1 INTRODUCTION
The São Paulo State Secretariat for Agriculture and Supply (SAA) is
responsible for the regulation of soil use and conservation, as well as
the combat against soil erosion. Through the Coordination of
Agricultural Defense (CDA), it enforces the Law on Use, Conservation and
Preservation of Agricultural Soil - State Law nº. 6.171/88 - (São Paulo,
State, 1988), with the purpose of monitoring and controlling soil use
and conservation.
This agency has been carrying out this work for 20 years, with very
positive results, with inspections carried out mainly in watersheds.
Approximately 18 million hectares of the surface of the state of São
Paulo is occupied by agriculture, with 330 thousand agricultural
properties. During that period, from 2000 to 2019, 772,000 hectares were
inspected, with 19,846 agricultural properties having been notified and
agroecologically rehabilitated (Vischi Filho et al., 2019).
The CDA Diagnostic methodology uses conservation law as a tool, and
considers the watershed as the ideal work unit for carrying out this
type of activity. The watersheds play an important role in regulating
the water balance, as well as housing agricultural production, and
promoting rainwater storage , which seeps into the soil and is available
to rivers throughout the year (Lal, 1994; Vischi Filho et al., 2018 and
2019).
The lack or deficiency of vegetation cover in crops results in
degradation of the watershed, leading to erosive processes that cause
the silting of the watershed water network and interfering in the
quantity and quality of the water (Rodrigues et al., 2015). The first
principle of soil conservation is soil cover, whether vegetation or
mulch. Agricultural practices such as the use of varieties that provide
larger plant coverage of the soil, reduce the direct impact of raindrops
on the soil surface, hence reducing the loss of soil , water, organic
matter, and nutrients due to hydric erosion (Silva et al., 2005;
Rodrigues et al., 2015; Merten et al., 2016).
The inappropriate use of agricultural soils causes the gradual loss of
its productive capacity, and the contamination of water resources by
sediments resulting from the erosion process (Araujo, et al., 2007;
Lelis & Calijuri, 2010). The last decades have been characterized by
drastic changes in land use and occupation in the region, which Zalidis
et al. (2002) considered one of the main driving forces for
environmental degradation, especially on soil and water. This is a
result of the absence, or flawed implementation, of conservationist
practices in the cultivation areas of agricultural properties, which is
commonly observed in Brazil, mainly in pasture areas (Menezes et al.,
2009). The irrational management of the soils compromises the vegetation
cover, the production and the ecosystems’ balance (Santos et al., 2007).
For each soil and crop, the most fitting strategy is recommended, having
an impact in the reduction of the hydric erosion (Silva et al., 2009).
The second principle of soil conservation is to avoid that the surface
run-off regime goes from laminar to turbulent and, for that, the
construction of an agricultural terracing system is carried out, which
has the function of sectioning the length of the ramp and promoting the
infiltration of soil water. According to Pruski (2006), the more the
soil surface is protected by vegetation cover, against the rain action,
the lower the susceptibility to erosion. Studies by Minella et al.
(2007) to identify the origin of sediments in watersheds concluded that
the areas of crops are the main sources of sediments, and suggested that
programs for the implementation of conservationist management of soil
practices are essential. By adopting adequate management and mitigation
actions to recover the impacted areas, there will be an improvement in
water quality of the watersheds (Araújo et al., 2009). The ultimate
product of soil conservation is its contribution to minimizing floods
during periods of heavy rainfall and increasing water availability in
the annual dry period.
In this work on the inspection of Rio do Peixe watershed, the type of
intervention aimed at transforming conventional and soil-degrading
agriculture into conservationist agriculture, implementing
conservationist technical projects that contemplated this novelty.
Conservation Agriculture is an agricultural system that promotes the
maintenance of permanent soil cover, minimal soil disturbance or
no-tillage, and the diversification of plant species. This increases
biodiversity and natural biological processes below and on the soil
surface, contributing to higher the efficiency in the use of water and
nutrients, and an improvement and sustainability agricultural production
(FAO, 2019).
The use and conservation of the soil at Rio do Peixe watershed was
inspected for a period of 12 years, ending in 2019 in particular
sections I, II and III, located in Vera Cruz, Ocauçu and Marília. This
work aimed to test innovations for diagnosis of agricultural properties;
to locate erosions; and to correct them, with modification in soil
management strategies. The overarching goals was to transform the
degraded agricultural properties at Rio do Peixe watershed into restored
properties, promoting conservationist agriculture, and evaluating the
results through remote sensing and water quality indicators.
2 MATERIALS AND METHODS