Nepalese hillside terraces are classified into two broad groups, sloping or bari terraces which are only rainfed, and level or khet terraces which are commonly flood irrigated but may also be rainfed. Although such terraces may be adjacent, the process of irrigation by flooding and puddling changes the pattern of variability both within and between terraces. Data collected from Pakhribas Agricultural Centre, Dhankuta, Nepal, were used to describe this variability. The variability is manifest not only in the soil characteristics of the two terrace types, with khet terraces being more uniform than bari terraces both within and between terraces, but also in the variability of field experiments on the two terrace types. However, both terrace types exhibit similar patterns of variability which influence the design of experiments. These include the following: a gradient between the terrace riser and wall which is generally more important than gradients along the terrace, variability within terraces which can preclude the assumption that plots on the same terrace are similar, and variability between terraces which requires experimental units in the same block to be assigned to the same terrace.

A long-term field trial was conducted to determine yield trends in relation to nutrient uptake and efficiency in different rice-based cropping systems. The cropping systems had a significant effect on wet season rice yield when residues were not recycled but had no effect otherwise. Rice yield decreased after the first year of crop residue incorporation but increased every year thereafter. Rice yield was significantly affected by residual nutrients applied to dry season crops. The highest residual effect was observed in tomato and sweet pepper to which the highest nitrogen (N), phosphorus (P) and potassium (K) rates were applied. Maize, sweet pepper, and tomato responded well to NPK application, garlic had a low response and mungbean had no response. A relay crop served as a catch crop for excess nutrients and as shade to minimize sunscald effects for tomato and sweet pepper fruits.

The possibility of producing herbage of higher quality than that of tall fescue (Festuca arundinacea) in a continental climate with cold winters, hot summers and low precipitation was investigated, with and without irrigation, at Taigu, Shanxi, China. Tall fescue was compared with perennial ryegrass (Lolium perenne), meadow fescue (Festuca pratensis) and perennial ryegrass × meadow fescue in field swards, managed by cutting, during the year of sowing and in the three subsequent years. Perennial ryegrass yielded well in the year of sowing, but was low yielding subsequently; perennial ryegrass × meadow fescue yielded well in the year of sowing and in the following year. Both of these grasses had high rates of leaf appearance and extension and a high proportion of cell content in the dry matter. Tall fescue yielded well, but was low in proportion of cell content.

The effects of drought and plant density on fractional interception (f), radiation-use efficiency (RUE) and dry matter accumulation and partitioning to seeds in cowpea (Vigna unguiculata) need to be quantified in order to calibrate cowpea simulation models for West Africa. Accordingly, a short duration cultivar of cowpea, IT84S-2246-4, was grown at a range of plant densities in well-watered and drought conditions in 1990–91 at two contrasting locations in Nigeria, Ibadan (7°N) and Kano (12°N). Fractional interception of radiation (f) and total above-ground dry matter accumulation (TDM) were measured throughout the growing season and TDM and seed yield (SY) were measured at maturity. At Ibadan drought had no effect on phenology while at Kano drought increased the duration of the vegetative phase (by 5–6 days), but not of the reproductive phase. Drought reduced f and radiation-use efficiency (RUE), and hence TDM, and there were significant interactions between RUE and plant density at both Kano and Ibadan. Average SY in the well-watered treatments at Kano and Ibadan were 1600 and 700 kg ha⊃−1&/sup; respectively and drought reduced SY by 50% at both sites but did not interact with plant density. Across locations, plant densities and drought treatments SY was strongly correlated (r = 0.96) with TDM production between flowering and maturity. These data suggest that partitioning of dry matter during the reproductive phase is not affected by location, drought or plant density and the SY of cowpea can be predicted from dry matter accumulation.

Photosynthetic rates (Pn) of China-type high quality tea (Camellia sinensis), clone T78, 44–68 months after field planting, were monitored during the different seasons of 1996 and 1997. The maximum value of Pn (11.9 μmol m−2 s−1) was recorded in October when humidity was very high, temperature, sunshine hours and soil moisture were moderate and photosynthetic photon flux density (PPFD) was highest. Low temperature accompanied by low soil moisture reduced Pn during the winter (February). An important limiting factor for Pn was observed to be moisture stress. An apparent relationship between Pn and relative humidity was observed. In general, higher rates of Pn were recorded during periods of low evaporative demand (low VPD).

