Soil fertility and crop fertilization management for high yields in the pampean region 1 Fernando O. García INPOFOS Cono Sur Potash and Phosphate Institute - Potash and Phosphate Institute of Canada Av. Santa Fe 910 – (B1641ABO) Acassuso, Buenos Aires, Argentina
[email protected]
Soil fertility and crop fertilization management for high yields in the pampean region Abstract Grain production has sharply increased in the last decade in Argentina, approximately 74% in the period 1991-2000, mainly because of increases in planted area but not in average grain yields. Also, average grain yields of several areas of the Pampas, the main grain production area of the country, are below potential yields. Soil fertility and crop fertilization management could improve grain yields. Nitrogen (N), phosphorus (P), and sulfur (S) are the main deficient nutrients in the pampean region. Deficiencies and responses to other nutrients have been observed for specific crops and areas, i.e. chloride response in wheat in the western pampas. Recent and current research and experimentation show the contribution of N, P, and S management on increasing yields of field crops such as soybean, wheat, and corn. Current ratios of grain/fertilizer prices (November 2002) are favorable to develop fertilization practices according to crop requirements and soil fertility conditions.
Grain production in Argentina, mainly at the Pampean Region, has sharply increased in the last decade (Fig. 1). For soybeans, this increase was mainly due to area expansion rather than yield increases (Table 1). Production increases in wheat and corn showed a greater equilibrium between area expansion and yield increases. Sunflower moderated its decrease in sown area since 1998 with higher national average yields. Research has demonstrated that average yields in different ecological areas are below the potential yields that may be reached under normal soil and climate conditions. Figure 2 shows the gap estimated between average and potential yields for three situations in the Pampas: wheat in the South, and corn and full season soybeans in the North. In all cases, it has been considered the use of technologies available to advanced farmers but no irrigation. The low increase in national average grain yields in the last decade and the yield gap between average and potential yields, indicates that the knowledge and adoption of adequate crop and soil management practices are required in order to improve farmer´s profits and grain production in the Pampas.
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Presented at the 4ª Conference “Fertilizantes Cono Sur” organized by British Sulphur Pub. – Porto Alegre, Brasil – 18-20 November 2002.
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Nutrients generally deficient in the Pampas soils are nitrogen (N), phosphorus (P) and, in the last years, sulfur (S). Deficiencies and responses to other nutrients such as magnesium (Mg), potassium (K) and micronutrients have been reported for specific crops and areas. As it was shown for grain production, fertilizer consumption has sharply increased in Argentina in the 1991-2000 decade (Fig. 3). This increase correlates with grain production (Fig. 4), but it is not the only cause of it. The massive adoption of no-tillage, the release of new high yielding hybrids and varieties, and the adequate use of herbicides, insecticides, and fungicides have been decisive factors to achieve national harvests over 60 million t. Despite of the increase in fertilizer consumption since 1991, nutrient balance (nutrient application vs. nutrient removal) is still negative. In the last years, the removal:use ratio for N, P, and K in the main grain crops has been of 3.3-5, 2-2.5, and +100, respectively (Fig. 5). These negative balances has resulted in a significant deterioration of the fertility status of soils. Soil fertility and crop fertilization management will contribute to narrow the yield gap between present and potential grain yields and, then, improve average yields in the Pampas. A good example are the data shown in Figure 6. Balanced NPS fertilization allowed to get significant increases in grain yield in both cases, low (corn 2001) and medium (corn 2000) soil fertility conditions. Similar yields have been obtained under both soil fertility conditions with balanced NPS fertilization (NPS removal treatment). Another point of interest is the difference observed between NPS treatments, the NPS treatment based on nutrient removal yielded approximately 1800 kg/ha more than the NPS treatment based on present recommendations. This indicates that current fertilization recommendations are below the optimum for present grain yields. A summary of recent advances on crop fertilization management in the Pampas is presented in the next sections. Corn In the northern Pampas, a pre-plant soil nitrate test (soil nitrate-N availability at 0-60 cm depth + fertilizer N applied at planting) is used to recommend N fertilization. A level of 100-150 kg/ha nitrate-N is suggested to reach grain yields of 9000-10000 kg/ha. Field experiments conducted by AAPRESID and Profertil in the 2001/02 growing season demonstrated that grain yields of 12000 kg/ha or more may be obtained with soil nitrate-N availability of 170 kg/ha nitrate-N (Fig. 7) (Bianchini et al., 2002). On P management, a relationship between P use efficiency and soil Bray P has been established indicating that, with the current ratios of grain/fertilizer prices, profitable responses to P fertilization could be obtained with soil Bray P levels of 16-17 ppm or less (Fig. 8). Responses to S fertilization have been determined in sites with high response to N. This is explained because the main soil source for both nutrients is the organic matter. Losses of soil organic matter result in N deficiencies and, later, in S deficiencies. The N*S interaction is clearly demonstrated by results of field trials such as the one shown in Fig. 9 (Capurro et al., 2002). As well as for wheat and soybeans, a S soil test has not been calibrated yet, but current research is studying several methods.
