Yields in a trial of Upper Amazon clones, derived from high yielding Upper Amazon selections, were low in the early years. One Upper Amazon clone was significantly higher yielding than any other clone, but generally yields from the Upper Amazons were comparable to those of Local Trinitario selections included as controls. The Upper Amazon clones were highly variable in establishment, yield and losses from diseases. The relationship between the performance of some of the clones and their parent seedlings is discussed.

Total yield and yield components (tuber numbers and mean tuber weights) of six local sweet potato cultivars were compared in wet and dry season crops. There were significant negative correlations between tuber number and mean tuber weight in five of the six cultivars, and positive correlations between these yield components and total yield, suggesting that cultivars may be grouped into ‘tuber number-tuber weight’ and ‘tuber weight’ types, as well as a ‘random type’ in which yield is related to neither component. Marketable yield tended to be directly related to both components, and cultivars with lower tuber numbers usually produced a higher percentage of marketable yields. The significance of these findings for sweet potato yield improvement is discussed.

Three maize cultivars, BACOA, SAW and COCA, were evaluated when intercropped with cocoyams at a density of 50 000 maize plants and 10 000 cocoyam stands ha−1. BACOA which matures in 120 days, and SAW (130 days) transmitted significantly more light to the lower canopy than COCA, which has spreading leaves and matures in 150 days. Relative yields for BACOA, SAW and COCA in pure stands were 72, 100 and 85%, respectively, while those for cocoyams in BACOA/cocoyam, SAW/cocoyam and COCA/cocoyam mixtures were 82, 58 and 54%, respectively, showing that COCA significantly suppressed the yield of cocoyam when intercropped.

Yields of a COCA type with erect leaves increased as plant density increased from 20 000 to 50 000 plants ha−1 in pure stands, while yields of COCA with spreading leaves increased as plant density increased from 20 000 to 40 000 plants ha−1 but decreased when plant population increased to 50 000 plants ha−1. When COCA with erect leaves was intercropped with cocoyams, cocoyam tuber yields were fairly stable and maize yields continued to increase significantly as plant density increased from 20 000 to 50 000 plants ha−1, whereas the yields of COCA with spreading leaves and cocoyams were greatly reduced when intercropped and when the plant population increased from 20 000 to 50 000 plants ha−1.

Low-temperature stress is an important limiting factor to tobacco growth in early spring of south China. In this study, a low-temperature-resistant agent (LTRA) was employed to examine its ameliorating effect on the inhibition of tobacco growth triggered by low-temperature stress. Results indicated that low-temperature stress of 12 °C for 6 days reduced root number and biomass of tobacco seedling by 27.4% and 24.1%, while treatment with LTRA could recover the inhibitory effect of low-temperature stress on tobacco growth significantly. The content of ascorbic acid and the activities of superoxide dismutase and catalase at low-temperature stress were 65.2%, 53.5% and 32.1% of those at normal temperature condition (26 °C), while the corresponding values with LTRA treatment were 89.2%, 88.9% and 74.2%, suggesting that LTRA treatment could enhance the activity of antioxidant enzyme and the synthesis of antioxidant compounds. Low-temperature stress increased the membrane permeability by 84.8%, while LTRA treatment recovered it by 77.4%. Furthermore, LTRA treatment contributed to increase chlorophyll synthesis and maintain the integrity of tobacco leaf structure. Effective component analysis indicated that the complex of ammonium calcium nitrate and glycine betaine was the main effective component of LTRA in maintaining membrane integrity. Its effective concentration was 1.0 g L−1. The above results suggested that LTRA could enhance the synthesis of chlorophyll, activate the activity of antioxidant enzyme, maintain the integrity of cell membrane, and thus elevate the tolerance of tobacco seedlings to low-temperature stress.

In the wheat–sugarcane rotation, which covers more than half of the growing area in subtropical India, planting of sugarcane is delayed until after the wheat harvest in April–May. This allows little time for the sugarcane to produce tillers and so results in smaller millable cane populations and yields than those from more timely (February–March) plantings. This study considers techniques such as ring and trench planting which might allow a high seed rate to compensate for reduced tillering. Yields obtained using these systems were about 20 t ha−1 greater than from the conventional flat planting method, because of a better distribution of primary shoots from the parent sett and reduced plant competition during the early stage of growth. The cost of cane production was greatest with the ring system and least with the conventional planting method but deep trenches gave the best net return.

