Influence of cattle or pig manure fertilization on zinc in runoff from sloped vegetable fields

Abstract

We investigated the runoff of zinc (Zn) from sloped vegetable fields fertilized with cattle or pig manure. The Zn concentration in the soil increased on fertilization with manure, particularly pig manure. The Zn was concentrated in silt and clay. The concentration of dissolved Zn in runoff was low and relatively constant regardless of the rate of runoff or the suspended solids concentration. On the other hand, the concentration of particulate Zn increased as runoff increased and was correlated with the suspended solids concentration. Heavy downpours strongly influenced runoff loads of particulate Zn. Total Zn loads measured during 5 h of up to 120 mm of rainfall were 77% of the annual Zn loads in the fields without manure, 83% with pig manure, and 90% with cattle manure. The concentration of total Zn in the runoff was higher from vegetable fields fertilized with manure than without manure. However, manure significantly decreased runoff. Therefore, the addition of manure decreased the Zn runoff load. In a vegetable field fertilized with cattle manure, the annual Zn runoff load is decreased to one-third of that in fields without manure.