Light Transmittance, Soil Temperature, and Soil Moisture under Residue of Hairy Vetch and Rye

Abstract

Cover crop residue on the surface of soils in no-tillage systems can suppress weed emergence and growth. Although allelopathy often is invoked to explain weed suppression by residue, physical alterations of the seed environment could be important as well. This experiment was conducted to determine the light, temperature, and moisture con· ditions under cover crop residue. Hairy vetch (Yicia vil/osa Roth) and rye (Seca/e cerea/e L.) were desiccated with a contact herbicide and residue rates ranging from one-fourth to four times the natural residue biomass were established in experiments at Beltsville, MD and Ithaca, NY. Photosynthetic photon flux density (PPFD) was determined above and below residue at approximately monthly intervals after initiation of the experiment. Transmittance of PPFD through residue declined according to an exponential decay function of residue biomass. Trans· mittance was similar through hairy vetch and rye residue initially, but as the experiment progressed, transmittance through hairy vetch residue was greater than that through rye because of faster decom· position of hairy vetch residue. Spectral analysis from 400 to 1100 nm showed a slight increase in transmittance as wavelength increased resulting in a slight lowering of the red (660 nm) to far-red (730 nm) ratio relative to that of unobstructed sunlight. Soil maximum tem· perature and daily soil temperature amplitude were reduced by cover crop residue. Residue prevented the decline of soil water content dur· ing droughty periods. Results indicated that reductions in light transmittance and daily soil temperature amplitude by cover crop residue were sufficient to reduce emergence of weeds but that maintenance of soil moisture could increase weed emergence.

Effect of cowpea (Vigna unguiculata) intercropping on weed biomass and maize (Zea mays) yield

“…Many Other species, mostly Anchusa italica, Sonchus oleraceus, Glycyrrhiza aspera, Xanthium strumarium, Convolvulus arvensis. studies have reported lower dry weights of weeds in systems that use cover crops because covering the inter-row spaces suppresses weed emergence (Teasdale & Mohler 1993). In the present study, weed infestation levels generally decreased as the densities of both the cover crop and maize were increased (Tables 2 and 3).…”

Manejo de Conyza bonariensis resistente ao herbicida glyphosate

“…Essa supressão ocorre durante a fase de desenvolvimento vegetativo das plantas envolvidas, e as interações são principalmente pela competição pelos recursos do ambiente e pela liberação de substâncias alelopáticas que afetam o crescimento das plantas daninhas (Teasdale & Mohler, 1993).…”

Efeitos de resíduos da parte aérea de sorgo, milho e aveia na emergência e no desenvolvimento de plântulas de leiteiro (Euphorbia heterophylla) resistentes a inibidores da ALS

“…O milho também apresenta potencial de redução de emergência de plantas daninhas, principalmente gramíneas; para cada tonelada de palha houve redução de 6,4 e 4,2% da emergência de plantas daninhas, respectivamente, aos 26 e 41 dias após a semeadura de milho (Oliveira et al, 2001) Os efeitos da palhada sobre as plantas daninhas provêm de efeitos físicos ou alelopáticos, sendo difícil diferenciar um do outro em campo, já que ambos ocorrem de forma simultânea (Maciel et al, 2003). Os efeitos físicos da palha se devem principalmente ao sombreamento do solo, à barreira física para a emergência da plântula da espécie daninha e à manutenção de temperaturas do solo mais baixas, em relação ao solo descoberto (Aase et al, 1991;Teasdale & Mohler, 1993;Vidal, 1995).…”