Nutrient Best Management Practices for Wheat
Fertilization practices for intensive wheat production in Southern Latin America
Fernando O. Garcia
IPNI Latin America – Southern Cone program
This paper summarizes the main best management practices for fertilizer use (FBMP) in wheat in southern Latin America with an emphasis on the Pampas region of Argentina. More information on wheat FBMPs in the region are available in the reviews of Alvarez (2005), Garcia and Berardo (2005), Garcia and Daverede (2007), and Bianchini et al. (2008). Information on nitrogen management in southern Brazil is available at Amado et al. (2008).
Wheat production in the Southern Latin America region - Description of the region
Wheat production in the Southern Cone countries (Argentina, Bolivia, Chile, Paraguay and Uruguay) and Brazil is shown in Table 1. Argentina is the largest producer in the region with 67% of the total area planted to wheat, and 74% of the total wheat production. The highest yields are achieved in the southern countries (Chile, Uruguay, and Argentina), mainly because of better climatic conditions than in the northern countries of the region (Bolivia and Paraguay).
Table 1. Area, production and average yield of wheat at the Southern Cone countries and Brazil.
The Pampas region, located at the east-central plains of Argentina, is the main grain producing area of the country, and includes approximately 90% of the wheat area (Fig. 1). Climate is temperate sub-humid with average annual temperature varying from 14 to 18 ºC, and average annual precipitation increasing from the Southwest (300 mm) to the Northeast (1100 mm).
Year and Source
Mollisols constitute the dominant soils. The humid and semiarid subregions are characterized by Udolls and Ustolls, respectively, with minor occurrence of Aquolls in flat areas (Moscatelli and Pazos, 2000).
In general, soils of the Pampas are deficient in nitrogen (N) and phosphorus (P), but well provided with potassium (K), calcium (Ca), and magnesium (Mg) under native conditions. In recent years, sulfur (S) responses have been observed in several crops, mainly in areas under intensive cropping (high grain yields and longer periods under row crops agriculture).
Crop production in Argentina, Uruguay, Paraguay, and south of Brazil is mainly under no-tillage systems. Estimations indicated that more than 65% of the cropping area is under NT in Argentina (AAPRESID, 2007).
The area of wheat production in Chile is located towards the south of the country, on mollisolls, ultisolls, and inceptisolls of volcanic origin. Climate is of mediterranean type, with most of the precipitation concentrated in fall-winter-spring.
Fig. 1. Location of the main provinces that include the Pampas region of Argentina.
Fertilizer consumption in five countries of the Southern Cone of Latin America is over 2.5 million metric tons N+P2O5+K2O (Table 1). The N:P2O5:K2O ratio is of 6:5.8:1. Argentina is the leading consumer of this group with 59% of the total fertilizer in the region, followed by Chile with 21%, Paraguay with 12%, Uruguay with 7%, and Bolivia with 1%.
In Argentina, field crops (wheat, corn, soybean, and sunflower) explain 75% of the total nutrient fertilizer consumption (Melgar, 2005). Current estimations indicate that 95%, 85%, and 2% of the wheat area receives N, P, and K fertilization, respectively, at average rates of 49 kg N/ha, 30 kg P2O5/ha, and 2 kg K2O/ha.
In Argentina and Uruguay, N sources in wheat are dry and liquid fertilizers, mainly urea and UAN. Ammonium nitrate, calcareous ammonium nitrate (CAN), and ammonium sulfate are also used. At the other countries, urea is the main N source, but ammonium nitrate, calcareous ammonium nitrate, ammonium sulfate, and other nitric sources would be used.
Among P fertilizers, di-ammonium phosphate (DAP), mono-ammonium phosphate (MAP), triple superphosphate (TSP) and single superphosphate (SSP) are the most common sources. In the last years, bulk blending has become a common practice at the Pampas. NP fertilizers and blends are commonly applied at planting, and N fertilization could be carried out pre-plant, at planting or top-dressed at tillering.
Sulfur is applied as calcium sulfate (gypsum), single superphosphate, UAN-ATS liquid solution, or ammonium sulfate among other alternatives. Applications of S are done in blends at planting, broadcasting at pre-plant, or topdressing.
Most of the wheat fertilization in the Pampas is done considering that the wheat crop would mostly be followed by a double crop soybean, and nutrient needs would be supplied for both crops at wheat fertilization time.
Table 1. Apparent nutrient consumption in countries of the Southern Cone of Latin America, between 2003 and 2006. Source: Compilation of IPNI Southern Cone from several local sources.
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Best management practices for fertilizer use (FBMP) in wheat
FBMPs can be aptly described as the selection of the right source for application at the right rate, time, and place (Roberts, 2007). Fertilizer source, rate, timing and placement are interdependent, and are also interlinked with the set of best agronomic management practices applied in the cropping system (Bruuselma et al., 2008). This section summarizes the main FBMPs for N, P, and S of wheat at Argentina and Uruguay.
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