Print version ISSN 1516-8913
Braz. arch. biol. technol. vol.43 no.3 Curitiba 2000
Evaluation of Nutrient Status and Grain Yield of Two Corn Cultivars Under Different Soil Aluminum Levels After Liming
Volnei Pauletti1*, Beatriz Monte Serrat Prevedello2, Amir Pissaia3 and Airton Scopel2
1 Fundação ABC, Cx. Postal 1003, 84.166-990, Castro, Paraná - Brazil; 2 Departamento de Solos-UFPR, Rua dos Funcionários s/n, 80035-050 Curitiba, Paraná - Brazil; 3 Departamento de Fitotecnia e Fitossanitarismo-UFPR, Rua dos Funcionários s/n, 80035-050 Curitiba - Paraná, Brazil
This study was conducted to evaluate the effects of decreasing levels of Al saturation through the addition of lime under field conditions in the nutritional status and grain yield of two corn (Zea mays L.) cultivars: one tolerant and one non-tolerant to Al. The experiment was conducted on Red Yellow Latosol (Oxisol) at the Paraná, Brazil. Control plots received no lime (T0), the treatment T3 received lime to achieve 0% Al saturation and treatments T1 and T2 recieved 33.3% and 66.6%, respectively, of the lime applied to treatment T3. At full bloom stage, representative leaves ("nutritional leaves") were analysed for macro, micronutrients and Al contents, and in treatments T0 and T3 were also analyzed for Al distribution in shoot plants parts (stem, node, internode and leaves). Liming increased concentrations of N, P and Mg and decreased concentrations of Mn and Al in the "nutritional leaves"of both cultivars. The Al distribution in the shoot plant parts showed that its concentration was higher in the leaves than in any other plant part, independent of liming level. Grain yield of the tolerant cultivar was higher, although for both cultivars increase in yield was correlated with decrease in Al saturation.
Key words: Aluminum, acid soil, liming, tolerant, Zea mays, corn
The presence of aluminum at toxic levels in the soil is one of the most important factors limiting agricultural production in tropical and subtropical climates, being a problem in over 50% of the Brazilian soils (Silva, 1976). Toxic Al symptoms are observed mainly in the roots (McLean & Gilbert, 1927), influencing the nutritional status of the plant as a whole. Al decreases levels of Ca, (Malavolta et al., 1989), Mg (Fahl et al.., 1980), P (Ramires &Berengel, 1984), Zn, Mn
(Clark, 1977) and Cu (Cambraia et al.,1983a) in the shoot parts of cultivated plants, thus affecting crop production (Clark, 1977; Cambraia et al., 1983b; Quaggio et al., 1987). The magnitude of the effects vary with species and cultivars, indicating the probable existence of individual mechanisms for Al tolerance as an adaptation to acidic soil conditions.
The objective of the study was to evaluate the effect of different levels of soil Al toxicity on the grain yield and nutritional status of two corn cultivars: one tolerant and one not tolerant to Al.
MATERIALS AND METHODS
The experiment was conducted at the Centro de Estações Experimentais - UFPR - Paraná, Southern Brazil ( 49 o 08 W; 25 o 25 S and 930 m of altitude).The average annual precipitation is 1500 mm with máximum temperature of 24ºC and minimum of 12ºC. The soil was classified as a Red-Yellow Latosol (Oxisol), whose chemical and physical characteristics are shown in Table 1.
The treatments arranged in a randomized complete block design, with four replications, consisted of four liming levels (dolomitic lime) applied to the soil prior to corn sowing. The cultivars used were HS7777 (non-tolerant to Al) and C525 (tolerant to Al) (Furlani & Hanna, 1984 and Furlani, 1993). 12, 90 and 30 kg ha-1 of N, P2O5 and K2O, respectively, were applied at the furrow slice. Supplementary fertilizer (30 kg ha-1 of N and 15 kg ha-1 of K2O) was added the soil 30 days after seed germination and at 60 days, 30 kg ha-1 of N. The liming levels were calculated through the construction of a calibration curve. The control treatment (T0) received no lime, and the highest level of liming (T3) was calculated so that the soil achieved 0% Al saturation (10.5 t MgCaCO3 ha-1). Treatments T1 and T2 received 33.3% and 66.6%, respectively, of the lime applied to T3. Table 2 presents the soil chemical analysis after treatment applications, at sowing and after harvest. The pH was determined by CaCl2 0,01M (1:2,5) method, H+Al by SMP, Ca,Mg and Al by KCl 1N (1:10) with EDTA 0,0125M titulation for Ca and Mg and NaOH 0,025N titulation for Al. K and P were determined by the Mehlich 1 (1:10) method, acording to EMBRAPA (1979).
At full bloom stage the first leaf bellow and opposite to the corn ear (chosen as representative of the plant nutritional status) of 20 random plants in each plot was harvested. A composit sample of the central part of these so called "nutritional leaves" was submitted to a 100 g/dm3 HCl digestion and analyzed for N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, B and Al content. The N was determined by the Kjeldahl digestion method, P and B by colorimetry and the remaining elements by atomic absorption spectrophotometry. Three whole plants in treatments T0 and T3 were also analysed for Al distribution in the stem, node, internode and leaves. At the physiological maturity stage, the plants were harvested and the grain yield was measured.
