Field irrigation is costly in arid regions, and over-fertilization of farmland can lead to high groundwater nitrate levels and significant environmental challenges. Integrative aquaculture and agriculture (IAA) systems allow the reuse of water and nutrients to offset production costs while promoting greater sustainability. The aim of this study was to test the effectiveness of an IAA system using treatments formed from one water source, groundwater (GRND) or fish pond effluent (EFF), and one chemical fertilizer regime, eliminated (ELIM) or historical (HIST). Treatments were applied to field plots of barley or cotton. There were typically positive effects of EFF applications on crop growth and yield relative to GRND applications under identical fertilizer regimes. However, GRND-HIST almost always outperformed EFF-ELIM, suggesting that substituting effluent irrigations for a historical fertilization regime without pond biosolid or reduced fertilizer applications could be detrimental to crop production.

A field experiment was conducted to study the effect of leaf stripping, de-tasselling and topping on the yield of maize and finger millet in a maize/finger millet intercropping system at Lumle in Nepal. De-tasselling of maize before pollen shedding reduced the number of barren plants, and increased test weight and grain yield but de-tasselling after pollination had no significant effect. Defoliation of maize by removal of leaves below and above the ear, or by topping 30 days after 50% silking, had no effect on either maize grain yield or on that of the relay planted finger millet. This contradicts the hypothesis that increased light penetration due to reduced shading improves the yield of millet under maize.

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.

Shoot population densities, stages of development (that is, the number of leaves per shoot) and shoot mass were recorded on an irrigation × fertilizer experiment at the Ngwazi Tea Research Unit in Southern Tanzania from 1986 to 1990. Over this period the mean basal shoot population density increased from about 310 to 560 m−2, with peaks of over 850 m−2 in high-input plots. Large fertilizer application rates increased both the total number of shoots per unit area and the proportion that were actively growing. By contrast, the main effect of water stress was to delay the peak shoot population density from the warm-dry season until the early rains without affecting the annual mean. Overall, between 20 and 60% of the harvested shoots were dormant, depending on season and fertilizer application rate. Of the active shoots harvested, about two thirds had two leaves and a terminal bud whilst the remainder were split almost equally between shoots with one or three leaves. The fresh mass of individual shoots was linearly related to the number of leaves, with the slope of the line (0.16–0.35 g leaf−1) largely dependent on the season and irrigation treatment. The dry matter content of shoots varied in the range 19–30%, and was primarily determined by the season. The dry matter content was also affected by the treatments and was decreased by irrigation in the dry season and by fertilizer in the wet season. Alternative models for predicting annual yields (based on the components of yield) and seasonal yield variations (based on dry matter production and partitioning) are discussed.

Densidad de poblacióon tamaño y masa de los brotes de té

Upland rice and Stylosanthes guyanensis were sown simultaneously in pure and mixed culture at varying densities at Na Pheng, central Laos. Vegetative growth of the rice was negatively related to stylo density over the range o to 81 stylo plants/m.2 Rice grain yield varied from 98·4 gm./m.2 in monoculture to 63·4 gm./m.2 when grown with 81 stylo plants/m.2 Rice was more competitive than stylo, but stylo growth was relatively independent of rice density over the range 20 to 120 rice plants/m.2

A long-term field study was conducted from 1979 to 1985 in the Karnal district of Haryana, India to evaluate the effect of three rates of gypsum (0, 5.2 and 10.4 kg ha−1) on the performance of five grasses (Diplachne fusca, Panicum laevifolium, P. antidotale, Chloris gayana and Cynodon maritimus) on an extremely sodic soil with an initial pH of 10.6 and an exchangeable sodium percentage (ESP) of 94. Diplachne, Chloris and Cynodon usually gave their maximum yield in the second year of planting, P. antidotale in the third year and P. laevifolium in the fourth year. The results showed that Chloris can be recommended for such situations as it maintains a higher productivity over a longer period than the other grasses. Alternatively P. antidotale and P. laevifolium can be planted in association with Diplachne to provide a steady forage supply for a long time. Increasing doses of gypsum resulted in decreases in soil pH, exchangeable sodium and ESP and increases in calcium, magnesium, organic carbon and the infiltration rate of soil.

