Effect Of Steel Slag Application On Acid Vegetable Soil

Intensive planting and large dose of fertilizing induced the vegetable soil changing acid rapidly. Acidification is the main adverse factor that keep farmland healthy and been sustainably used. So, modifying acid soil became the hot point for vegetable planting. Two group of pot experiments with vegetable farmland soils with eight years of planting vegetables were carried out to investigate the effect of steel slag addition on soil physiochemical characters, vegetable production, nutrient absorption and soil and food safety under soybean-radish-pepper- asparagus lettuce and pepper-lettuce-tomato rotation. These were used to evaluate the rationality and safety of steel slag used as acid soil modifier. The results were as following:The results of two groups of experiments indicates that compared with CK, the soil pH increases with the increasing dose of steel slag, and continuous addition of3.0 g/kg steel slag four times induces the soil pH increasing 2.8. Only sequential addition of more than 2.0 g/kg steel slag four times can increase the soil organic matter obviously with the return of inedible parts to the soil. This means that the effect of steel slag on soil organic matter transformation is of dosage and time dependent. Continuous use of steel slag decreases the soil alkali-hydrolyzable nitrogen even by 29.6%. Continuous addition of more than 2.0 g/kg steel slag increases the soil available P and exchangeable Ca remarkably, and the increasing degree is up to 60%. Continuous addition of more than 1.0 g/kg steel slag increases the soil exchangeable Mg, but the increasing degree is less than 30%.Compared with CK, adding 1.0 g/kg, 2.0 g/kg and 3.0 g/kg of steel slag all can increase the production of soybean, radish, pepper, lettuce and asparagus lettuce, and these 5 vegetables all show the highest production at 2.0 g/kg of steel slag addition.Adding 2.0 g/kg and 3.0 g/kg of steel slag can increase the tomato production, and with no significant difference between this two treatments. This means that from the aspect of output, 2.0 g/kg of steel slag is the best dosage that fits for modifying acid vegetable soil.Compared with CK, adding more than 1.0 g/kg of steel slag can increase the N concentration of soybean. Addition of steel slag almost has no effect on the N concentration of mature radish tube. Only addition of 3.0 g/kg steel slag three times can increase the N concentration of pepper fruit. Addition of steel slag reduces the N concentration of lettuce and asparagus lettuce distinctly. And adding 2.0 g/kg and3.0 g/kg of steel slag can reduce the N concentration of tomato fruit. Adding 2.0g/kg and 3.0 g/kg of steel slag increases the P concentration of soybean, but has no effect on radish tube. The P concentration of pepper fruit decreases with increasing steel slag addition. Adding 1.0 g/kg and 2.0 g/kg of steel slag can increase the P concentration of asparagus lettuce obviously, and only adding 3.0 g/kg of steel slag can increase the P concentration of lettuce. The P concentration of tomato fruit reduces with the increasing of steel slag when the addition is more than 1.0 g/kg.Addition of steel slag almost has no effect on K concentration of soybean and radish tube, but increases the K concentration of pepper plant and fruit. Only adding 2.0g/kg and 3.0 g/kg of steel slag can reduce the K concentration of asparagus lettuce.The K concentration of lettuce increases with the increasing of steel slag, and that of tomato fruit is on the contrary. The Ca concentration of soybean increases and then decreases with the increasing of steel slag with a peak value at the dose of 2.0 g/kg.The Ca concentration of radish, pepper fruit, lettuce, asparagus lettuce and tomato fruit all increases with the increasing of steel slag. Addition of steel slag increases the Mg concentration of radish, but almost no effect on the Mg concentration of soybean, pepper, lettuce, asparagus lettuce and tomato.The soil samples with 3.0 g/kg of steel slag were used to detect the total As and Cd concentration. The results shows that the total As of the detected soil samples are between 1.5 mg/kg and 2.0 mg/kg, and the total Cd is about 0.1 mg/kg, which have no difference with CK and are below the first grade critical value of the national soil environment quality standard. On the other hand, the As and Cd concentration of the edible parts of supplied vegetables including soybean, radish, pepper, asparagus lettuce, lettuce and tomato are all below the minimum detection limit. This means that steel slag can be used to improve acid vegetable soil safely with proper dose andwithin a certain period.