The profitabilities of three land use systems in the humid zone of southwest Nigeria are compared using a capital budgeting procedure combining on-station and on-farm experimental data. The systems are: non-alley farming with fallow; alley farming with fallow; and continuous alley farming. The results indicate that: continuous alley cropping is more profitable than non-alley or alley cropping with fallow; short fallowing in alley cropping reduces the rate of mining soil fertility and thus helps preserve future productivity; alley farming with small ruminants enhances the profitability of alley systems and increases their advantage over the non-alley system; and alley systems remain profitable even when terminal clearing costs are internalized in the current project cycle.

Twenty one accessions of yam bean (Pachyrhizus Rich. ex DC.) were tested in yield trials under short day conditions in Tonga, South Pacific. Fresh weight tuber yields ranged from 5.3 to 72.0 t ha−1, dry matter content from 8.0 to 20.8% and dry matter yields from 1.20 to 8.57 t ha−1. Crude protein content of peeled tubers varied between 5.1 and 9.8% of dry matter, yielding 71–540 kg ha−1 of crude protein. Varietal variation in leaf defoliation by the rose beetle, Adoretus versutus Har., was noted.

Grain barley was grown either continually or in rotation with fallow in a 12-year experiment. Annual rainfall ranged from 120 to 297 mm. As the water requirement of the crop is 240 mm, growth in most seasons occurred under water stress. The amount of water conserved under fallow was only significant (75–100 mm) in three of the 12 years and only once did the water conserved increase barley yield in the following year. The total grain yield over the experimental period was twice as high in the barley–barley sequence as in the barley–fallow sequence.

Cultiuo continuo de cebada o después de barbecho

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

Root/shoot relations of two cultivars of pearl millet (Pennisetum glaucum) were studied on a sandy soil at Sadore in Niger using a wet excavation method. For the first 10 days after emergence (DAE), the length of the seminal root showed an exponential growth rate while plant height increased more or less linearly. The maximum rooting depth for millet was 168 cm and the maximum number of root axes and primary laterals, 172 per plant. Root length continued to increase up to 75 DAE, the maximum length exceeding 5000 cm per plant. The proportion of total day matter accumulated in the roots decreased from 30% in the early stages to less than 20% by maturity. The wet excavation method is a promising technique for the rapid removal of intact root systems of pearl millet from the sandy soils of the Sahel.

Pearl millet is a staple cereal cultivated mainly by subsistence farmers on 14 million ha of the West African semi-arid tropics. Increasing pressure on the land has reduced the length of the fallow periods, which are necessary to restore soil fertility, resulting in declining yields. To investigate ways of reversing this decline, three systems combining phosphorus fertilizer application, improved varieties of millet and cowpea, and improved agronomic practices were compared with the traditional millet–cowpea intercrop system in a three year experiment. The most productive system involved the rotation of fertilized millet and cowpea. Pre-sowing tillage increased hay and fodder yields in all the improved systems. The application of fertilizer increased the amount of available phosphorus in the soil. Soil pH declined somewhat in all treatments, although the initially low soil organic matter did not change.

Twenty-one genotypes of pigeonpea were evaluated for their alley cropping potential in two environments differing in soils and climate on the island of Oahu/Hawaii. All entries were planted in hedgerows in August 1988 and were cut 1 m above ground level 229, 290 and 342 days after sowing. Dry matter yields for seven selected genotypes from the three cuttings combined ranged from 691 to 4083 g m−2, with significant differences between genotypes and significant genotype × environment interactions. Genotypes rarely combined more than two desirable alley cropping characters, suggesting a distinct role for selected genotypes in different alley cropping environments. None of the effects influencing growth and yield were constant over levels of the other factors studied, indicating a need for multi-locational testing and standardized sampling intervals in future genotype evaluations with perennial pigeonpea.

Evaluación de genotipos de Cajanus cajan para cultivo en hileras

Crop simulation models have been proposed as tools for the transfer of technology in less developed countries. Using a validation exercise as a framework for evaluation, this study looked at the ease of use of a simulation model in a small African research station. Although the model did not accurately predict grain yield of the local maize hybrid, the procedure did highlight some of the problems involved in applying the model. The constraints to the use of such models at small research stations are discussed and improvements that could facilitate model use are suggested.