Sorghum hybrids and varieties show similar responses to changing environment, with constant relative yield increases from the hybrids over a wide range of conditions due almost entirely to more florets and grains per plant and per hectare. Carbohydrate production of the leaves of good varieties is probably not much in excess of requirements for filling the grain. The extra spikelet number of the hybrid, increases in photosynthetic area and probably increased photosynthetic efficiency together enable the extra grains be filled. There is also an advantage in size and activity of the root system. The yield increase is strongly buffered against environmental fluctuations. The fact that hybrids can increase over a wide range of farming conditions should result in big increases in production simply by changing from varieties to hybrids, as is already happening in several countries.

The objective of this study was to evaluate morphogenetic and structural characteristics of Guinea grass pastures subjected to two grazing frequencies (90 and 95% light interception) and two post-grazing heights (30 and 50 cm), during the rainy season and dry year. The leaf appearance rate varied only in the summer, the grazing pastures managed at 90/50 (light interception/post-grazing height) presented higher values in the leaf appearance rate (0.440 leaf/tiller.day), compared with those managed at 90/30 (0.275 leaf/tiller.day) and 95/50 (0.228 leaf/tiller.day), respectively. In the winter/beginning of the spring, pastures managed at 90/30 (0.03 cm/tiller.day) presented lower stem elongation rate in comparison with those managed at 90/50 (0.19 cm/tiller.day) and 95/30 (0.16 cm/tiller.day). Management strategies do not compromise the tissue flow in tillers and, consequently, can be utilized for the management of Guinea grass.

The future evolutionary potential of pulses is determined by the nature and extent of the genetic variability in the primary gene pool. This is extensive in the major grain legumes, notably the groundnut, soyabean, Phaseolus and faba beans, and in the cowpea. It is less extensive in the cultivated lupins and this appears to be a serious limitation to their development as useful crops. The considerable development of isolating mechanisms between related species of legumes has restricted the development of the secondary gene pool. This is most developed in the genus Arachis, where section Arachis provides an extensive secondary gene pool for the groundnut. Tertiary gene pools are potentially quite extensive for many grain legumes but since most interspecific hybrids are inviable this resource would be difficult to exploit with present techniques. The development of sophisticated gene transfer techniques for grain legumes is inhibited by their lack of amenability to in vitro culture. The suggestion is made that genetic resources profiles could be constructed on the basis of an expansion of Harlan and de Wet's gene pool system. These could serve as a guide to the present state of germplasm collections, indicating their strengths and weaknesses, which would be useful in formulating future collection and evaluation strategies.

The potential for more intensive exploitation of such legumes as the winged bean and lupins undoubtedly exists. The reasons for past under-exploitation of the winged bean need to be determined.

Grain legumes have an assured future for good economic and nutritional reasons. More attention probably should be devoted to exploiting the legume-Rhizobium symbiosis, fundamental to the development of efficient and economic farming systems in the developing world.

Growth of the sunflower cultivar Peredovic was examined when exposed to periodic severe moisture stress, with and without soil drench application of CCG at the two-leaf stage. The experiment was conducted in sand culture under partly controlled environment conditions. Morphological and physiological measurements were made throughout the growing period. Amongst the responses to CCC were increased stem and petiole width, and decreased length of internodes, head diameter and photosynthetic area. Moisture stress reduced photosynthetic area and the root/shoot ratio. Both CCC and moisture stress increased the number of stomata per unit area.

A large body of evidence demonstrates the agronomic superiority of maize hybrids over open-pollinated varieties (OPVs) in intensive monoculture. However, comparisons of the performance of hybrids and OPVs in agroforestry systems are scarce. In this study, the performance of four maize hybrids and four OPVs is compared in sole crop and under mature trees. Experiments were conducted on-farm during four seasons in Bugesera, Rwanda and two seasons in Meki, Ethiopia. Two tree species were selected in Bugesera (Grevillea robusta and Senna spectabilis) and one in Meki (Acacia tortilis), and three farms were selected for each tree species, each including two plots with almost identical trees in their centre and two plots without tree. In Bugusera, grain yield was higher for hybrids (2 Mg ha−1) than for OPVs (1.5 Mg ha−1), and the presence of trees reduced the harvest index more in OPVs than in hybrids. In this region, the estimated reduction in grain yield due to the presence of trees was 0.9 and 1.1 Mg ha−1 in hybrids and OPVs, respectively, while estimated reduction in biomass was 1.5 and 1.7 Mg ha−1, respectively. In Meki, the grain yield of OPVs (2.08 Mg ha−1) and hybrids (2.04 Mg ha−1) did not differ and the presence of trees reduced their grain yields in the same manner. Our results showed that hybrids yielded more than OPVs under G. robusta and S. spectabilis in Bugesera but performed equally well under A. tortilis in Meki. We conclude that agroforestry farmers could benefit from growing hybrids in the equatorial savannahs of Rwanda, but that the choice between hybrid and OPV in equatorial savannahs of Ethiopia can simply be based on other factors such as seed costs and availability.