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Wheat On N, recent experiments have shown a significant N*variety interaction (Calviño and Redolatti, 2002). High yielding varieties of French origin are more efficient using N and reaching higher yields than traditional varieties. An aspect under evaluation regarding N in wheat is the use of foliar fertilization in advanced stages of development (anthesis) to improve grain quality (Ricardo Bergh, CEI INTA-MAA Barrow, pers. comm., 2002). Soil Bray P critical levels have been estimated in 14-15 ppm for wheat crops of the northern Pampas with yield goals of 3500 kg/ha (Fig. 10), and in 20-22 ppm for wheat crops of the southern Pampas with yield goals of 6500 kg/ha. Chloride applications, as potash or ammonium chloride, have resulted in significant yield responses in trials carried out at the western Pampas (Díaz Zorita et al., 2002) (Fig. 11). These evaluations continue during the current growing season to determine areas and conditions of potential response to chloride. Soybeans The net of fertilization trials of Project INTA Fertilizar has confirmed a soil Bray P critical level of 12-14 ppm for profitable responses to P fertilization (Echeverría et al., 2002). Figure 12 shows the relationship between soil Bray P and P use efficiency for 47 trials conducted by INTA, Project INTA Fertilizar, and the Faculty of Agronomy (UBA) between 1997 and 2001. Soil Bray P levels of 12 ppm or less present P use efficiencies of 11 kg soybean per kg P or greater, above the current ratio of grain/fertilizer P prices. Soybean has been the crop that shows greater responses to S fertilization, as direct application to full season soybeans or residual applications to double cropped wheat-soybeans. Residual effects of P and S Current research at West Central Buenos Aires (9 de Julio, Buenos Aires) (Ventimiglia et al., 2001), and East Central Santa Fe (B. De Yrigoyen, Santa Fe) (Vivas et al., 2002) have shown significant P and S residual effects in Hapludoll and Argiudoll soils. The low P fixation of Pampas soils was already demonstrated by research conducted between 1988 and 1993 in Argiudoll of Southern Buenos Aires (Berardo et al., 1994). Figure 13 shows P residual effects of different P fertilization treatments in the first three years of the experiment at 9 de Julio (Buenos Aires) with initial soil Bray P of 9 ppm. The net of trials of Project INTA Fertilizar also confirmed the residual effects of P and S fertilization in wheat on the double cropped soybeans (Echeverría et al., 2002). Final comments Most of the increase in grain production during the last decade in Argentina could be attributed to area expansion of the main crops. Average
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grain yields have increased moderately and, in several areas, a significant yield gap (30-40%) between current and potential yields is estimated. Adequate soil fertility and crop fertilization management would contribute to improve national grain yield averages and narrow the yield gap between current and potential levels. Management of N, P, and S should be generally considered, but responses to other nutrients have also been reported for special crops and areas (i.e. chloride in wheat in the Western Pampas). Current ratios of grain/fertilizer prices are favorable for the development of fertilization management plans according to crop needs and soil fertility status. References Berardo A., F. Grattone, R. Rizzalli and F. García. 