Fatores de variação na caracterização da fertilidade do solo visando adubação: estudo de caso na região sul de Goiás
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Data
2008-07-28
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Universidade Federal de Goiás
Resumo
The next decades will be marked by the increase of the demand of foods and
consumption of chemical fertilizers, mainly in the soils of low fertility of the Brazilian
savannah. The precision agriculture (PA) involves soil sample tests and decisions in input
application rates from computerized and automated machines. The soil fertility is fundamental
for recommendation, and the soil sample tests are used as basic information. The
study evaluated the variation sources in the process of soil samplimg, soil sample tests and
soil fertility maps using kriging. The study considered the difference of two sampling
methods in the vertical distribution of the nutrients at from 0 cm to 10 cm and 10 cm to 20
cm, it tested the number of soil samples necessary to make composed sample, it evaluated
the effect of different instruments to collect soil sample tests and showed the variation
found when sending the same sample for six differents laboratories. The field experiment
was installed at 17o 46'54”S, 49o 28 ' 20”W in two different soils, a oxissol very loamy
and a oxissol loamy. The field has 494,97 meters in length and 777,81 m of width and useful
area 38,5 hectares, subdivided in 77 square cells with 70,71 m of a squared grid. In the
center of each grid cell trenches of 50 cm of depth were open with aid of a mattock, in
which the samples were collected in two depths, 00 to 20 cm and 20 to 40 cm, in all the 77
points of the grid. The standard method was the standard trench (STT). In eight points raffled
in the grid, two samples were collected in the layers from 0 cm to 10 cm and 10 cm to
20 cm, to compare the detection capacity of recognize soil fetility surface concentration. In
other eight raffled points were open more eight trenches, in a radius of ten meters from
STT, in which samples were collected and mixed in a composed sample that was compared
with the simple sample from STT. In more ten other points raffled in the grid the instruments
used to collect samples were tested. The following instruments were tested: Big
Dutch Auger (BDA); Small Dutch Auger (SDA); Thread Auger (THA); Probe Auger
(PRA); Standard Trench (STT). In more three raffled points from the grid bigger samples
were collected for sending the same sample for five different laboratories. Besides that the
temporary variation of two laboratories was compared from Feb/2005 to Jun/2008. The
results of all STT were analyzed by geoestatiscs programs and fertility maps were made
from the calculation of the values of the nugget effect, sill and range of the samples. The
area was was planted with soy, Glyvine max (L.), on 24/11/2006 and the crop was accomplished
in 21/03/2007 in the same points of STT, where samples of the soy plants were
taken for determination of the productivity of the area. The productivity presented pronounced
regional effect, accompanying indexes integrators of the variations as the organic
matter, the clay and pedologic components, and those components seem to be important in
the definition of the income of the cultures and be probably the main factors for spatialy
related to the productivity. The elements in an isolated way didn't show similar structure
variation of the productivity, with variation in shorter distances revealing the need of an
individualized site treatment of the elements, combinin sampling strategies with
interpolation according to the behavior of the element of interest. Using PA concepts to
collect soil samples to generate fertilty maps and applications maps with variable rates, a
grid in the dimensions of the rehearsal should be made being respected the global tendency
observed linked to the soil type, organic matter and clay, instead of that the average of all
results it would avoid the high expenses with analyses. The concentration of nutritious
available in the layer 0 cm to 10 cm it was not detected by the sampling in the layer 0 cm
to 20 cm. The collection of simple samples for composition a composed sample is unnecessary
procedure and showed no increase of precision in collection method. The instruments
used in soil sample collections can cause variations significant and significant in
cost of inputs, being factor important in variation process of diagnosis of soil fertility. The
choice of the laboratory is what more contributed to the total variations found in the study
of all other sources studied variations.
Descrição
Citação
FRANCO, Alexandre Puglisi Barbosa. Fatores de variação na caracterização da fertilidade do solo visando adubação: estudo de caso na região sul de Goiás. 2008. 91 f. Dissertação (Mestrado em Agronomia) - Universidade Federal de Goiás, Goiânia, 2008.