Effects of soil types and fertility management practices on soil silicon availability and banana silicon uptake

Although silicon (Si) is one of soil abundant constituents and one of the key elements enhancing plant disease resistance, banana uptake of Si is limited by soil Si availability. It remains unclear what factors regulates soil Si availability and whether banana Si uptake increases with increasing soil Si availability in home garden soils. To test whether soil Si availability and banana leaf SiO2 contents are affected by soil types or fertility management practices, we measured (1) banana leaf SiO2 contents along the gradient of livestock inputs in Andisols of Tanzania and (2) water extractable Si, phosphate-buffer extractable Si, and banana leaf SiO2 in the home garden soils with different degree of volcanic ash admixing and with/without leguminous trees in Indonesia (East Java and East Kalimantan). Livestock dung application increased banana leaf SiO2 contents in the Tanzanian home gardens. Water extractable Si increased with increasing soil pH, but soil phosphate-buffer extractable Si and banana leaf SiO2 contents were strongly regulated by oxalate-extractable Si and andic properties in the Indonesian home gardens. Effects of companion trees (agroforestry) increased banana leaf SiO2 only in two of three Andisols (Java). These results suggest that banana leaf SiO2 contents could be primarily regulated by admixing degree of volcanic parent materials rich in weatherable minerals, but that banana leaf SiO2 contents could also be increased by inputs of livestock dung rich in Si (Tanzania) and agroforestry (Indoensia).