Growth and Dry Matter Yield of Maize (Zea mays L.) and Ryegrass (Lolium perenne L.) Plants as Affected by the Application of Liquid and Solid Organic Amendments in a Cu Contaminated Soil

The main objective of this study was to evaluate the effect of the application of two solid and one liquid organic amendments (OA), i.e., turkey manure, vineyard compost, and compost-derived humic acids (HA), on the growth and dry matter (DM) yield of maize and ryegrass plants grown in pots (5 L and 2 L) using a contaminated soil. Maize and ryegrass plants were consecutively cultivated during the experimental period (140 days) using a complete random design. Amendments were applied 10 days before the first crop (maize), at three different application rates, and both plant species were chemically fertilized (NPK). Control treatments with and without chemical fertilization were also included. Aerial dry matter (DM) yield of maize was enhance by manure and compost addition in comparison to the fertilized control, while HA had a negative impact on the DM production due to increased soil electrical conductivity (EC). In average, compost and manure applications increased maize DM about 1.2 and 2.7 fold over the control, respectively. DM yield of ryegrass was proportionally increased by the C rate for the three amendments, with few significant differences (p<0.05) among them at the higher application rates. In average, compost, manure and HA applications increased ryegrass DM about 1.5, 1.9, and 1.4 fold over the control. Significant modifications (p<0.001) of the soil available Cu were noted. Correlation analyses indicated that the lower DM production of plants was related to a higher damage of root membranes (malondialdehyde [MDA] test) induced by the higher levels of DTPA-Cu. The observed differences in DM would be also explained by the input of different nutrients (like N-NH4) contained in the OA, especially in the manure. Using a stepwise procedure, a regression model was generated for predicting the total maize + ryegrass DM production as a function of soil properties. This model incorporated as predictive variables: DTPA-Cu and FA-C.