Metal elemental composition of maize straw and MSB.

Concentrations	Maize straw	Soil	MSB0	MSB1	MSB2	MSB3
Na (g kg−1)	0.52	0.36	1.03	1.29	1.75	2.15
Mg (g kg−1)	3.48	5.78	2.09	3.30	4.75	5.15
Fe (g kg−1)	0.18	10.46	0.73	1.62	1.99	2.68
Cu (g kg−1)	0.00	0.01	0.00	0.00	0.01	0.01
Zn (g kg−1)	0.15	0.04	0.01	0.03	0.06	0.07
K (g kg−1)	12.17	2.39	12.18	12.47	14.72	15.73
Pb (mg kg−1)	NDa	8.01	NDa	NDa	NDa	NDa
Cd (mg kg−1)	0.20	0.21	0.13	0.15	0.20	0.21

^aNot detected.