Mechanical and cultural strategies to control Cirsium arvense

Infestation with Cirsium arvense in organic cropping is an increasing problem in many parts of Europe. Non-chemical management strategies against C. arvense based on cultivation tactics and/or different cutting regimes have acquired very little attention for years. This study presents results from four experiments, undertaken under organic growing conditions, on the effects of repeated mowing or hoeing during the first part of the growing season used in combination with competition from a suppressive crop (grass white-clover mixture and red clover). The strategies were mainly aimed at diminishing the regenerative capacity of C. arvense and effects were thus measured in the subsequent year in spring barley. In general, number of passes of mowing and hoeing linearly reduced the amount of aboveground C. arvense biomass in the subsequent year. Increased competition induced by the competitive crops further reduced C. arvense biomass. Differences in barley yield were explained by the amount of C. arvense biomass in the two experiments, while strong confounding effects from Elymus repens infestations occurred in the other two experiments. Our results suggest that the strategies studied are likely to increase crop yield and that an acceptable level of C. arvense control can be achieved within one growing season only

Características químicas de solo e rendimento de fitomassa de adubos verdes e de grãos de milho, decorrente do cultivo consorciado Soil chemical characteristics and green manure yield in a corn intercropped system

A adubação verde é uma das formas de aporte de matéria orgânica ao solo. O sistema de cultivo consorciado de culturas pode ser uma alternativa para aumentar a reciclagem de nutrientes e melhorar a produtividade. Para avaliar o sistema consorciado de adubos verdes com o milho, foram estudadas as características químicas do solo, a produção de matéria seca, a composição mineral de adubos verdes e o rendimento de grãos de milho, num experimento realizado em campo, entre 1995 e 1997, em solo classificado como Nitossolo Vermelho eutrófico. O milho foi semeado no espaçamento de 90 cm nas entrelinhas, perfazendo, aproximadamente, 50.000 plantas por hectare. Os tratamentos constaram de quatro espécies de adubos verdes: mucuna anã [Mucuna deeringiana (Bort.) Merr], guandu anão (Cajanus cajan L.), crotalária (Crotalaria spectabilis Roth) e feijão-de-porco (Canavalia ensiformis L.) e um tratamento-testemunha, sem cultivo consorciado. Essas espécies foram semeadas sem adubação, no meio da entrelinha, em duas épocas: simultânea ao milho e 30 dias após. O delineamento experimental foi o de blocos ao acaso em parcelas subdivididas, com quatro repetições. O feijão-de-porco apresentou maior produção de fitomassa e acúmulo de N, P, K, Ca, Mg e S. No primeiro ano de cultivo, o rendimento de grãos de milho não foi influenciado pelo cultivo consorciado com adubos verdes; no entanto, no segundo, a produção foi beneficiada pelo consórcio com feijão-de-porco.<br>Green manure is one way of supplying organic matter to soil. The mixed cultivation of crops may be an alternative to increase nutrient cycling and to improve productivity. To evaluate intercrops of green manure and corn, soil chemical characteristics, green manure dry matter production and its mineral composition and corn yield were determined in a field experiment carried out between 1995 and 1997 on an Aleudalf Soil in Piracicaba, state of São Paulo, Brazil. Corn was sown in rows spaced 90 cm apart to obtain approximately 50,000 plants per hectare. The treatments consisted of four green manure species: dwarf mucuna [Mucuna deeringiana (Bort.) Merr], dwarf pigeon pea (Cajanus cajan L.), crotalaria (Crotalaria spectabilis Roth), jack bean (Canavalia ensiformis L.), plus a control without green manure. Green manure species were sown without fertilizer application in a single row in-between the rows simultaneously with corn or 30 days after corn sowing. The experimental design consisted of randomized blocks in split plots and four replicates. Jack bean produced most phytomass and accumulated the highest amounts of N, P, K, Ca, Mg, and S. In the first year of cultivation, the corn yields were not affected by the intercropped cultivation with green manure, but in the second year the yield was highest when corn was intercropped with jack bean