The principal objections to the proposition that organic agriculture can contribute significantly to the global food supply are low yields and insufficient quantities of organically acceptable ...fertilizers. We evaluated the universality of both claims. For the first claim, we compared yields of organic versus conventional or low-intensive food production for a global dataset of 293 examples and estimated the average yield ratio (organic:non-organic) of different food categories for the developed and the developing world. For most food categories, the average yield ratio was slightly <1.0 for studies in the developed world and >1.0 for studies in the developing world. With the average yield ratios, we modeled the global food supply that could be grown organically on the current agricultural land base. Model estimates indicate that organic methods could produce enough food on a global per capita basis to sustain the current human population, and potentially an even larger population, without increasing the agricultural land base. We also evaluated the amount of nitrogen potentially available from fixation by leguminous cover crops used as fertilizer. Data from temperate and tropical agroecosystems suggest that leguminous cover crops could fix enough nitrogen to replace the amount of synthetic fertilizer currently in use. These results indicate that organic agriculture has the potential to contribute quite substantially to the global food supply, while reducing the detrimental environmental impacts of conventional agriculture. Evaluation and review of this paper have raised important issues about crop rotations under organic versus conventional agriculture and the reliability of grey-literature sources. An ongoing dialogue on these subjects can be found in the Forum editorial of this issue.
The objective of this work was to study the yield performance and to determine the gross income of arracacha (Arracacia xanthorrhiza Bancroft), cultivar Amarela de Carandaí, grown in monoculture as ...well as in intercropping with the Japanese bunching onion (Allium fistulosum L.), cultivar Todo Ano (A-JBO) and parsley (Petroselinum crispum (Mill.), cultivar Lisa Preferida (A-P). Arracacha and the Japanese bunching onion were vegetatively propagated, while parsley was propagated by seeds. The Japanese bunching onion was first harvested 87 days after the planting (DAP), with resprouts harvested 154 and 212 DAP. Parsley was first harvested 105 days after the sowing (DAS), and, resprouts, 171, 212, and 268 DAS. Arracacha was harvested 268 DAP. At the harvest carried out 212 DAP, the Japanese bunching onion plants in monocrop significantly exceeded those in intercropping in 1.73 cm height and 0.99 t ha-1 commercial fresh mass (CFM). In parsley, the CFM yield in monocrop significantly exceeded the intercropping figures in 0.63, 0.66, and 0.72 t ha-1 at harvests carried out respectively 171, 212, and 268 DAS. Plant height and CFM of the Japanese bunching onion and parsley increased after every new harvest, except in parsley, for plant height 171 DAS and CFM 268 DAS. No significant differences were found in any of the evaluated characteristics when arracacha as single crop was compared to the A-JBO intercropping arrangement. Nevertheless, the A-P intercropping arrangement significantly reduced all characteristics in relation to the other systems, except for yield of non-commercial arracacha roots. A-JBO intercropping arrangement was viable (LER = 1.49) and therefore may be employed by farmers. A-P intercropping, on its turn, was unfeasible (LER = 0.97).
Este trabalho teve como objetivo estudar o desempenho produtivo e determinar a renda bruta obtida a partir do cultivo da mandioquinha-salsa (Arracacia xanthorrhiza Bancroft), cultivar Amarela de Carandaí, em monocultura e consorciada com cebolinha (Allium fistulosum L.), cultivar Todo Ano (MC), e com a salsa (Petroselinum crispum (Mill.), cultivar Lisa Preferida (MS). A propagação da mandioquinha-salsa e da cebolinha foi feita através de mudas, enquanto a salsa foi propagada por sementes. A cebolinha foi colhida 87 dias após o plantio (DAP) e, as rebrotas, 154 e 212 DAP. A salsa foi colhida 105 dias após a semeadura (DAS) e, as rebrotas, 171, 212 e 268 DAS. A mandioquinha-salsa foi colhida 268 DAP. Na colheita realizada 212 DAP, as plantas de cebolinha em cultivo solteiro superaram estatisticamente aquelas consorciadas em 1,73 cm de altura e 0,99 t ha-1 de massa fresca comercial (MFC). Na salsa, as produções de MFC em monocultura superaram estatisticamente em 0,63, 0,66 e 0,72 t ha-1 a produção do consórcio nas colheitas realizadas 171, 212 e 268 DAS, respectivamente. As plantas de cebolinha e salsa tiveram valores maiores para altura e produção de MFC nas colheitas feitas após cada novo corte, exceto em salsa, para a altura de planta 171 DAS e MFC 268 DAS. Não houve diferenças significativas em nenhuma das características avaliadas entre a monocultura de mandioquinha-salsa e o consórcio MC. Já o consórcio MS apresentou, com exceção da produção de raiz não-comercial de mandioquinha-salsa, resultados inferiores aos demais arranjos de cultivo avaliados. O consórcio MC foi considerado viável (ERA = 1,49) e pode ser utilizado pelos produtores de hortaliças. O consórcio MS, por sua vez, foi inviável (RAE = 0,97).
The paper summarizes the present state of statistical methods in agricultural research into intercropping, i.e. the growing of two or more crops together. Designs that have been used in intercropping ...experiments are reviewed. Important statistical considerations for the design of intercropping experiments are discussed and suggestions for improved design given. Available methods of analysis are illustrated with numerical examples and the advantages of each are discussed. Finally, possibilities for further statistical research are outlined.
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