Hardening of Coffea arabica saplings by watering cycles (WCs) might be a suitable practice to achieve higher tolerance to low leaf water potential (Ψleaf) before transplanting to the field. As a consequence, hardening could promote growth and biomass gain during the initial development of C. arabica in the field. Thus, the less interrupted initial growth in a changing environment should confer higher flowering intensity in hardened than in control plants. The aim of this work was to verify if leaf gas exchange and Ψleaf behaviour of C. arabica saplings grafted on C. canephora showed consistent alterations during hardening by WCs and if this was effective to improve vegetative and reproductive growth under field conditions. For these reasons, saplings of the Mundo Novo cultivar of C. arabica grafted on C. canephora were submitted to seven WCs over 35 days. Each WC was completed when net photosynthesis was close to zero. The pattern of leaf gas exchange, mainly stomatal conductance (gs), was modified permanently after three WCs and the new pattern of leaf gas exchange could result in a more positive water balance and less interrupted development of C. arabica saplings in the field, particularly due to permanent low values of gs. After field transplantation, hardened plants showed greater height and stem diameter, more leaves and branches, and superior biomass production in leaves, stem and roots than control plants in dry and wet periods. The number of flowers was also significantly higher in hardened than in control plants. On the other hand, similar values were found between control and hardened plants in the leaf area ratio and the shoot/root ratio. Therefore, previous hardening by WCs was effective in improving leaf gas exchange, vegetative and reproductive development under field conditions and maintained the original biomass partitioning among the main plant compartments in dry and wet periods.

Drawing on ideas advanced during the course of an international workshop, this paper reviews agricultural research priorities in the dry areas of the developing world, where economic and demographic pressures are driving a rapid intensification of production, even on very fragile lands. Current priorities for research and research funding reflect a strongly felt need, among governments and donor agencies, for rapid problem-solving to relieve poverty. In this context, traditional long-term agronomic research trials, with essentially strategic and basic objectives, are often seen as irrelevant. Yet the need to anticipate problems impending in environments where intensification is consuming the natural resource base and degrading the production potential is an urgent one. To accommodate this need to the perceptions of the different stakeholders, a new research paradigm, ‘Anticipatory Long-Term Research for Sustainable Productivity’, is proposed. It invokes a holistic approach, building a longer view and greater dynamism into traditional agronomy, enhancing ties to socio-economic and resource management disciplines, and reconciling the immediate demand for high-yielding technology with the strategic issues of sustainable production.

Field experiments conducted over 2 years to evaluate the merits of fractional application of N to hybrid maize unequivocally established its utility in circumventing leaching losses and consequently boosting grain yield. Combinations of fractional application need to be phased to minimize leaching losses and also to correspond to crop needs. Fractional application improved yields even in years when the incident rainfall was evenly distributed.

An experiment in which irrigation intervals for lucerne were dictated by four factors applied to daily evaporation from a Class A pan has been reported by Landsberg (1966). This paper discusses data from a number of subsidiary measurements made during that experiment. An extensive soil sampling programme yielded data on the effects of treatments on soil moisture content, and plant height and per cent ground cover measurements enabled detailed evaluations to be made of crop responses. Both height and ground cover were decreased by soil moisture stress. Relative turgidity was closely related to soil moisture content in the early morning, dry treatments showing more rapid recovery of turgor than those where water was kept at more adequate levels. Radiation utilization by the crop was affected by soil moisture conditions, and also apparently by temperature.

Although the groundnut and soyabean are not close taxonomic relatives they have a number of features in common. Both are polyploid (2n = 4x = 40 chromosomes) and have arisen from the domestication of wild polyploids. Polyploidy has occurred independently at least twice in the genus Arachis, while in Glycine the genus includes both tetraploids and octoploids, an unusually high ploidy level in a legume. Both crops are oilseeds although oil content varies widely between the two species, ±50% in groundnut and ±20% in the soyabean. The soyabean produces ±35% protein content of good quality whereas that of the groundnut is ±30% and less well balanced nutritionally. The soyabean originated in the Far East whereas the groundnut originated in the eastern Andes foothills (N.W. Argentina to S. Bolivia). The evolutionary changes under domestication in the soyabean are typical; the cultigen has become a compact, erect, self-supporting plant with reduced pod dehiscence and loss of seed dormancy. The evolutionary response pattern of the groundnut is similar but modified on account of its geocarpy. This necessitates the maintenance of adequate contact between basal branches of the plant and the soil for effective fruiting. Notwithstanding this, strongly ascending growth forms have become established. The greatest contrast between the two species is in photoperiod sensitivity; the groundnut is day-neutral while the soyabean is a short-day plant with genotypes varying widely in the day length tolerated without inhibition of flowering.