1994. Residual phosphorus evaluated for soils of Southeast Buenos Aires province. Better Crops International 10 (1):3-5. Potash and Phosphate Institute. Norcross, Georgia, EE.UU. Bianchini A., F. Llambias, M. Ambrogio and S. Lorenzatti. 2002. Nitrógeno para mejores rendimientos. Siembra Directa 13 (62): 20-22. AAPRESID. Rosario, Santa Fe, Argentina. Calviño P. and M. Redolatti. 2002. Diagnóstico de nitrógeno en trigo con variedades de distinto potencial de producción. Actas CD XVIII Congreso Argentino de la Ciencia del Suelo. AACS. Puerto Madryn, Chubut, Argentina. Capurro J., C. Fiorito, M. González and R. Pagani. 2002. Fertilización del cultivo de maíz en Cañada de Gómez (Santa Fe): Resultados del ensayo campaña 2001/02. Informaciones Agronómicas del Cono Sur 15: 8-11. INPOFOS Cono Sur. Acassuso, Buenos Aires, Argentina. Díaz Zorita M., G. Duarte, M. Barraco and M. Fornasero. 2002. Respuesta de cultivos de trigo a la fertilización con cloruros. Actas CD XVIII Congreso Argentino de la Ciencia del Suelo. AACS. Puerto Madryn, Chubut, Argentina. Echeverría H., G. Ferraris, G. Gerster, F. Gutiérrez Boem and F. Salvagiotti (Ex aequo). 2002. Fertilización en soja y trigo - soja: Respuesta a la fertilización en la región pampeana. Resultados de la red de ensayos del proyecto fertilizar – INTA. Campaña 2000/2001 y 2001/2002. Proyecto Fertilizar INTA. EEA INTA Pergamino. Buenos Aires, Argentina. En www.fertilizar.org, rev. 30/10/02. Ventimiglia L., H. Carta, S. Rillo, M. Conti, and F. García. 2001. Phosphorus and potassium fertilization and residual effects in a loam soil in the argentinean Pampas. Agronomy Abstracts. ASA-CSSA-SSSA. Madison, Wisconsin, EE.UU. Vivas H., H. Fontanetto, R. Albrecht, M. Vega and J. Houtian. 2002. Fertilización con P y S en el doble cultivo trigo-soja. Residualidad en soja. Respuesta física y económica. Anuario 2001. pp. 114-118. EEA INTA Rafaela. Santa Fe, Argentina.
Production (thousand t)
5
Corn Wheat
30000 25000
Soybeans Sunflower
20000 15000 10000 5000 0 1990
1992
1994
1996
1998
2000
Figure 1. Evolution of corn, wheat, soybeans, and sunflower production in Argentina. Period 1991-2000. Source: SAGPyA.
Table 1. Annual average rate of growth in production, area, and yield of soybeans, wheat, corn, and sunflower in Argentina for the period 1991-2000. Elaborated form data of SAGPyA. Crop Production Area Yield thousand t thousand ha kg/ha Soybeans 1596 557 43 Wheat 751 211 50 Corn 774 100 110 Sunflower 196 87 19
Grain yield (kg/ha)
12000
Current
10000
+ 42%
Potential
8000 6000
+ 41%
+ 30%
4000 2000 0
Wheat South
Corn North
Soybeans North
Figure 2. Estimation of current and potential grain yields for wheat in the southern Pampas, and corn and full season soybeans in the Northern Pampas
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1800
Nitrogen Phosphates Others
Thousand t
1500 1200 900 600 300 0
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
Figure 3. Evolution of fertilizer consumption in Argentina. Period 1991-2001. Source: Ing. Mario Medana (SENASA-SAGPyA).
Grain production (thousand t)
70000 2000
1997
60000
1999 1998
50000 1996 40000
1991
1994
1995
1993 1992
30000
Production = 17.6 Consumption + 25807 2 R = 0.79
20000 0
500
1000
1500
2000
Apparent fertilizer consumption (thousand t) Figure 4. Relationship between grain production and apparent fertilizer consumption in Argentina for the period 1991-2000. Elaborated from information of SAGPyA and SENASA (Ing. Mario Medana).