Simple models of the growth and development of legume cover crops in different environments may aid the selection of species and genotypes most suitable for particular farming systems. The effects of temperature and photoperiod on the daily rate of seedling emergence (1/t50%) and the rate of leaf appearance (leaves d⊃−1&/sup;) were quantified for 12 diverse legume cover crop species. Six tropical or subtropical species were grown in 12 combinations of mean temperature (16.8, 21.8 and 26.8 °C) and photoperiod (11.5, 12.5, 13.5 and 14.5 h d⊃−1&/sup;). Another six genotypes of temperate species were grown in nine combinations of mean temperature (16.8, 21.8 and 26.8 °C) and photoperiod (12.5, 13.5 and 14.5 h d⊃−1&/sup;). Durations from sowing to 50% seedling emergence (t50%) were recorded and the number of leaves on the main stem counted during early vegetative growth. Photoperiod did not affect either 1/t50% or leaves d⊃−1&/sup;. However, the effects of temperature, photoperiod response group (short-day or long-day response), genotype or species and their interactions were all significant. An optimal temperature between 21.8 and 26.8 °C for leaves d⊃−1&/sup; was identified for Vicia sativa, Vicia dasycarpa and Lupinus mutabilis. Below the optimum temperature, 1/t50% and leaves d⊃−1&/sup; were positive linear functions of temperature for all legume species except Vicia dasycarpa. Estimates of base temperature (Tb) and thermal time (θ) for 1/t50% and leaves d−1 were obtained for each legume cover crop from these functions. Common values of Tb were found within each photoperiod response group: 9 °C and 1 °C for 1/t50%, and 10 °C and −2 °C for leaves d⊃−1&/sup; for short-day and long-day species respectively. Differences among species were represented by variant estimates of θ. The practical consequences of the combined effects of these values of Tb and θ for selecting legume cover crops for particular farming systems are discussed.

Ten planting dates were selected at weekly intervals for the purpose of determining the optimum planting date for two late maturing sorghum (Sorghum bicolor) cultivars in the 1995 and 1996 cropping seasons. Both the floral characteristics and the ultimate grain yield were affected by variation in planting date. The highest grain yield for each cultivar (977 and 958 kg ha−1 for Janare and Farin Dawa respectively in 1995, and 975 and 955 kg ha−1 respectively in 1996) resulted from planting delayed for exactly 51 days after the onset of the rains. Consequently, 10–12 June appeared to be the optimum planting dates for sorghum in the area. A comparison of the result with previous work done in the same ecological unit revealed that delaying planting until 10–12 June increased grain yield by about 25–27 kg ha−1. The effects of the characteristics of the onset of the rains on the optimum planting date have been discussed and the implication of the study for traditional agricultural practice in Nigeria has also been noted.

A long-term field experiment was conducted to determine the effects of indigo (Indigofera tinctoria) on the productivity of rainfed lowland rice-based cropping systems: rice–tomato, rice–tobacco or soyabean, rice–maize, and rice–garlic. Indigo was grown as an intercrop during the dry season and incorporated as green manure for wet season rice. Dry season crop yields were generally not affected by the indigo intercrop but indigo green manure had a positive effect on rice yields. At the same level of nitrogen (N) inputs, indigo-N produced higher yields than urea-N which may be due to high inorganic N losses.

Leaf senescence in the rice (Oryza sativa) cultivars FR13A and IR42 under submergence was assessed in terms of changes in total chlorophyll, soluble amino acids and protein concentrations and peroxidase activity in crude extracts. The objective was to determine whether delay in leaf senescence was related to the submergence tolerance of a rice cultivar. Submergence induced senescence and its extent was notably different in the two cultivars. Results indicated a reduction in chlorophyll and protein concentrations in leaves during submergence but an increase in amino acid concentration and peroxidase activity. These relative changes were more pronounced in submergence intolerant IR42 than in tolerant FR13A even at four days after complete submergence. When plants were desubmerged and returned to standard irrigated conditions after 10 days of complete submergence the rate of recovery was different for the two cultivars. FR13A showed a greater protein and chlorophyll restoring ability compared with the intolerant IR42. The differences observed between the responses of FR13A and IR42 to submergence were likely to be due to differences in proteolysis. Senescence of leaves due to submergence was similar to the senescence of non-submerged excised leaves. Results demonstrate that, in the two cultivars studied, leaf senescence is an important biochemical mechanism in plants under submergence and its slower development in tolerant cultivars is, in part, responsible for submergence tolerance.