Uso de model de cultivo para la investigación en Africa

An evaluation of methods for replacing established uncapped, multiple stem, arabica coffee cv. French Mission with cv. Ruiru 11 arabica hybrid in the field was carried out at Ruiru, Kenya. When Ruiru 11 was raised on a single stem using the hedgerow system, a mixed stand of Ruiru 11 and French Mission gave the largest mean yields of clean coffee. The next largest yields were obtained by the complete replacement of French Mission with Ruiru 11 grown at a spacing of 2 × 1.5 m and trained on a single stem system. However, in economic terms, replacing the established coffee partially or sequentially with Ruiru 11 trained on a single stem proved to be the best method.

Métodos de reemplazo de café

The impact of a 20-year-old cashew plantation on a forest soil was evaluated by comparing the properties of soil under cashew with that under an adjoining logged rain forest. The levels of organic carbon, nitrogen, exchangeable calcium and magnesium, and available phosphorus were similar under logged forest and cashew, suggesting that organic matter and nutrient cycles in a cashew plantation are similar to those in a logged rain forest and that cashew has no significant adverse effect on soil organic matter and nutrient status.

The effects of cropping system, nitrogen application and harvesting stage on the quantity and quality of the forage produced by Sudan grass-lablab mixtures were studied in central Sudan. Mixing increased the number of tillers plant-1 of Sudan grass and the plant dry weight of both crops. Application of nitrogen increased the number of tillers and dry weight plant-1 of Sudan grass but had no significant effect on the growth parameters of lablab. Growth parameters of both crops were appreciably increased by harvesting at the milk-ripe stage of Sudan grass. The largest total dry matter yield was obtained from a mixture of 20 kg Sudan grass and 40 kg lablab ha-l, but the largest protein yield was obtained from sole lablab.

Nitrógeno en combinaciones de sorgo sudanés y Lablab purpureus

The after effects of three years' continuous cropping with sole millet, sole cowpea or a traditional millet/cowpea intercrop were compared using five levels of nitrogen fertilizer. The continuous sole cowpea system had reduced the carbon to nitrogen ratio more than the continuous sole millet or the traditional intercrop. The test crop millet yielded much more, and its uptake of nitrogen and phosphorus was greater, when it followed sole cowpea than when it followed sole millet or the traditional millet/cowpea intercrop. The three years' continuous sole cowpea had an effect equivalent to the application of 205 kg N ha−1 on the test crop of millet. It also caused the greatest reduction in Striga infestation in the test crop. It is therefore recommended that cowpea cultivation be increased in the Sahel.

Non-destructive methods are described for estimating annual above-ground dry matter production by the coconut palm, Cocos nucifera. Leaf dry weight is estimated from the cross-sectional area of the petiole. Trunk dry weight increment is estimated from the volume increment, and a function relating trunk density to palm age. Husk and shell dry weights are estimated from air-dry weights; copra dry weight is measured after oven drying. The weight of inflorescence stalks is small, and is ignored. Leaf area can be estimated from measurement of the length and width of a sample of leaflets. These methods have been applied to two coconut variety trials, and show significant differences between varieties in crop growth rate and harvest index. The trend of leaf area with palm age is described for two varieties and the hybrid between them.

Medida de la producción de materia seca en el cocotero

The influence of liming and method of cultivation on the dry matter yield, botanical composition and seedling density of a rainfed pasture grown in a Mediterranean environment from a commercial seed mixture based on subterranean clover was investigated. Liming resulted in a 2.5-fold increase in pasture dry matter yield. Yields were greater when the soil was scarified before sowing than when it was ploughed, and when the lime was spread after cultivation rather than before. Liming and scarifying increased the proportion of sown species (subterranean clover, white clover and tall fescue) and reduced the proportion of native species and bare ground. Subterranean clover seedling density was higher after scarifying than after ploughing.

Uso de cal en pastos mediterráneos regados por precipitaciones

A field experiment was conducted on a highly alkaline soil (pH 10.6, exchangeable sodium 95%) to compare biological reclamation using Leptochloa fusca with chemical reclamation using gypsum. Rice gave satisfactory yields in the first year of gypsum application but sorghum and Sesbania gave extremely poor yields. The yield of Leptochloa was not affected by gypsum application. Trifolium resupinatum yielded more than T. alexandrinum when sown in the winter season. The green forage yield of sorghum was greatest when the sorghum followed Leptochloa grown for two years, with the harvested grass allowed to decompose on the site. The results show that biological reclamation with Leptochloa is a good substitute for chemical reclamation with gypsum.