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Consumption NPK
Removal NPK
thousand t
1200 900
657
600
280
300
1200 miles ton
Sunflower Soybeans Wheat Corn
1392
900 600 300
340 119
0
0 N
P
N
K
P
3 K
6000
12464
10863 6839
9000
12420
10422
12000 5401
Grain yield (kg/ha)
Figure 5. Removal of N, P and K by grains of soybeans, wheat, corn and sunflower and consumption of N, P and K by the same crops in the 2000/01 growing season in Argentina. For soybeans, it was considered that 50% of the grain N was supplied by N2 fixation. Elaborated from data of SAGPyA, SENASA (Ing. Mario Medana), and INPOFOS.
Testigo NPS diagnosis NPS removal
3000 0 Corn 2001
Corn 2000
Figure 6. Corn yield under different fertilization treatments at two sites of suotheastern Córdoba. Site Corn 2001 was characterized as low soil fertility, Site Corn 2000 was characterized as medium soil fertility. NPS diagnosis is the rate according to current official recommendations, and NPS removal is the rate estimated form grain nutrient concentration and production. Source: V. Gudelj et al. (pers. comm., EEA INTA Marcos Juárez, Córdoba).
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Yield = -0.096 N 2 + 58.9 N + 4905 R 2 = 0.701
Grain yield (kg/ha)
16000 14000 12000 10000 8000 6000
0
50
100
150
200
250
300
350
400
Nitrate-N at planting (0-60 cm)+ fertilizer N (kg/ha)
P use efficiency (kg corn/kg appliedP)
Figure 7. Corn yield as function of N availability at planting (soil nitrate-N 0-60 cm + fertilizer N) in 5 trials in the 2001/02 growing season at Córdoba and Santa Fe. Source: Bianchini et al. (2002).
PUE = 721.3 e -0.221 P Bray R 2 = 0.668
120 100 80 60 40 20 0 0
5
10
15
20
25
Soi Bray P (ppm) Figure 8. P use efficiency in corn as function of soil Bray P in 12 trials of INTA and CREA South of Santa Fe at the Northern Pampas.
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Corn yield (kg/ha)
Without S
With S
13000
Yield = -0.11 N 2 + 47.3 N + 6728 R 2 = 0.966
11000 9000
Yield = -0.15 N 2 + 37.9 N + 6668 R 2 = 0.885
7000 5000
0
30
60
90
120
150
N rate (kg/ha)
P use efficiency (kg wheat/kg applied P)
Figure 9. Corn yield with different rates of N at planting and with or without S fertilization. Cañada de Gómez (Santa Fe), 2001/02. Source: Capurro et al. (2002).
60
-0.2357 Bray P
PUE = 373.53e 2 R = 0.8045
50 40 30 20 10 0 0
5
10
15
20
25
Soil Bray P (ppm) Figure 10. P use efficiency in wheat as function of soil Bray P in 9 trials of INTA, CREA South of Santa Fe and AAPRESID at the Northern Pampas.
Wheat yield (kg/ha)
10
3500
3455
3507
23
46
3374
3096 3000 2500 2000 0
69
Cl rate (kg/ha)
P use efficiency (kg soybeans/kg applied P)
Figure 11. Wheat yield as function of Cl rates. Averages of three experiments at Northwestern Buenos Aires, 2001/02. Source: Díaz Zorita et al. (2002).
40
PUE = -11.05 Ln (Bray P) + 38.9 2
R = 0.454 30 20 10 0 0
10
20
30
40
50
60
-10 Soil Bray P (ppm) Figure 12. P use efficiency in soybeans as function of soil Bray P in 47 trials of INTA, Project INTA Fertilizar, and Faculty of Agronomy (UBA).
2989 3785 4553 4990 5566
9000 6000 3000
1996 2049 2177 2764 2945
12000
Check P 10 P 20 P 40 P 80
10117 10159 10843 11708 11771
Grain yield (kg/ha)
15000
10544 11096 12346 12342 13646
11
0
Corn 1999
Wheat 2000
Soybeans 2000
Corn 2001
Figure 13. Grain yields of corn (1999), wheat (2000), double cropped soybeans (2000) and corn (2001) with different P rates applied at planting of corn in 1999. Inchausti (9 de Julio, Buenos Aires). Source: Luis Ventimiglia et al., UEEA INTA 9 de Julio, (pers. comm.).
