Agriculture Reference
In-Depth Information
7000
BRSGO Guará
BRS Biguá
CNAi 8886
BRS Jaburu
6000
5000
CNAi 8569
4000
3000
2000
R
2
= 0.92**
R
2
= 0.93**
R
2
= 0.83**
R
2
= 0.88**
R
2
= 0.82**
BRSGO Guará (Y) = 2797.53 + 20.30X
BRS Biguá (Y) = 1814.42 + 19.83X
CNAi 8886 (Y) = 2430.88 + 32.92X - 0.0849X
2
BRS Jaburu (Y) = 1816.19 + 18.21X
CNAi 8569 (Y) = 2590.43 + 24.29X - 0.0631X
2
1000
0
50
100 150
Nitrogen application rate (kg ha
-1
)
200
FIGURE 1.1
Response of five lowland rice genotypes to N fertilization.
main reasons for N deficiency in crop plants are its uptake in large amount compared to other
essential plant nutrients. The uptake of N by most of the annual crops is the highest possible. It
is sometimes equal to or slightly less than potassium by some crops such as rice (Fageria et al.,
2011a). The decrease in organic matter and the loss of the top soil layer by wind and water erosion
are other reasons for N deficiency in crop plants. Furthermore, the dynamic nature of N and its
propensity for loss from soil-plant systems creates a unique and challenging environment for its
efficient management (Fageria and Baligar, 2005). Agricultural productivity gains since the 1950s
resulted in the development of farming systems that rely heavily on external inputs of energy and
chemicals to replace the management and on-farm resources (Oberle, 1994; Porter et al., 2003).
10,000
CNAi 8569
8000
BRS Fronteira
BRS Biguá
6000
4000
R
2
= 0.7709**
CNAi 8569 (Y) = 3356.8340 + 20.8083X
2000
R
2
= 0.7465**
BRS Fronteira (Y) = 3726.6670 + 28.7550X
R
2
= 0.6496**
BRS Biguá (Y) = 2174.000 + 18.6666X
0
50
100 150
Nitrogen application rate (kg N ha
-1
)
200
FIGURE 1.2
Relationship between N and shoot dry weight of three lowland rice genotypes.
