Rullán-Vázquez, Luis A.

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    Descomposicion de hojarasca de crotalaria (Crotalaria juncea), millo perla (Pennisetum glaucum), solas y en mezcla en un sistema de produccion de berenjenas.
    (2018) Rullán-Vázquez, Luis A.; Valencia-Chin, Elide; College of Agricultural Sciences; Tirado Corbalá, Rebecca; Linares Ramírez, Angela; Department of Crops and Agro-Environmental Sciences; Chávez Jauregui, Rosa
    Two experiments were conducted at the Agricultural Experimental Sub-station of Lajas, University of Puerto Rico. The first one was directed towards evaluating dry matter yields (DMY) and the decomposition dynamics [nitrogen (N), organic matter (O.M.), organic carbon (O.C.) and C:N ratio] of cover crops tissue at two ages (6 and 8 weeks old) when exposed above and under soil surface. The two cover crops evaluated were Crotalaria juncea (crotalaria), Pennisetum glaucum (pearl millet), and a mix 50:50 (crotalaria:millet). Cover crops were sown on October 2015 with a ‘Brillion’ seeder at a density of 10-12 kg ha-1 in a randomized complete block design with four repetitions. There was no interaction (cover crops x age), nor significant difference (p>0.05) for crops on DMY between the two ages. N percentage differed (p<0.05) between cover crops where crotalaria obtained 4.84%, higher than pearl millet (3.64%). The N percentage was converted to 52 and 88.4 kg N ha-1 for the crotalaria at 6 and 8 weeks, respectively. For millet, 59.8 and 68 kg N ha-1 and 77.2 and 83.4 kg N ha-1 for the mix 50:50. Regarding litter decomposition, an interaction (p<0.05) was found between cover crops age and plant litterbag position. Higher decomposition constants (k) were found for below ground bags at 6 and 8 weeks old tissue (0.269 and 0.188, respectively). There was also significant difference (p<0.05) in k for crops where millet presented the highest value (0.220). For O.M. and O.C. a triple interaction was found, for both variables, where the lowest values were for 6 weeks old tissue (above ground), collected after 2 weeks of placement. Values fluctuated from 62.7 to 80.4% for O.M. and 31.4 to 40.2% for O.C. Also, significant difference (p<0.05) was found between crops where crotalaria presented the highest values for O.M. and O.C. (74.5 and 37.2%, respectively). The second experiment integrated the results from the first essay to evaluate the production and yield of a vegetable crop (Solanum melongena cv. Rosita) under treatments from both cover crops and the mix 50:50 used as residues. Comparing DMY at 8 weeks from the cover crops between the first and second experiment, significant differences (p<0.05) were observed where in the latter all values were higher as was the N contribution. When analyzing eggplant yields, significant differences (p<0.05) were also found between treatments with cover crops in both fruits per hectare and total weight (kg ha-1). Under crotalaria, the eggplant presented the highest yield with an estimate of 88,543 fruits per hectare and 19,029 kg ha-1 between the cover crops used. It was demonstrated that cover crops, especially legumes, can supply part of the nutrients (ex. N) required by vegetable crops. However, it’s imperative to try and synchronize cover crops decomposition and nutrient release with the vegetables phase of higher nutrients demand to ensure optimal yields and production. More studies are needed integrating cover crops in vegetables production systems to try and understand decomposition dynamics, nutrients release and mineralization.