Fulvic acid displaces manure to improve soil in vegetable greenhouse

Abstract

Acid soil has led to a significant decrease in vegetable yield in high-yield greenhouse vegetable production system. Chicken manure and fulvic acid (FA) application experiment was conducted to evaluate the effects on chemical properties of soil in vegetable greenhouse so as to confirm whether FA could replace chicken manure in acid soil amelioration under the same addition levels of nutrient, when compared to the effect of chemical fertilizers application alone on acid soil improvement. The results showed that the pH of soil added with chicken manure and FA, respectively, increased from the original value of 5.4 to 5.99 and 6.32 at the end of the experiment, while soil pH applied only with chemical fertilizers decreased to 5.43. Correlation analysis indicated that cation exchange capacity (CEC) of soil was positively correlated with soil pH buffering capacity. The peak values of soil CEC and pH buffering capacity occurred in April each year and subsequently tended to decrease in August and December throughout the experiment. Data demonstrated that chicken manure and FA in combination with soil contributed to soil base saturation that increased from 26.5%, 33.8% to 36.7%, 45.9% in chicken manure and FA treated soil during December 2011 to December 2012, respectively; however, chemical fertilizers displayed an adverse effect on soil base saturation that decreased from 17.1% to 5.6% on the same time period. Exchangeable aluminum (Al) concentration showed a weak but significant increase by 5.2% on August 2012 in comparison to April 2012, as chemical fertilizers were added into soil alone. Unlike to chemical fertilizer, chicken manure and FA significantly decreased soil exchangeable Al concentration from the original value of 5.37 cmol kg−1 to 4.56 and 4.22 cmol kg−1 at the end of experiment respectively. Compared to total yield treated solely with chemical fertilizers, chemical fertilizers combination with chicken manure or FA resulted in an increase in total yield in 2011 and 2012. Although chicken manure and FA possessed the same trend of improving acidic soil in vegetable greenhouse, a greater contribution was attributed to FA due to its lower mineralization rate of organic matter. Therefore, it was suggested that FA could completely displace chicken manure in improvement in acidic soil in vegetable greenhouse.