Integrated pest management (IPM) in rice has been mainly applied to irrigated, lowland paddy rice ecosystems which generally use more inputs and have higher yields ha−1 than rainfed ecosystems. Large scale implementation of IPM was stimulated in the 1970s in several Asian countries by pest resurgences resulting from indiscriminate insecticide use. Legislation has been enacted in at least five countries to support IPM and by 1992, approximately 0.05% of Asian farmers had received training in IPM. In at least two countries, adoption of IPM as national policy has resulted in large savings from reduced importation of pesticides with no reduction in total rice output or productivity. The inter-country programme on rice IPM of the Food and Agriculture Organization (FAO), the United Nations, the International Rice Research Institute and national programmes have all contributed to promoting rice IPM. Host plant resistance, deployed with location-specific cultural practices that conserve natural enemies, remains the basis for sustainable, low-cost rice IPM. Thresholds, monitoring and forecasting systems have little or no impact on farmer practice in the tropics; farmer group learning appears to be the most effective way towards IPM adoption.

Manejo integrado de plagas en el arroz

Changes in seed quality were monitored during seed development and maturation in three genotypes of soyabean (Glycine max), the USA cv. Bossier, the Indonesian line TGm 737p, and their cross TGx 536–02D in a controlled environment of 30°/20°C (day/night temperatures). The capacity of seeds to germinate following desiccation and their potential longevity increased after the end of the seed-filling phase. Potential longevity reached a maximum close to harvest maturity (that is, when seed moisture content had declined naturally to 14–15%). The subsequent decline in potential longevity in all three genotypes was quantitatively similar to that predicted in post-harvest air-dry seed storage in similar environments, but was far less in TGm 737p than in the other two genotypes as a consequence of the lower moisture content of its mature seeds. These findings contradict the previously well-established hypotheses that seed quality in soyabean is maximal at the end of the seed-filling phase and that viability and vigour begin to decline immediately thereafter. They also infer that the desirable seed longevity characteristics of the Indonesian line TGm 737p may not have been successfully incorporated into the cross TGx 536–02D.

Calidad y desarrollo de similla en la soja

Several parameters of seed vigour were monitored during seed development and maturation in three contrasting genotypes of soyabean (Glycine max)— the USA cv. Bossier, the Indonesian line TGM 737p, and the cross between these two parents TGx 536–02D—grown in three different temperature regimes. Evidence of a decline in seed quality in the pre-harvest environment was seldom detected until harvest maturity, when seed moisture content had declined naturally to 14–15%. Atypically, an increase in the susceptibility of freshly-harvested shelled seeds to imbibition damage was detected before harvest maturity for cv. Bossier in the two warmer regimes. Seeds of cv. Bossier were also far more vulnerable after harvest maturity to pre-harvest deterioration in the warmer environment than the other two genotypes. From these results and those from two earlier studies, it would appear that the main seed quality characteristic of TGm 737p that has been incorporated successfully into the cross is resistance to soaking damage, rather than enhanced air-dry seed storage longevity per se.

Desarrollo y vigor de la semilla en la soja

Following a survey of fertilizer use on farmers' barley fields in northern Syria and very positive results from barley fertilizer trials on ICARDA research stations, a programme of researcher managed trials on farmers' fields indicated considerable potential for yield increase from the use of nitrogen and phosphorus fertilizers across a range of environments. It was then necessary to test and demonstrate the effectiveness of fertilizers in farmers' hands. A researcher managed trial (RMT) and a farmer managed trial (FMT), with similar fertilizer treatments, were compared over the winter cropping season on each of 10 on-farm sites in 1987/88 and 20 sites in 1988/1989. Despite large differences in rainfall between the two seasons (means across sites, 422 mm in 1987/88 and 174 mm in 1988/89), yield responses to fertilizer were similar in both seasons, with only marginal yield differences between researcher and farmer managed trials. Crop sequence had no effect on the pattern of fertilizer response in either type of trial. Once the effectiveness of fertilizers had been tested in farmers' hands, demonstration trials were conducted in the following two years to transfer the technology to farmers in the barley growing areas of northern Syria.

Ensayos conducidos por agricultores e investigadores en Siria

This paper addresses the issue of genotype by environment (G × E) interaction in relation to the distribution of germplasm from international to national breeding programmes. Theoretical aspects of G × E interaction and of the selection versus the test environment are reviewed. The importance of specific adaptation to maximize yield and yield stability under stress conditions is highlighted in barley and lentil. We conclude that repeated cycles of selection at a few sites have a high probability of reducing the frequency of genotypes specifically adapted to environmental and/or agronomic conditions not represented at those sites. Therefore a wider and earlier devolution of the selection work done by International Agricultural Research Centres (IARCs) to plant breeders in national programmes will increase the chances of exploiting positive G × E interactions. It will also address the needs of small, resource-poor, subsistence farmers and reduce the danger of narrowing genetic diversity within crops and regions. This is an efficient way of making breeding programmes in less developed countries more self-reliant, which is a major objective of International Agricultural Research Centres.

Programas internacionales de reproducción

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

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

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

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

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

The effect of simulated drought on the germination of Striga hermonthica and Alectra vogelii was studied in growth cabinets. Drought stress was applied either during the preconditioning of the seeds or at the time of application of the germination stimulant. The response of these weeds to a range of alternating day/night temperatures during germination and their attachment to the host plant was also investigated using root chambers. During the preconditioning period S. hermonthica was not sensitive to variation in osmotic potential between 0 and −1.5 MPa but A. vogelii required longer preconditioning periods at −1.2 and −1.5 MPa. The germination of both parasites was significantly reduced by increasing the osmotic potential of the stimulant. Optimum day/night temperatures for germination and attachment of S. hermonthica were 30/20° and 35/25°C, and of A. vogelii 25/15° and 30/20°C. Deviation in temperature from the optimum significantly reduced the germination and attachment of both parasites. The results show that S. hermonthica is more adaptive to adverse climatic conditions of increased osmotic potential and extreme temperatures than A. vogelii.

Efecto de la sequia y la temperatura en malezas parasiticas