Two extensions to the Land Equivalent Ratio (LER) concept, the Effective LER and the Staple LER, are evaluated for an intercrop of two species. The use of different standardizing sole-crop yields in the Effective LER equation is emphasized for the formation of different comparisons between intercrop and sole-crop yields. The Staple LER for different standardizing sole-crop yields is introduced. The equivalence of the Staple and Effective LERs under certain conditions is shown and illustrated.

Infection of groundnut by pathogens causing early and late leaf spot diseases is strongly affected by accumulated daily leaf wetness periods and, in the rainy season, temperature is unlikely to severely limit infection. Earlier work relating patterns of leaf wetness to infection, was used to define a daily Wetness Index (WI) which was compared with infection on inoculated plants exposed in the crop for periods of 7 d. Infection was only severe when the 7-d WI total exceeded a value of 2.3. The proportion of leaves with one or more lesions on the main stem was used to assess the amount of inoculum in the crop. When the proportion of diseased leaves exceeded 10% and the WI total exceeded the threshold, application of a fungicide was advised. Successive sprays were separated by at least 14 d and a maximum of three sprays were applied in the growing season. Field trials showed that three sprays gave limited benefit where the disease pressure was severe, but substantial increases in pod and haulm yield were possible with only one or two fungicide applications in locations with less disease pressure.

The potential yield of wheat and the physiological basis of yield limitation in the lowland irrigated tropics was investigated in three cultivars planted at five sowing dates. Maximum grain yields were achieved by cultivars that flowered in January when the weather was coolest. The period from sowing to terminal spikelet initiation was similar for all varieties and all sowing treatments. The period from terminal spikelet initiation to ear emergence was increased when seed was sown in late November or early December rather than in October or early November. Manipulation of the sowing date in relation to the choice of cultivar had a considerable effect on grain yield.

H. M. Ishag and O. A. A. Ageeb: Rendimiento del trigo en las zonas tropicales.

Selecting high-yielding cultivars under drought is an important practice to improve crop production. Canopy temperature (T) shows a relative reliable association with grain yield. In this study, we compared the suitability of canopy T and other agronomic as well as physiological traits associated with grain yield under different water regimes. Field experiments over two seasons (2011–2012 and 2012–2013) were carried out under three water regimes, represented about 64, 76 and 89% of potential evapotranspiration, with 16 local winter wheat (Triticum aestivum L.) cultivars in each season. Results showed that cultivars with higher yield usually performed consistently lower canopy T under three water regimes, while the relationships of grain yield with other agronomic or physiological traits were more influenced by soil moisture. In addition, the relationship between canopy T and grain yield varied with different growth stages: From the time of heading to early grain filling stages, a more significant negative linear relationship (p < 0.001) existed under the three irrigation levels.

It is suggested that quite a small computer, in association with a minimal program for the analysis of variance, can be used to calculate quantities of use to the agronomic research worker beyond what he usually obtains. For example, without further programs it is possible to calculate an analysis of covariance, in which adjustment is made for some disturbing factor. It is also possible to find how much of the error variance arises from a particular plot, and to deal with situations in which data are incomplete or the yields from two plots have become mixed.

Rubber is usually cultivated for lifespan of 30 years based on the technical feasibility of managing tapping panels. For obtaining early financial benefits, there is a demand for shorter lifespan with intensified tapping. With no research conducted on this line, the present study was focussed to investigate the financial feasibility of shortening the lifespan of rubber trees through lifecycle analyses with three principal scenarios of intensified harvesting, i.e. Intensified Harvesting throughout the Total harvesting Period to obtain a part or full amount of yield lost due to shortening the lifespan (IHTP), Intensified Harvesting only during last 6 Years (IH6Y) and Intensified Harvesting at last ¼ of harvesting Period (IH¼P). In IHTP, intensified tapping to achieve 10–15% of yield loss due to shortening the lifespan was found to be effective to reduce the lifespan even up to 21 years. Market price of rubber and tree stand per hectare were found to be the critical factors determining the best lifespan particularly in IHTP. The best lifespan under IH6Y and IH¼P scenarios was in the range of 19–22 years. Agronomic, environmental and social implications in shortening lifespan of rubber are discussed.

