Line sowing of jute has been advocated by some workers for the past 40 years as being more productive than the traditional broadcast method. But most cultivators still prefer broadcast sowing. A comparative study employing identical management practices showed that there is no significant difference in fibre yield per unit area between the two sowing methods. Under similar population pressures self-thinning is greater in line sown than in broadcast crops. Thus, provided similar seed rates and cultural conditions are maintained, farmers may use either sowing method.

P. Palit, A. C Bhattacharyya y B. K. Samanta: Re-evaluación de los efectos de la siembra al voleo y en lineas sobre el rendimiento defibra del yute.

Where ancient agricultural sites are brought back into cultivation, using new forms of irrigation, cotton often grows badly in the first few seasons. A theory is developed to account for these failures, and it is shown that heavy irrigations before planting not only produce better crops but may also economise in water.

A variety of established tools are available for agricultural sustainability assessment at global, regional, and farm geographical scales. However, no assessment has been reported in research literature to indicate their ability to provide insights about the most sustainable cropping system at plot level or experimental unit. Despite the environmental and social importance of soil in agricultural systems, many of the sustainability assessments use few or no indicators related to soil properties or processes. Hence, we propose a sustainability assessment methodology oriented to soil-associated agricultural experiments (SMAES) by defining its parameters through simulations and testing the methodology with real data from a fertilization tomato experiment with five treatments: chemical control (CR); organic control (OR); and organic:chemical ratios (OR) of 25:75, 50:50, and 75:25. The distance from the maximum, principal component analysis, and product of weighted indicator techniques were chosen for normalization, weighting, and aggregation in a single index process, respectively. Applying the SMAES methodology, the sustainability level of the treatments followed this sequence: CR (0.95) > O25:C75 (0.73) > O50:C50 (0.60) > O75:C25 (0.55) > OR (0.45). The proposed SMAES methodology allows soil researchers to define the best treatment through the interaction of the environmental, social, and economic dimensions of agricultural systems.

Rice productivity is limited by many pests, especially Pomacea spp. in Southeast Asia. Pomacea spp. damage to rice depends on sowing methods, flooded conditions, and snail densities in the field. Therefore, this study aims to evaluate the effect of different sowing methods, water levels, and snail density (1, 2, and 3 snails per plot) on the damage potential of Pomacea maculata and Pomacea canaliculata to rice and its yield. Both species caused complete loss of crop in direct seeding and 14 days old transplanted rice. The least damage by both species was recorded in 21 and 28 days old transplanted rice with no further damage after week five. Irrigation and snail density also influenced damage whereby highest damage was recorded in rice grown with 5 cm water level in comparison to 2 cm. At 2 cm water level, damage by various snail densities was trivial. However, in 5 cm water level, damage increased with the increasing snail density and the highest damage was observed at three snails per plot of either species. No difference in inflicted damage to various treatments was observed between two species, suggesting their equal damage potential on rice. Meanwhile, rice yields in 2 cm water level treatments were compatible with 5 cm control treatment. The least yield was recorded in treatments with three snails per plot of either species at 5 cm water level. Understanding the effect of sowing method and suitable water level is important as it can be further incorporated into rice cultivation practices to reduce damage of apple snails and ensure a high yield during harvest.

Hand-pollinated pods of the Crin Elite establishment cocoa progeny C77 X C23 showed that pod maturity, based on pod age, significantly affected bean viability as well as leaf area, leaf number, plant height and plant girth of the seedlings produced. Beans extracted from immature unripe cocoa pods only 15 weeks from hand-pollination were more than 50 per cent viable and produced seedlings vigorous enough for transplanting to the field after 20 weeks in the nursery compared with beans from 25-week-old normal, mature-ripe cocoa pods. Loss by black pod disease (Phytopthora palmivora Butl) could therefore be avoided and time of waiting for pods to attain normal maturity and ripening saved, by early harvesting.

The response of Italian ryegrass (IRG) to nitrogen fertilization, irrigation frequency and harvest interval indicated that management of nitrogen and water is the determinant of productivity under semi-arid northern Mexican conditions. Where water is non-limiting the effects of harvest interval can be eliminated. A soil moisture balance model indicated the inadvisability of seeding IRG in sandy soils if water is a scarce resource because of the high frequency of irrigation that would be required. The seeding (September) and late production (April) periods were identified as critical in regard to irrigation need and limiting in terms of the area that it would be possible to seed.

The perennial grass Pennisetum polystachyon was grown alone or in mixture with the indigenous legumes Atylosia scarabaeoidesand Clitoria ternata and the exotic species Calopogonium mucunoides, Centrosema pubescens and Stylosanthes gracilis. Only the last two persisted for more than one or two years. Mean annual yield from the mixture containing Centrosema was 61 to 65 q./ha., of which 20 per cent was legume herbage. The protein content of grass was about 3 to 6 per cent and of legumes 10 to 14 per cent. Mixed swards produced as much protein as in a previous experiment where pure swards of Pennisetum polystachyon received 44. kg./ha. of nitrogen in fertilizer form. Soil nitrogen increased under the Centrosema mixture and yields from the mixture increased during the experiment. Yields of grass herbage from the mixtures were generally lower than those of the grass swards. The reduction in yield of grass grown in mixed swards was mostly due to decreases in the area of foliage rather than to reductions in net assimilation rate.

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.

The West and Central Africa Collaborative Maize Research Network (WECAMAN) was established in 1987 to strengthen the capacity and capability of national programmes of West and Central Africa (WCA) to tackle regional constraints to maize production. The Network created several mechanisms for implementing, monitoring and evaluating maize research and development activities, including research project development and implementation, attendance and quality of paper presentation at technical conferences organized by the Network, scientific monitoring tours, consultation visits, mid-term reviews, and end-of-project reviews and impact assessment. WECAMAN's approach to the system of allocating research responsibilities and competitive grants resulted in increased research efficiency and the generation of sustainable technologies that have catalysed increased maize production in the region.

In a 4 × 4 × 4 NPK field experiment with coconut on a sandy soil, N increased girth, height and leaf production during the pre-bearing period, but phosphorus (up to 6½ years) and K (up to 3½ years) had no effect on any vegetative growth parameters. The rates of fertilizers for optimum copra and nut yield (13 to 16 years) were 0.35, 0.73 and 0.64 kg N, PO and KO/palm/ year respectively. The high P requirement was due to the low solubility of the saphos phosphate in these sandy soils. A positive N × P interaction was also observed.

The functional distribution of root activity was determined by selective placement of 32P at fixed positions from the base of the plant in five- and six-year-old acid lime (Kagzi Kalan) on Kama Khatta rootstock. Maximum recovery of radioactivity was observed within a 40 cm radius of the plant base and at depths of 24 cm in 1988 and 16 cm in 1989. Most root activity (75–80%) was confined within a radius of 80 cm and a depth of 16–24 cm. Application of fertilizer within this zone is therefore recommended for maximum utilization by the crop.

Actividad de las raíces en la lima acida