All data were subjected to analysis of variance to determine treatments and interaction effects. Relationships between liming levels and nutrient content of the "nutritional leaves" , and grain yield were analyzed by means of linear regression. Correlation tests were performed between foliar nutrient content and soil pH and Al saturation.
RESULTS AND DISCUSSION
Different liming levels did not affect significantly the concentrations of K, Ca, Zn, Cu and B in the "nutritional leaves" of both cultivars. The tolerant cultivar had significantly higher levels of all nutrients, except for Ca (Table 3).Onlyconcentration in the tolerant "nutritional leaves" showed a significant correlation with soil pH (r = 0.64) and soil Al saturation (r = -0.64). This indicates a possible relationship between Ca absorption and Al tolerance, as suggested by Foy & Brown (1963) and Foy & Fleming (1978).
Mg levels in the "nutritional leaves" of both cultivars increased with liming (Fig.1). The average Mg content of the tolerant cultivar was higher (Table 3), mainly in treatments with lower Al in the soil (T2 and T3). This is an important result, once this difference among tolerant and non-tolerant cultivars has not been observed in nutrient solution experiments (Ramirez & Barengel, 1984; Cambraia et al., 1983a).
Only N content of the tolerant cultivar which was consistently higher than that of the non-tolerant cultivar (Fig 2), was considered satisfactory for corn growth ( Malavolta et al., 1989). A significant negative correlation was found between Al saturation in the soil and N content in the leaves of the tolerant cultivar (r = -0.78), which seemed to be more efficient in absorbing this element.
The tolerant cultivar also showed higher absorption of P (Fig. 3). Foliar levels of P were significantly correlated with pH (r = 0.86), soil Al saturation (r = -0.80) and corn production ( r = 0.80), which suggest a possible relationship between Al tolerance and P absorption and translocation ability of the cultivar (Ramirez & Berengel,1984).
Addition of lime resulted in higher Fe content only in the tolerant cultivar (Fig. 4). Such a difference between cultivars was not observed by Clark (1977) or Cambraia et al. (1983a), working with nutrient solution.
Levels of Mn decreased with liming for both cultivars (Fig. 5). Foliar Mn was negatively correlated with levels of lime (r=-0,60 in tolerant and r=-076 in non-tolerant) demonstrating the lime effect in decreasing Mn availability for plant uptake (Fassbender,1982; Ritchey et al., 1982,Quaggio, 1989). Clark (1977) and Cambraia et al. (1983 a) observed an inverse behavior in corn cultivars growing in nutrient solution, possibly because of competition between Al and Mn for absorption sites (Alan & Adams, 1979). Significant negative correlations were found between Mn x Ca (r = -0.77) and Mn x Mg (r = -0.73) for the tolerant cultivar, and only between Mn x Mg (r = -0.66) for the non-tolerant cultivar, showing the same compensation effect in cation absorption (Marschner,1986).
Increase in liming decreased Al concentration in the "nutritional leaves" of both cultivars due to the decrease in exchangeable Al in the soil (Fig. 6). The Al distribution in the shoot plant parts (Fig. 7), however, showed that the concentration of the element was higher in the leaves than in any other plant part, independent of the liming and/or Al neutralization in the soil. The concentration in all plant parts, except the nodes of the tolerant cultivar, decreased with the lime.
Grain yield increased in a linear way with the quantity of lime added, with the tolerant cultivar being more responsive to liming and significantly more productive (Fig.8).
Corn yield was negatively correlated with Al saturation in the tolerant (r=-0.65) as well as non-tolerant (r=-0.69) cultivars, indicating reduction of Al saturation in the soil as one of the possible effects of liming in grain yield.
Este estudo teve o objetivo de avaliar o efeito de níveis decrescentes de saturação por Al em função da calagem, em condições de campo, na nutrição e produtividade de grãos de dois cultivares de milho: um tolerante e outro sensível ao Al. O experimento foi conduzido em um Latossolo Vermelho-Amarelo (Oxisol), no estado do Paraná - Brasil. O tratamento T0 não recebeu calagem, o tratamento T3 recebeu calagem para obter 0% de saturação por Al e os tratamentos T1 e T2 receberam 33,3% e 66,6% da quantidade aplicada no T3, respectivamente. No pleno florescimento foram coletadas folhas representativas do estado nutricional ("folhas nutricionais") para análise dos macro e micronutrientes e Al. Nos tratamentos T0 e T3 foi avaliado a distribuição do Al na parte aérea (caule, nó, entre-nó e folhas). A calagem aumentou a concentração de N, P e Mg e diminuiu a de Mn e Al nas "folhas nutricionais" nos dois cultivares. A distribuição do Al na parte aérea mostrou maior concentração nas folhas que nas outras partes da planta, independente da calagem. A produtividade de grãos do cultivar tolerante foi maior, entretanto, para ambos os cultivares, o aumento da produtividade correlacionou-se com o decréscimo da saturação por Al.
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Received: May 17, 1999;
Revised: July 26, 1999;
Accepted: February 02, 2000.
*Author for correspondence