than sole treatments of either nitrogen or atrazine. Over all treatments nitrophoska at 129 kg N/ha in combination with atrazine at 1.75 kg/ha gave 224, 180, 155 and 151% increases in yield components over the control for head, straw, 1000 grain weights and plant height of sorghum, and a decrease in 83, 88 and 90% of striga density at 8, 12, and 16 weeks from sowing the sorghum. The synergistic effect of nitrogen-atrazine is demonstrated.

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.