sistemas de culturas em plantio direto adaptados à pequena - UFSM

Lower rates of water infiltration in soil were observed over all time periods (5, 10, 15,
20, 30, 60, 90 and 120 min) studied, in the treatments SDES and CNA, while the
others stay constantly above these and similar. No-tillage with the use of cover crops,
after a long period of use, was efficient in maintaining physical attributes, such as
density and porosity of soil conditions favorable to plant growth, while other attributes
that improved, as the rate of water infiltration, compared with its initial condition of
native pastures. Regarding the production of corn, no-till system using green manure
in summer and winter, after a long period, provided higher yields than systems that
use fallow. The soil cultivation from a native condition determined losses in their
organic carbon content, but this can be recovered with the use of no-tillage system
with a high input of plant residues rich in carbon and nitrogen. Maintenance of the
surface soil exposed to erosion for a long period, caused significant losses in its
carbon content and total nitrogen. No-tillage with the use of summer green manures
(velvet bean) and winter (rye + vetch), promoted increases in the organic carbon
stock in the soil layer of 0.0 – 0.05 m in relation to their initial stock. However, the
layer from 0.0 to 0.20 m depth, none crop system has reached the rated values found
in the reference treatment, in this case, the native grasses. The results for soil and
water conservation were amazing. The maintenance of soil surface exposed rain
erosive action for a long period, led to the progressive loss of a soil layer of about 1
cm per year, equivalent to approximately 150 t ha -1 of soil. No-tillage had, in some
years, water losses smaller than those found under native pasture. Compared with
the losses sustained in soil continuously discovered, the reduction of soil loss by notillage
system reached 99.9%. No-tillage was more effective in reducing soil loss than
the loss of water in crop systems. The wettest and most erosive rains occurred in the
months from October to March, coinciding with the period for the development and
the grain harvest of summer crops, for the conditions of Santa Maria, RS.
Key words: no-tillage, crop rotation, green manure, soil conservation, soil quality