Chemical speciation of copper and manganese in solution of a copper-contaminated soil and young grapevine growth with amendment application

Copper(Cu)-based fungicide application to control foliar diseases in grapevine(Vitis vinifera L.)can increase soil Cu availability.Brazilian soils have high natural Cu and manganese(Mn)concentrations,increasing the potential for toxicity to grapevine plants.Application of amendment substances can reduce the concentrations of toxic chemical species of Cu and Mn in soil solution,especially for the soils grown with young plants.We evaluated the chemical speciation of Cu and Mn in soil solution and young grapevine growth using a contaminated soil with amendment application.Grapevine seedlings of Paulsen 1103rootstock were grown for 12 months on an old vineyard(>30 years of cultivation)soil without(control)and with vermicompost or limestone application.Grapevine dry matter,root morphological characteristics,and plant tissue Cu and Mn concentrations were evaluated.The cation and anion concentrations,dissolved organic carbon,p H,and chemical speciation of Cu and Mn in soil solution from different soil layers were analyzed.Vermicompost application did not reduce Cu and Mn phytotoxicity,and grapevine plants died after winter pruning.High soluble Mn concentration in soil(5.56 mg L-1in 0–45 cm soil layer)and Mn concentration in plant tissue at pruning(380.8 mg kg-1)might be the primary cause of plant death.Limestone application reduced Cu2+and Mn2+chemical species in soil solution,thereby increasing plant growth.The Cu2+and Mn2+species were negatively correlated(P<0.05)with grapevine shoot production at pruning(r=-0.92 and-0.97,respectively)and at the end of the trial(r=-0.73 and-0.51,respectively).Limestone application increased grapevine shoot and root dry matter production by 36%and 41%,respectively,while also presenting the highest root length and volume in the 5–10 cm soil layer.Limestone application is a viable and profitable alternative for reducing soil Cu and Mn availability and their phytotoxic effects.

Alkaline hydrolyzable nitrogen and properties that dictate its distribution in paddy soil profiles

Nitrogen(N) is a key nutrient for rice production, and its bioavailability in paddy soils is strongly coupled to soil organic matter(SOM) cycling. A better understanding of potentially available N forms in soil, such as alkaline hydrolyzable N(AH-N), and their depth distribution will support the development of best management practices to improve the N use efficiency of rice while minimizing adverse environmental effects. Fifteen rice(Oryza sativa L.) fields from Southern Brazil were selected, and stratified soil samples were taken to a depth of 60 cm before crop establishment. Selected soil physical and chemical properties were analyzed to evaluate their relationships with AH-N contents in the soil profile. The AH-N contents below 20 cm varied extensively(increased,reduced, or constant) compared with that above 20 cm. Although clay and clay + silt contents were highly correlated to AH-N for some soils, the major property dictating AH-N distribution by depth was total N(TN), as the correlation between TN and AH-N was mainly by direct effect. The proportion of TN recovered as AH-N across sites and depths presented high amplitude, and thus AH-N was not a constant N pool across depths, indicating that AH-N can be affected by soil management practices even when TN showed no major changes. The distinct distribution of AH-N across soil sampling sites and depths indicates that depths greater than 20 cm should be considered when calibrating the AH-N index for N fertilizer recommendations for flooded rice in Southern Brazil.