Participatory varietal selection in a development project in western India showed that the rice (Oryza sativa) variety Kalinga III was highly preferred by farmers. The spatial diffusion of this variety from three villages (two project and one non-project) was studied. Seed of Kalinga III had spread from the three villages in 1994 to 41 villages by 1996 and is estimated to have reached over 100 widely distributed villages by 1997. Farmer-to-farmer spread was as high from the non-project case study village that received no further seed from the project, possibly because farmers are more likely to spread seed of a new variety to other farmers when they have no assured supply. Project interventions used key villages, informal-sector seed merchants, and Non-Government Organizations in the spread of seed. The project also collaborated with Rajasthan State Agricultural University and Kalinga III has been proposed for release in that state. A financial analysis revealed the very high internal rates of return that are possible from investment in participatory varietal selection.

The adaptation of extra-short-duration (ESD) and short-duration (SD) pigeonpea (Cajanus cajan) genotypes to the short rainy season (late March to late May; yala) was studied in Sri Lanka in 1995 and 1996. Eight ESD and two SD genotypes were sown on two dates in April and May, with and without supplementary irrigation. In addition, pigeonpea ESD genotype ICPL 88039, and SD genotype ICPL 86012, sesame (Sesamum indicum cv. M.I.3), blackgram (Vigna mungo cv. M.I.1) were compared under rainfed zero-tillage conditions after a rice crop at two locations in 1996. Grain yields of the pigeonpea genotypes under rainfed conditions ranged from 0.07 to 0.47 t ha−1 in the early sowings and 0.09 to 0.42 t ha−1 in the late sowings. The irrigated yields reached 1.7 t ha−1 in early sowing and 1.3 t ha−1 in the late sowings. Irrigation differentially influenced the performance of pigeonpea genotypes in both the sowings in 1996. Analysis of pooled data showed highly significant genotype × environment (year–sowing–irrigation combination) interactions. The interaction pattern among genotypes was associated with differences in the length of the reproductive period and the partitioning coefficient of genotypes. ICPL 88039, with the shortest reproductive period and one of the best in partitioning efficiency, recorded maximum mean yield. As a rainfed post-rice crop in farmers’ fields, ICPL 88039 yielded 0.43–1.4 t ha−1 which exceeded yields of SD pigeonpea (0.02–0.88 t ha−1), blackgram (0.03–1.00 t ha−1) and sesame (0–0.09 t ha−1). The results suggest scope for introducing ESD genotypes as a sole crop in the yala season in Sri Lanka since genotypes with short reproductive periods and high partitioning efficiencies are likely to have better adaptation to this season.

Many farmers are intensifying production systems by applying greater amounts of inorganic fertilizers, irrigation and pesticides, especially to cash crops. Such intensified systems, even though economically profitable in the short run, may not be sustainable. This paper analyses the economics and sustainability of an intensified rainfed rice-based system in Ilocos Norte, Philippines. Farmers use high levels of inorganic fertilizers for cash crops such as sweet pepper, garlic and tomato. Although these crops generate high levels of income, the high input systems may not be sustainable in the long run due to adverse on-site and off-site effects. Preliminary estimates of total factor productivity that include on-site effects only, display no clear time trend. However, negative externalities created by high nitrate contamination of groundwater and high rates of pesticide usage could make the system unsustainable by adversely affecting human health and the environment.

Some agronomic, economic and ecological aspects of an agroforestry system combining Grevillea robusta trees, bananas (Musa spp.) and beans (Phaseolus vulgaris) were studied in the subhumid highlands of Burundi. Three densities of G. robusta, 208, 313 and 625  trees  ha−1 were interplanted in plots of bananas, beans and a banana–bean mixture. When G. robusta was interplanted with bananas, the tree had a positive effect on banana yield with maximum yield occurring at 300  trees  ha−1. In the presence of beans, banana yield was not influenced by the densities of the tree. Under low fertility regimes, the yields of beans interplanted with G. robusta were equal to or greater than those of the no-tree plots. Maximum bean yields were observed at between 283 and 295  trees  ha−1, representing a 25–135% yield increase above the no-tree control. When soil fertility was raised by the application of fertilizers, bean yields declined with an increasing density of G. robusta. Three years after planting, the growth of G. robusta was not affected by tree density. Mean height and mean basal diameter were 7.1   m and 13.2   cm respectively. Below ground competition between beans on the one hand, and bananas or bananas and G. robusta on the other, was more important than competition for light. Compared with the crops alone treatments, cumulative net present values of tree plots improved from being negative in the first year to being positive in the third year. Net present value was highest in two of three instances when the density of G. robusta was 625  trees  ha−1. A multistrata arrangement of bananas and beans with G. robusta is viable for the low input agriculture system of the highlands of Burundi.