Herbage production from twelve perennial grasses was analysed under two frequencies of defoliation. There were differences in the speed of establishment from seed, Heteropogon contortus, Pennisetum pedicellatum and P. polystachyon being most rapid. Once the grasses were established, the highest yields were obtained from Andropogon gayanus and Brachiaria brizantha and the lowest from Paspalum notatum. Yields were higher at the lower frequency of cutting. There were large differences in production throughout each year, with yields during winter and the dry season (November to April) only about one-tenth of those obtained in the rainy season. A. gayanus, B. brizantha, Chloris gayana and Dichanthium caricosum gave higher yields than other species during winter. Variations in yield between species could generally be ascribed to variations in the extension of leaf area, although some species maintained high net assimilation rates during unfavourable growth periods.

Mixing of phosphate fertilizer with farmyard manure (FYM) is a simple technique for optimizing phosphorus (P) availability and then improving the productivity of wheat (Triticum aestivum) grown in alkaline calcareous soils. Diammonium phosphate (DAP) and phosphoric acid (PA) were applied to soil at 36 mg P kg−1, either as sole or after amending 1-g P fertilizer with 2-g FYM (1:2, w/w basis). After 45-day incubation, concentration of P ions in the soil solution (Cp) and exchangeable P present in soil solid (E-value) were determined to evaluate the amount of total plant-available pool. The FYM-amended fertilizers, i.e., PA+FYM and DAP+FYM, showed higher E-values, i.e., 114 and 97 mg kg−1 soil, respectively. Similarly, PA+FYM exhibited the highest proportion of P derived from fertilizer (Pdff = 51.5%) and induced the highest P uptake by wheat seedlings (L-value = 72.1 mg kg−1). Consequently, PA+FYM and DAP+FYM treatments caused higher grain yield and P-use efficiency. The regression analysis revealed strong and positive correlation between L-value and grain yield (r = 0.86), biomass production (r = 0.84) and P-use efficiency (r = 0.87) by wheat crop. Results suggested that FYM-amended inorganic P fertilizer can be a promising technique to optimize supply of P from soil, improve efficiency of inorganic P fertilizers, and improve wheat yield in alkaline calcareous soils.

Hypocotyl length in groundnut is a function of sowing depth. In field experiments deep sowing increased the mass of hypocotyl but decreased that of roots, pods and haulm. Few nodules were formed on the hypocotyls of plants from shallow sown seeds (4–5 cm deep). More hypocotyl nodules occurred on Virginia types when deep sown but the number and activity of nodules on the roots decreased. Nodules on the hypocotyl appeared later and fixed less nitrogen than root nodules. Although hypocotyl nodules fixed nitrogen during the later stages of plant growth, this activity could not compensate for the loss in nitrogenase activity due to deeper sowing. Deeper sowing also resulted in decreased pod yields.

Scarcity, lack of access, and ineffective and inefficient use of water in Nkayi District, Zimbabwe, threaten agricultural production. The purpose of this study is to augment understanding of opportunities to increase livestock water productivity (LWP) in Nkayi District by taking into account key differences in the capacities, opportunities, and needs of women and men. There are two important types of female-headed households, de facto and de jure. The results from this study showed that male-headed and de facto and de jure female-headed households share much in common. They all had similar areas of cropland and access to education, finances, veterinary and extension services, and transportation and markets. Households of all types had similar herd sizes. All were desperately poor with incomes much less than a dollar a day. To rise out of poverty, the knowledge, skills and effort of all household heads will be needed. In spite of severe poverty, household heads of all types are literate and have sufficient education that can help enable adoption of intervention options that can lead to increased agricultural production and improved livelihoods. The results also showed that major differences exist in terms of the roles of men and women in ownership, management and decision making related to livestock keeping and animal production. Men clearly dominate in both ownership and decision making even though women play a major role in animal management. Only in de jure female-headed households were women more likely than men to own cattle and goats. They were also more likely to be involved in farming as a primary livelihood activity. Surprisingly, men were more likely to be involved in animal management in these de jure female-headed households. Women were also excluded from water users' and livestock producers' associations although a minority of men was members. By not involving the already-developed capacity of women, the community loses out on a significant opportunity to increase LWP and animal production more widely. Greater inclusion of women in decision making will be an important part of future efforts to improve livelihoods through livestock development.