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- Assessment of Mineralized Nitrogen During Maize Growth Succeeding Different Winter Cover Crops in the Mediterranean EnvironmentPublication . Perdigão, Adelaide; Pereira, José L.S.; Moreira, Nuno; Trindade, Henrique; Coutinho, JoãoBackground: Understanding soil nitrogen (N) dynamics is essential to find alternative N sources and improve N use efficiency in agriculture. Objective: The aim of this study was to assess N mineralization rates from residues of winter cover crops, during maize crop season, under Mediterranean conditions. Methods: A field experiment was carried out from May to September in central Portugal, with four replications, two sowing dates of cover crops (15/10/2011 and 29/11/2011) and three cover crops residues (balansa clover, ryegrass and yellow lupine) that were incorporated in the soil. Plots were cropped with local maize and net N mineralization was measured during the crop cycle, using soil cylinders placed inside micro-perforated polyethylene bags. Results and Discussion: Early sowing of the cover crops residues increased the NH4+ and NO3- contents in the soil. Yellow lupine residue had the highest rate of daily N mineralization (0.71 mg N kg-1 day-1). For all treatments, the highest mineralization rate was found in the last incubation period, ranging between 0.78 mg N kg-1 day-1 and 1.84 mg N kg-1 day-1, both for balansa clover, from the second and the first sowing date, respectively. Conclusion: The present study suggests that, under Mediterranean field conditions, cover crops residue of Italian ryegrass, balansa clover and yellow lupin can be used as a nitrogen source namely for sustainable maize crops.
- Effect of Different Tannery Sludge Composts on the Production of Ryegrass: A Pot ExperimentPublication . Perdigão, Adelaide; Marques, Francisco; Pereira, José L.S.Background: Tannery industry produces high amounts of nutrient rich sludges that can be used as organic fertilizers. Objective: The aim of this study was to evaluate the fertilizing potential of composted tannery sludge. Methods: A pot experiment was carried out with ryegrass (Lolium perenne L.) to test two different composts: 2.0 kg dry matter (DM) tannery fatty sludge + 1.5 kg DM sheep manure + 1.5 kg DM wheat straw (Compost 1) and 2.0 kg DM tannery sludge + 1.5 kg DM sheep manure + 1.5 kg DM wheat straw (Compost 2). Five treatments, with three replicates each, were assigned: Control (C); Compost 1 at 6 t (C1-6) and 12 t (C1-12) DM ha-1; Compost 2 at 6 t (C2-6) and 12 t (C2-12) DM ha-1. Each treatment was applied in a pot and mixed with 5 kg of sieved soil (<2 mm). Results: Results showed that production of DM ranged between 1.2 t DM ha-1 for C1-6 and 2.4 t DM ha-1 for C2-12. The highest B, Na and N levels in ryegrass was observed in C2-12, with 175 mg kg-1 DM, 9 g kg-1 DM and 30 g kg-1 DM, respectively. At the end of the experiment no differences were observed between treatments for C, N, P2O5, and K2O levels. Differences were observed at Zn level ranged between 101 mg kg-1 DM for C1-6 and 71 mg kg-1 DM for C2-12. Conclusion: The C2-12 treatment was the best because induces higher DM production and nutrients in ryegrass and without dangerous concentration of heavy metals in soil. Composted waste from the tannery industry is a good source of nutrients for agriculture.