At its International Centres Week in October 2000 (ICW2000), the Consultative Group on International Agricultural Research (CGIAR) adopted a new Vision and Strategy. This paper is about Plank 4 of the CGIAR's Vision and Strategy which calls for the adoption, in collaboration with national and regional partners, of a regional approach to research planning, priority setting and implementation. Given the poverty and impact focus of international public goods research, both national agricultural research systems (NARS) and the CGIAR have advantages in pursuing a regional approach as a component of their respective activities. For the NARS in the region, this means seeking advantages at the regional level that they could not derive solely from a national-level approach. For the CGIAR, this means seeking complementary gains that it could not achieve exclusively through a global or ecoregional approach. These mutual advantages open the door for partnerships in regional research between NARS and their regional organizations, and the CGIAR. The paper highlights the advantages as well as risks and limitations of a regional approach to research. Since ICW2000, all regional and sub-regional organizations and CGIAR Centres have taken action to facilitate consultation processes that could eventually lead to the establishment of a regional approach to research for the CGIAR and NARS. The paper notes some emerging lessons, and takes a forward look.

Beans and bananas were grown in sole crop and intercrop systems for three seasons in 1989 and 1990 to determine the effects of cropping system on diseases, insects and land-use efficiency and the roles of certain bean plant physiological traits on bean yield in the two systems.

Bean yield in the intercrop system was 52% of bean sole crop yield. Shading reduced yield, but stem starch levels, chlorophyll content and the chlorophyll a:b ratio were not related to seed yield in either system. Leaf area index was linearly related to yield in the intercrop system, suggesting that a higher plant density may result in higher yields. Nutrient concentration levels in the foliar tissues indicated that low potassium and high manganese availability constrained intercrop bean yield. Leaf manganese levels were higher in beans grown under bananas, reaching levels normally considered toxic for beans. Competition for other nutrients did not appear to affect bean yield. Apparently, interspecies competition for soil moisture did not much reduce bean yields as moisture levels did not differ with cropping system. Disease and insect pest levels were similar for the two bean production systems.

Banana yields were associated with potassium levels in the soil. Bananas appeared to be more competitive than beans in the intercrop system. The land equivalent ratio of the banana and bean intercropping system over the three seasons was 1.60.

A number of studies across sub-Saharan Africa have recently reported poor crop responses and low agronomic use efficiencies of applied nitrogen (AEN), phosphorus (AEP) and potassium (AEK). However, the conditions under which non-responsiveness occurs, its underlying causes and its probability of occurrence on different soil types are not well understood. Using data from 542 sites and 14 soil types in 23 African countries, we provide novel insights into the linkage between lack of response to applied N, P and K, the mineralogy of soils and their resilience to erosion. We estimated mean responses as well as the probabilities (ϕ) of no response in terms of response ratio (RR), yield gain (YG) and agronomic efficiency. Here we defined ‘no response’ as zero agronomic response to fertilizer inputs in a given site and year indexed by either RR ≤ 1, AEN ≤ 0, AEP ≤ 0 or AEK ≤ 0. The highest risks of no response were recorded on the iron-rich Plinthosols (ϕ = 0.26) followed by the aluminium-rich Alisols (ϕ = 0.16) and the erosion-prone Lixisols (ϕ = 0.16) and Leptosols (ϕ = 0.13). In terms of yield gains, the highest risk of low response (i.e., YG ≤ 0.5) was recorded on Alisols (ϕ = 0.47) and the lowest on Fluvisols (ϕ = 0.05). Cambisols, Fluvisols, Luvisols and Nitisols were deemed highly responsive to NPK fertilizer. The risks of no response were significantly higher on soils derived from siliceous than mafic parent materials, soil types with low resilience to erosion, soils with low-activity clays and high P fixation capacity. It is concluded that maize grain yields can exceed 3 t ha-1 with high probability (ϕ > 0.80) on Andosols, Nitisols and Vertisols, but with very low probability (ϕ < 0.30) on Alisols and Arenosols. It is also concluded that across soil types and agroecological zones, the risk of no response is up to two times more on farmers’ fields than on research stations. Here, we discuss the implications of these finding for the design and location of future agronomic trials. We also provide insights to guide the targeting of fertilizer subsidies where nutrients can be more efficiently used.

