.Upland rice (Oryza sativa L.) cultivation has been increasing in importance in Asia while water availability
for irrigation has been decreasing because of rapid growth in industry and urban centers. Therefore, the
development of technologies that increase upland rice yields under aerobic conditions, thereby saving
water, would be an effective strategy to avoid a decrease in global rice grain production. The use of
the no-tillage system (NTS) and cover crops that maintain soil moisture would prove advantageous in
the move toward sustainable agriculture. However, upland rice develops better in plowed soil, and it
has been reported that this crop does not perform well under the NTS. Therefore, the aim of this study
was to investigate the effect of cover crops on upland rice grain yield and yield components sowed in
a NTS. A field experiment was conducted during two growing seasons (2008–2009 and 2009–2010),
and treatments consisted of growing rice under five cover crops in a NTS and two control treatments
under the conventional tillage system (plowing once and disking twice). Treatments were carried out in
a randomized block design with three replications. Our findings are as follows: On average, Brachiaria
brizantha (12.32 Mg ha−1), Brachiaria ruziziensis (11.08 Mg ha−1) and Panicum maximum (11.62 Mg ha−1)
had outstanding biomass production; however, these grasses provided the worst upland rice yields (2.30,
2.04, and 2.67 Mg ha−1, respectively) and are not recommended as cover crops before upland rice. Millet
and fallow exhibited the fastest straw degradation (half-lives of 52 and 54 days, respectively), and millet
exhibited the fastest nitrogen release (N half-life of 28 days). The use of a NTS was promising when millet
was used as a cover crop; this allowed the highest upland rice yield (3.94 Mg ha−1) and did not statistically
differ from plowed fallow (3.52 Mg ha−1).