The Impact of Fallowing and Green Manuring on Soil Conditions and the Growth of Sugarcane

Abstract

There are currently concerns within some sugar industries that long-term monoculture has led to soil degradation and consequent yield decline. An investigation was conducted in Swaziland to assess the effects of fallowing and green manuring practices, over a seven-month period, on sugarcane yields and the physical properties of a poorly draining clay soil. In the subsequent first sugarcane crop after planting, yields were improved from 129 t ha −1 under continuous sugarcane to 141-144 t ha −1 after fallowing and green manuring, but there were no significant responses in the first and second ratoon crops. Also, in the first crop after planting, root length index increased from 3.5 km m −2 under continuous sugarcane to 5.2-6.8 km m −2 after fallowing, and improved rooting was still evident in the first ratoon crop where there had been soil drying during the fallow period. Soil bulk density, total porosity and water-holding capacity were not affected by the fallowing practices. However, air-filled porosity increased from 11 % under continuous sugarcane to 16 % after fallowing, and steady state ponded infiltration rates were increased from 0.61 mm h −1 to 1.34 mm h −1 , but these improvements were no longer evident after a year back under sugarcane. Levels of soil organic matter were reduced in all cases, probably as a result of the tillage operations involved. In the plant crop, root length was well correlated with air-filled porosity, indicating the importance of improving belowground air supply for crop production on poorly draining clay soils.

Produção de matéria seca e controle de plantas daninhas por leguminosas consorciadas com cana-de-açúcar em cultivo orgânico

“…O potencial das leguminosas no controle cultural de espécies invasoras é descrito na literatura (Fernandes et al, 1999;Severino & Christoffoleti, 2001;Erasmo et al, 2004;Monquero et al, 2009). Na cadeia produtiva de cana-de-açúcar, essa prática é largamente utilizada tanto em sistema orgânico como em convencional, na ocasião da reforma do canavial e antes do plantio da cana de ano e meio, o que proporciona, além da redução da incidência de plantas daninhas, incrementos na produtividade da cultura comercial e melhoria das características físicas, químicas e biológicas do solo (Nixon & Simmonds, 2004).…”

Growth of Root System and the Patterns of Soil Moisture Utilization in Sugarcane under Rain-fed and Irrigated Conditions in Sri Lanka

“…Therefore, it is argued that an extensive root system is useful only as a survival mechanism rather than to prevent significant drought-induced yield reductions (De Costa 2001). Similar situations exist in the growth of sugarcane (Gascho and Shih 1983;Evensen et al 1997;Nixon and Simmonds 2004) and maize (Kang et al 2002) roots under different water regimes. However, significant genotypic variations in the matured sugarcane root systems are found (Evans 1935), and rooting depth and the drought resistance is based on the inherent genetic makeup of the variety (Stevanson and McIntosh 1935).…”

“…It indicates that the bulk of the roots of sugarcane is in the shallow layers of soil. Nixon and Simmonds (2004) also showed that, in the plant crop, 39-45% of roots to 60 cm depth occurred within the top 15 cm, and 65-74% within the top 30 cm of soil.…”

Effect of soybean (Glycine max) as a breakcrop on the cane and sugar yield of sugarcane

“…A seeding rate of 8 tonnes per hectare (Clowes and Breakwell, 1998;Nixon and Simmonds, 2003) was used. Straight cane knives were dipped in a disinfectant called Jeyes fluid to prevent ratoon stunting disease (RSD).…”

“…The increase in total biomass helps much to increase sugar and cane yield (Nixon and Simmonds, 2003;Shoko and Tagwira, 2005). Biomass can be increased through increased interception of solar radiation (Inman-Bamber, 2002).…”