Soybean Yield Induced by Winter Crops in No Tillage System in Tropical Region.
Monday, November 2, 2009
Convention Center, Exhibit Hall BC, Second Floor
Jose Cora, Adolfo V. Marcelo, Marcio R. Martins, Carolina Fernandes and Ricardo F. Jorge, Soil Science - Campus of Jaboticabal, Sao Paulo State Univ., Jaboticabal, Brazil
The no-tillage system is
utilized in approximately 30 million hectares in Brazil. However, this system still
needs to be better adapted to tropical regions, with warm and dry winters,
common in the southeast and central-west of Brazil. To achieve this, the choice
of adapted crops to establish the system is of fundamental importance. This
selection should take into consideration, besides economic return, the
maintenance or improvement of chemical and physical properties of the soil
which contribute to improve productive capacity. The purpose of this study was
to evaluate the influence of winter crops on soybean yield in no tillage
system. The field experiment was established in 2002 and conducted for seven
growing seasons (2002-2009) at Jaboticabal, SP, Brazil,
(21°14′S, 48°17′W and altitude of 550 m). Climatologically the
area belongs to tropical/megathermal zone or Köppen's Aw. The mean annual rainfall is 1417 mm, with an
annual distribution peaking in the period of October to March and a relatively
dry season in the period of April to September. The soil of the experimental
area is a RhodicEutrudox.
In the 0–20 cm layer, the mean contents of clay, silt
and sand is 555, 63 and 381 g kg‑1, respectively. The
experiment was conducted using a randomized block design, with tree replication.
The treatments consisted of seven winter
crops, sowed in February-March and repeated every year in the same plots:
maize, sunflower, oilseed radish, pearl millet, pigeon pea, grain
sorghum and sunn hemp. The results showed that the
highest soybean yields were obtained after sunn hemp,
probably, due to the highest soil P contents observed in the sunn hemp plots. And the lowest soybean yield after sorghum
was, probably, due to the allelopathic effect of several
components released by sorghum residues during decomposition negatively
affecting the following crop.