Straw removal and phosphorus fertilization modify plant-available and amorphous soil Si in long-term field trials
摘要
Many plants, especially grasses, contain high concentrations of silicon (Si), which accumulates mainly in the straw as phytolith (SiO2) bodies. Straw harvest exports silicon from arable fields, leading to soil Si depletion over prolonged periods. In addition, phosphate and silicic acid (H4SiO4) compete for sorption sites on mineral soil surfaces. Phosphorus (P) mobilization upon Si fertilization has been reported on several occasions. The opposite effect, i.e. potential increases in soluble Si due to P fertilization has not been studied so far. The aim of this study was to investigate the effect of decades of straw removal in combination with differential P fertilization rates on Si concentrations in soil and plants. Therefore, we analyzed two long-term field trials conducted by the Austrian Agency for Health and Food Safety (AGES) with suitable straw management and P fertilization treatments for effects on soil Si availability and Si uptake by triticale. Our results show that 42 years of straw removal led to a measurable depletion of soluble soil Si at one experimental site, which was reflected in lower plant Si concentrations. At the second site, only slight, but significant effects on plant Si concentrations in early biomass were observed. Moreover, very high P fertilization rates increase soil Si solubility, but not the realistic fertilization rate of 33 kg ha−1 a−1. While it is unlikely that realistic P fertilization rates substantially impact soil Si levels in the agronomical practice, the effect of straw removal will depend on straw export duration and frequency.