Abstract.A pot experiment was performed to study the effect of EDTA (0, 1.5, 5.0 mmol/kg) on the cadmium (Cd) accumulation ability of Solanum nigrum L. grown in different Cd-contaminated soils (0,5,10,25, 50, 100 and 200 mg/kg). Meanwhile, soil Cd mobility was evaluated. Results showed that there were significant interactions between Cd and EDTA. Low EDTA dosage (1.5 mmol/kg) significantly alleviated Cd stress to S. nigrum L., although EDTA inhibited the growth of S. nigrum L. grown in non-contaminated soil. High EDTA dosage (5 mmol/kg) could deteriorate Cd stress to S. nigrum L. EDTA could significantly increase the mobility of soil Cd and the Cd content in plant. This research indicated that low EDTA dosage (1.5 mmol/kg) was efficient in assisting remediation of Cd contaminated soil by S. nigrum L. and could lessen second pollution.

Tomato was cultured in an organic substrate with two parts vermiculite and one part sheep manure. The effects of different chemical fertilizer application doses on N, P and K absorption and utilization of tomato were investigated under solar greenhouse conditions. Based on the results, N, P and K absorption and yield of tomato were enhanced by proper fertilizer application. The amount of N, P and K absorbed increased with the increasing chemical fertilizer dose. Also the utilization rate of N and K in organic substrate decreased with increasing fertilizer dose. However, the utilization rate of P increased with increasing of fertilizer dose. Furthermore, transformation of slow-releasing nutrients to available nutrient improved by proper fertilizer application. Under the organic cultivation, producing 1 000 kg tomato required 2.540 kg N, 0.751 kg P, 4.347 kg K. The calculation method of optimal chemical fertilizer dose under organic substrate culture was advanced in the study. The calculation formula was: chemical fertilizer dose = (1.5 times fertilizer dose needed for target yield − available nutrient content in organic substrate)/chemical fertilizer nutrient uptake ratio.