Abstract
The effects of foliar and soil applied phosphite on grain yield in common bean (Phaseolus vulgaris L.) grown in a weathered soil under low and adequate phosphate availability were evaluated. In the first experiment, treatments were composed of a 2 x 7 + 2 factorial scheme, with 2 soil P levels supplied as phosphate (40 e 200 mg P dm-3 soil), 7 soil P levels supplied as phosphite (0-100 mg P dm-3 soil), and 2 additional treatments (without P supply in soil, and all P supplied as phosphite). In the second experiment, treatments were composed of a 2 x 3 x 2 factorial scheme, with 2 soil phosphate levels (40 e 200 mg P dm-3 soil), combined with 3 nutrient sources applied via foliar sprays (potassium phosphite, potassium phosphate, and potassium chloride as a control), and 2 foliar application numbers (single and two application). Additional treatments showed that phosphite is not P source for common bean nutrition. Phosphite supply in soil increased the P content in shoot (at full physiological maturity stage) and grains, but at the same time considerably decreased grain yield, regardless of the soil phosphate availability. Foliar sprays of phosphite decreased grain yield in plants grown under low soil phosphate availability, but no effect was observed in plants grown under adequate soil phosphate availability. In general, foliar sprays of phosphate did not satisfactorily improve grain yield of the common bean plants grown under low soil phosphate availability.
Highlights
Subtropical and tropical regions of the word often exhibit highly weathered soils (e.g. Typic Haplustox) that are characterized by low natural fertility, especially by phosphorus (P) deprivation to plant nutrition
The literature shows that phosphite anion does not replace phosphate anion in P nutrition of the plants (THAO; YAMAKAWA, 2009), and still some works indicated that phosphite supply may cause growth depression in phosphate-deficient plants (SCHROETTER et al, 2006; THAO et al, 2008; THAO et al, 2009; ÁVILA et al, 2011; ZAMBROSI et al, 2011)
The literature shows that some previous studies found harmful effects of phosphite anion on plants grown under low phosphate availability, but no harmful effects have been reported when this anion was applied in plants grown under adequate phosphate availability (TICCONO et al, 2001; VARADARAJAN et al, 2002; LEE et al, 2005; SCHROETTER et al, 2006; DEVAIAH et al, 2007; THAO et al, 2008; MOOR et al, 2009; THAO et al, 2009; ÁVILA et al, 2011)
Summary
Subtropical and tropical regions of the word often exhibit highly weathered soils (e.g. Typic Haplustox) that are characterized by low natural fertility, especially by phosphorus (P) deprivation to plant nutrition. Phosphite salts are marketed as fertilizer because they contain a cation that may be plant nutrient, such as K+, NH +, Ca2+, Mg2+, Cu2+ or Zn2+, and often phosphite is recommended as additional source of P for plant nutrition (ÁVILA et al, 2012a). It was reported that supply of phosphite improved avocado yield (LOAVATT, 1990a), and restored normal growth in phosphate-deficient citrus (LOVATT, 1990b). The literature shows that phosphite anion does not replace phosphate anion in P nutrition of the plants (THAO; YAMAKAWA, 2009), and still some works indicated that phosphite supply may cause growth depression in phosphate-deficient plants (SCHROETTER et al, 2006; THAO et al, 2008; THAO et al, 2009; ÁVILA et al, 2011; ZAMBROSI et al, 2011). Most of the studies that evaluated the effects of phosphite anion on plant P nutrition were related to Arabidopsis, vegetables, seedlings, and some citrus and cereals; but there is still little knowledge about effects of phosphite on leguminous grain yield
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