The potential mechanism of long-term conservation tillage effects on maize yield in the black soil of Northeast China

The severe soil deterioration and the accompanying decline in maize yield are the main factors jeopardizing the sustainability of agricultural production in the black soil region of Northeast China. Conservation tillage practices have been proposed as new practices to enhance soil fertility and to produce food from a dwindling land resource in this region, but wide adoption of these practices can occur only when the practices demonstrate a steady increase in agricultural production. To compare the effects of tillage on corn yield, the structural equation modeling (SEM) was used in analyzing the relationships between maize growth/yield and soil properties (physical and chemical characteristics) based on a long-term (12 years) tillage study that included no tillage (NT), ridge tillage (RT) and conventional tillage (CT) practices. Compared with CT, NT and RT had higher maize grain yield, soil carbon/nitrogen ratio and soil moisture, and lower soil temperature and seedling emergence rate. The advantages of NT and RT in maize yield were primarily ascribed to the favorable soil nutrients and soil water content, which could increase plant size at the later growing season and ultimately yield more maize grain. The lower soil temperature and subsequently lower emergence rates in NT and RT at early stages (sowing to emergence) of maize growth did not exert negative effects on maize yield. These adverse effects of low soil temperature and low emergence rates could be offset by postponing sowing date without compromising the maize yield. Our study indicated that both NT and RT practices could offer a potentially significant improvement over the current conventional tillage practice in the black soil region of Northeast China.