The effect on Coffea arabica cv. Ruiru 11 of training the trees on a single or two stem system at planting densities of between 1600 and 4800 trees ha−1 during the first production cycle after establishment was studied at three contrasting sites in Kenya. Training tree growth in the two stem system significantly depressed yields from the first two crops at all sites, irrespective of plant density, but yields caught up with the production levels of the single stem system faster in the wetter than in the drier zone. Yields of clean coffee increased with tree density up to 4000 trees ha−1 at all sites, irrespective of tree training method, but increased more slowly at populations of more than 4000 trees ha−1, especially in the drier zone. The proportion of large, grade A, coffee beans was not significantly influenced by the treatments studied.

Yields of intercropped cotton and groundnuts grown on alternate ridges 75 cm apart were compared in areas of high (more than 1000 mm a year) and low (less than 800 mm a year) rainfall and in rainy seasons with a low and high frequency of drought periods. There was no advantage from intercropping in the low rainfall area but in the high rainfall area land equivalent ratios of about 1.4 were obtained, confirming that intercropping is more suited to wet conditions. These high land equivalent ratios were associated with enhanced yields per plant in the cotton and unsuppressed yields per plant in the groundnuts, suggesting that a crop such as cotton, which both tolerates a wide range of population density and has a late-developing leaf canopy, may be particularly well suited to intercropping.

Cultivo simultáneo de algodón y chufa en zonas con altas y bajas precipitaciones en el este de Zambia

Beusani is a rice crop management system practised in rainfed lowland areas of eastern India whereby rice is dry-seeded, then wet-ploughed at 30–50 days after emergence and the land levelled by drawing a board across the field. Field experiments showed that beusani enhances rooting, especially in shallow soil layers, as a result of reduced penetration resistance. Although beusani reduced weed biomass by 38%, it was not as effective as application of herbicide followed by hand weeding, which reduced biomass by 87%. Yields were directly related to weed control, so beusani treatments did not yield as much as the herbicide plus hand weeding treatments in these experiments.

Intercropping with a spreading type of cowpea was studied as a technique for the control of Striga hermonthica on sorghum in northern Cameroon. Alternate rows of cowpea did not reduce Striga density but planting the cowpea and sorghum in the same row, in the same or alternating hills, reduced Striga density and numbers of Striga per sorghum stand. Yields of sorghum grain in the same-row planting treatments were not significantly less than sole sorghum yields, and 200 to 700 kg ha−1 of cowpea grain was produced. Alternating stands of sorghum and cowpea within the same row gave the best yield of sorghum and greater reduction of Striga. Production of mature Striga with capsules decreased with increasing cowpea ground cover, so that while cowpea may not reduce Striga emergence, it may hinder Striga development, possibly reducing the Striga seed bank over time.

Four tillage treatments were applied to soil on which wheat was to be sown in 1988/89 after pastures of two annual medics, Medicago rigidula and M. polymorpha, had been established in 1987/88. Germination of the medics was monitored in the following year (1989/90) when halfof each plot was sprayed to prevent further seed set. M. polymorpha produced more seed in 1987/88 and three times more regenerated seedlings in 1989/90 than M. rigidula. Regeneration and winter herbage yields of both medic species were least after deep ploughing. Seedling numbers were less in 1990/91 than in the previous year but seedling numbers of M. polymorpha were sufficient to sustain the cereal-pasture rotation except after deep ploughing. Both medics germinated promptly soon after the first effective rains in December 1989, but the first germination in 1990/91 was on 24 November, with three subsequent germinations, the last in early February. About half (40 to 50%) of pods remained in the top 5 cm of soil, except after deep ploughing when only 28% remained near the top. The seeds in the top layer lost their hard-seededness more rapidly than those buried more deeply. M. polymorpha was softer seeded than M. rigidula. The results suggest that deep ploughing, as commonly used in west Asia and north Africa, is unsatisfactory for cereal-pasture rotations.

Regeneración de alfalfa en Siria