A series of experiments on communally-owned grasslands in the barley–livestock zone of north Syria were conducted to test the hypothesis that introduction of Mediterranean annual legumes will increase productivity. The experiments were preceded by a survey to determine farmers' attitudes, describe the farming systems and to select appropriate collaborators. The first experiment examined the establishment of medics (Medicago spp.) and clovers (Trifolium spp.) distributed by hand, and monitored their effects on biomass and seedbank size. Later experiments extended these results to other villages. The principles of farmer participation in research were used to overcome the constraints imposed by the communal ownership of land. 

The survey revealed that the average size of the 20 villages was 36 families and that each village owned 887 sheep and 790 ha land. All villages had access to communally-owned grasslands, although their dependence on income from sheep varied greatly. These villages were subsequently divided into groups of high, intermediate and low potential.

Of the 11 clovers sown in the first experiment, seed numbers of T. tomentosum, T. purpureum, T. haussknechtii, T. pilulare and T. resupinatum increased over three years. By 1996, there were more than 3000 legume seeds m−2 in the seeded treatment compared with less than 2000 in the unseeded treatment (mainly the naturally-occurring Trigonella monspeliaca). The number of medic and clover seedlings also increased significantly, while the number of Trigonella seedlings decreased significantly. Biomass production increased in the final two years and there was no response to added phosphorus.

There were similar results in the later experiments. Seedbank size was greater in seeded treatments than in unseeded treatments, there were more seedlings in the seeded treatments, and the most successful species were T. campestre, T. tomentosum, T. speciosum and M. rigidula. The response in biomass was limited to the legume component, although total biomass increased in at least one of the two years. The highest biomass produced was 1112 kg ha−1 and there was no response to added phosphorus.

The results suggested that the on-station research previously conducted at ICARDA headquarters was applicable to communally-owned land, although important modifications were needed. For example, at ICARDA phosphorus was necessary to stimulate the growth of legumes; in contrast, it was necessary to sow legumes at the four villages involved in these experiments. The results also suggested that the grasslands were common property, owned and controlled by defined groups of farmers.

Cutting and carrying of mulch from established tree plots is an alternative to in situ mulch in agroforestry systems. Through the cut-and-carry method, the undesirable effects of tree-crop competition characterized by in situ mulching can be avoided. An economic evaluation of the cut-and-carry method of providing nutrients for maize production was carried out based on investigations in south-western Nigeria. The results showed that the use of mulch from multi-purpose trees (MPTs) through the cut-and-carry method contributed to higher maize grain yields than those obtained with fertilizer or in the untreated controls. However, because of high labour requirements and scarcity of land in the study area, providing nutrients for crop production by this method is unprofitable both in the short and the long term. This may serve as a constraint for the adoption of this technology by farmers. Alternative options requiring less labour and land requirements should be investigated in the quest to replace shifting cultivation.

Under rainfed conditions in Tarlac, Central Luzon, Philippines, risk was characterized using field and household panel data for 46 rice farmers over the period 1990–93. Measures of risk at the field level were calculated using pooled time-series cross-sectional data. Field-level risk was found to be quite high, with the average coefficient of variation of yield being 45% and 30% for fields with low and moderate elevations respectively. Farmers applied less nitrogen in fields with higher yield variability, and adjusted the quantity of nitrogen in order to reduce losses in poor years and benefit from greater potential in good years. Farmers with higher levels of education had lower variability of rice income than farmers with a lower level of education. Non-crop income helped reduce total income variability, especially for farmers with high variability of crop income. Implications for technology design and policy improvements are derived from these results.

Transient soil-moisture-deficit stress was imposed on groundnut (Arachis hypogaea) at three phenophases for different durations: long stress in the early vegetative phase (20 days after sowing); moderate stress in the early vegetative phase (20 days after sowing); stress at flowering (40 days after sowing); and stress at pod development (60 days after sowing). Stress was imposed for 30 or 25 days at the vegetative stage. Transient soil-moisture-deficit stress, at all phenophases, reduced the production of flowers. Soil-moisture-deficit stress for 25 days at the vegetative phase followed by two relief irrigations at an interval of 5 days, resulted in closely synchronized flowering. This factor contributed to a greater efficiency of conversion of flowers to pods and to higher pod yields. Total biomass accumulation was also higher in plants which experienced stress in the vegetative phase. Groundnut pod yields were increased by imposing a transient soil-moisture-deficit stress in the vegetative phase for 25 days, followed by two irrigations at an interval of 5 days. Thus stress in the vegetative phase was beneficial for groundnut growth and pod yields, but was highly detrimental when imposed at flowering and pod development.