In agricultural innovation, the success of widely used technologies is often assumed to have been inevitable. Conversely, the blame for the failure of new technologies that researchers, policy makers and extensionists consider superior to existing solutions is often placed on farmers. However, these assumptions can be challenged by taking a social-constructivist view of on-farm innovation to examine how and why farmers made sense of new technologies and how this sensemaking shaped their use of these technologies over time. The present study took such an approach in its analysis of Australian woolgrowers’ adoption, abandonment, implementation and use of new wool-testing technologies that highlighted the social and dynamic nature of innovation on-farm. On-farm innovation in this case was an evolving, dynamic process that changed over time as woolgrowers made sense of new technologies. The primary message to agricultural innovation researchers, technology developers, policy makers and extensionists is that successful on-farm innovation requires the active, ongoing engagement of industry participants. In order to engage industry participants in the innovation process, sensemakers’ personal identity frames and social context, and how these interpretation frameworks relate to the new technology need to be understood.

The systematic rather than random entry arrangement of honeycomb designs (HDs) has been deployed to sample the spatial heterogeneity. This hypothesis was studied in fairly homogeneous populations, assuming that their phenotypic variability stemmed absolutely from spatial rather than genetic heterogeneity. It was based on single plant performance in two separate trials of a maize hybrid and a wheat cultivar reflecting different level of spatial heterogeneity. In general, the HDs counteracted spatial heterogeneity well, particularly when the number of evaluated entries was limited. There was a suggestion that they do well even in a high number of entries with many replicates per entry. Distribution and layout of spatial heterogeneity across the experimental area did not affect the precision of the HDs. Standardized configuration, which ensures implementation of essential principles met in other experimental models such as blocking, replication and nearest-neighbour (NN) adjustment on the same baseline, renders the honeycomb experimental pattern advantageous over the classical experimental designs like the randomized complete block (RCB), the NN method and the lattice model.

Four surface sterilization agents and two hot-water treatments were evaluated with a view to eliminating bacterial contamination in sugarcane (Saccharum hybrids) buds used for in vitro initiation. None of the treatments achieved total elimination of contaminants. Disinfection in either a 2.7% solution of sodium hypochlorite (pH 6) or 1% mercuric chloride were equally good, resulting in 46.8% and 56.3% clean cultures respectively. However, sterilization with 2.7% sodium hypochlorite (pH 6) was most phytotoxic and 100% tissue necrosis and bud death were recorded. The Australian cold-soak hot-water treatment (consisting of a 48-h soak in running water followed by hot-water treatment at 50 °C for 3 h on the following day) reduced contamination from 70% to 25%. With the dual hot-water treatment (setts immersed in water at 52 °C for 20 min and then at 50 °C for 3 h on the following day) a decrease to 45% was observed. Bacterial contaminants were identified by fatty acid profiling and were found to belong mainly either to the Enterobacteriaceae family or the genus Bacillus.

Six products possessing suitable physical properties as fluid carriers for pre-germinated seed were assessed for their effects on seedling emergence. Both glasshouse and field experiments measured the carriers' performance on eight crop species at varying extrusion rates and under different environmental conditions. Synthetic clay or polyacrylate increased seedling emergence by 10% compared with the sodium alginate control. Seedling emergence was least affected by moisture stress when synthetic clay was used as the carrier.

In a genotype × environment experiment at four sites with four tea (Camellia sinensis) clones in Kericho, Kenya, differences in ground cover and total dry matter production and partitioning were found between clones and between sites. The major contributor to these differences was the daily intercepted solar radiation that differed by as much as 30% between sites. Differences in radiation use efficiency (RUE) between the sites were small, but varied from 0.3 to 0.45 g MJ−1 between the clones. The rate of dry matter production was affected by the prevailing weather conditions. During the dry seasons the rate of dry matter production differed between the sites and clones by a maximum of 2 g m−2 d−1. Harvest indices were found to vary between the sites and increased with time. Partitioning to harvested shoots ranged from 10% for clone TN14-3 to a maximum of 19% in clone S15/10 at site 4. Partitioning to roots showed distinct differences between clones, being least in clone S15/10 (10–20%) compared with 15–32% in other clones. Rooting depths were greatly influenced by the prevailing temperatures.

A technique is described that allows neutron meter access tubes to be reinstated in tilled soil without disturbance below the depth of ploughing or tine cultivation. In a test there was no evidence of greater water movement to depth around reinstated access tubes compared with newly inserted ones.