Farming Systems Research (FSR) has emerged as a major theme in international agricultural research in the past decade. However, despite widespread use of the term, its meaning and the types of research objectives, approaches, activities and methods to which it applies remain ambiguous. The lack of precision in concepts and terms will discredit FSR and jeopardize donor support. This paper seeks to clarify and define the major types of research approaches and activities encompassed by the general term FSR. Six types of research are distinguished and a new, more precise terminology is proposed.

The study was carried out in an unheated glasshouse under natural conditions of daylength and temperature. Rates of pod and seed growth and development, and of desiccation at maturity, are reported in single genotypes of Lupinus albus, Lupinus mutabilis, Vicia faba, Pisum sativum and Lathyrus latifolius. The histology of tissue layers in pods are also described. The culti-var of Pisum sativum completed dry weight accumulation in pods in 20 days from anthesis; the equivalent time in Lupinus albus (Kievskij mutant) was 60–70 days and in genotypes of Lupinus mutabilis and Vicia faba about 50 days. The heavier pods and seeds of the L. albus and V. faba cultivars were due to a prolonged rapid growth phase: rates of weight accumulation in seeds during the rapid growth phase were similar for all cultivars. The histology of the pod wall varied between species but the rate of dehydration of pods was not a factor in determining date of maturity. The results are discussed in the light of reservations based on known intra-specific variation in crop species.

A simple yet effective field screening technique for estimating drought tolerance is described. It involves growing plants in sloping plots which are opposite each other and connected to sub-channels lined with polyethylene sheet. The slopes are designed to achieve instant surface run-off and the sub-channels connected to a main channel for rapid drainage of rain-water. Stress is created at different stages of crop growth by manipulating the timing of irrigation and covering the soil surface with polyethylene sheeting. The technique proved effective even in the monsoon season which is characterized by irregular intensity and distribution of rainfall. Data on six characters for 80 genotypes of pearl millet grown in six artificially created environments representing different levels of moisture stress are discussed. The ‘slope’ technique was effective in creating different levels of moisture stress at various stages of crop growth and in distinguishing categories of genotypes by their relative drought tolerance.

The effect of strain of Rhizobium and of temperature on nodule formation and early growth of Trifolium semipilosum was studied in controlled environment cabinets. Time required for nodules to form was affected by strain of Rhizobium and by root temperature, acting independently. Strains CB788 and CB2116 required only 9.5 to 10.0 days, averaging over temperatures, whereas strains CB782 and CB526 required 12.8 to 13.0 days. Nodulation was earliest at whole-plant temperatures of 25/20°C and 30/25°C day/night (average 9.5 days); 15 days were required at 20/15°C. Nodule number was independent of bacterial strain but dependent on temperature; nodules were fewest in the lowest and most in the highest temperature regime. Plant yield was determined by interactions between temperature and strain and was generally greatest at whole plant temperatures of 25/20°C.

When nodulated plants growing at 25°C were transferred to a range of root temperatures, plants grew best at 20° and 25°C and with strains CB782 and CB2116.

Changes in plant dry weight and nitrogen content of Trifolium semipilosum cv. Safari and T. repens cv. Grasslands Huia were monitored when the root systems of effectively nodulated 28-day-old plants were exposed to a range of constant and diurnal temperatures for 21 days. Nitrogen fixation was more sensitive to high root temperatures than was dry weight accumulation, and T. semipilosum was relatively more tolerant of high root temperatures than T. repens for both dry weight and nitrogen content. The optimum temperatures for dry weight yield and nitrogen fixation (≡nitrogen content) were similar (21–23°C) for both species.

Our data suggest that growth and nitrogen fixation in T. semipilosum are more tolerant of short-term exposure to increase in root temperature than in T. repens. In addition, both species accumulated more dry matter and fixed more nitrogen when night temperatures were reduced from either 30 or 35°C to 25°C. The increase was greater with T. semipilosum and may be a major factor in its adaptation to the humid subtropics and cooler (elevated) tropics.

Two field experiments were conducted to evaluate the efficiency of rate, mode and time of application of manganese sulphate to irrigated wheat on manganese-deficient loamy sand (Ustipsamments) soils recently brought under rice. A significant increase in manganese uptake by wheat and marked increases in wheat grain and straw yields occurred following both soil (5, 10 and 20 kg Mn ha-1) and foliar (0.5, 1.0 and 2.0% MnSO4 solution) application of manganese, but foliar application was more effective. A series of sprays initiated before the wheat was first irrigated (26 days after sowing) gave significantly better results than application begun after the first irrigation (32 days after sowing); four sprays of 0.5% MnSO4 solution produced the largest grain yield, followed by three of a 1% solution.

A series of population density and row spacing trials were carried out with sorghum in conditions of increasingly severe water stress from 1980 to 1984. In conditions of reasonable water availability, increasing density resulted in increased leaf area indices, dry weight production and grain yields. In conditions of severely limiting water availability, increasing density resulted in developmental delays, density-dependent mortality and reduced plant dry weights, with little increase in dry weight production per hectare. In these conditions grain yields were reduced by increasing density. The proportion of dry weight allocated to grain declined with increasing density and decreasing plant size, a consequence of the requirement for a minimum plant size to support grain production. When plant size was reduced below a critical range, disproportionately large reductions in grain yield resulted.

Optimum densities for grain production varied from below 10 000 plants ha−1 in dry conditions to over 120 000 plants ha−1 in moist conditions. Medium density treatments produced the largest grain yields on a long term basis, but the low density treatment showed a reduced risk of crop failure and greater yield stability.

Plant growth, development and yield were monitored in sorghum/cowpea intercropping trials in Botswana during the drought seasons of 1982/3 and 1983/4. The cowpea proved to be more competitive than sorghum in these arid conditions, resulting in substantial increases in sorghum mortality and developmental delay, and substantial decreases in sorghum leaf area indices, dry weight production and grain yield. Intercropping in standard rows at medium plant densities resulted in Land Equivalent Ratios considerably less than 1.0, in contrast to earlier trials in Botswana in higher rainfall years which demonstrated intercropping advantages. Low density, wide row intercropping resulted in some small intercropping advantages, suggesting that this treatment may have potential in Botswana's variable climatic conditions.

Two experiments were conducted over a two year period at the International Rice Research Institute (IRRI) in the Philippines to evaluate the effect of a soyabean green manure intercrop on the grain yield of maize. Three rows of soyabeans were interplanted at 50 cm spacing between maize rows 1.5 m apart. Forty two days after planting the two outside soyabean rows were ploughed into the maize rows in a traditional ‘hilling up’ operation. At the zero and lower nitrogen rates, the soyabean green manure resulted in significantly larger maize yields than when maize was grown without green manure, providing the equivalent of 28 kg N ha−1 on the zero nitrogen plots. A response to green manure was also seen at 25 and 50 kg N ha−1. Allowing the central soyabean row to grow to maturity provided additional yield and protein.

This review paper deals with some of the general statistical principles of crop rotation experiments. The basic terminology of the subject is defined. Attention is paid to the fundamental design principle that each phase of a rotation should each year be present in an experiment involving that rotation. The inclusion of ‘auxiliary’ treatments - usually fertilizer treatments - is discussed. Consideration is given to matters influencing the choice of size and shape of plots. The statistician's role in planning a rotation experiment is portrayed as onerous. Emphasis is put on the importance of care and good practice in the management of a long-term agricultural experiment. Complications arising in the statistical analysis of data from a rotation trial are sketched.