Faithin Omaha eBook Collection

Download or read book Evaluation of the Nitrogen Supplying Potential of Legumes Placed on the Surface Or Incorporated in a Brazilian Oxisol written by Francisco José Sá Antunes Costa and published by . This book was released on 1988 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based en several experiments, legume green manures are excellent sources of nitrogen for crop production in the cerrado. However, the variability in results among species/varieties and managements illustrate that considerable research must be done before green manuring can be recommended to farmars with a reasonable assurance that the results will be acceptable and consisten. Thus, two experiments, one in the greenhouse and other in the field, were conducted to screen legumes and managements in terms of inorganic nitrogen accumulation in the soil. Both experiments used the same, a typic haplustox of the cerrados region of central Brasil, and the same properties were measured. Ammonium and nitrate levels of the soil samples, and dry matter and nitrogen content of the remaining undcomposed residue on the surface were measured. The fallow soil method was used in both experiments, which were conducted at CPAC/EMBRAPA, Brazil in 1986. Fresh chopped leaves of mucuna aterima (piper and tracy) merr. were surfae placed or incorporrate in pots of 4.5 kg soil in the greenhouse. This experiment was conducted for 178 days. Fresh chopped aboveground parts of canalia ensiformes (L) DC., crotaleria paulina schrank, lablab purpureus (L). sweet, and mucuna aterrima (piper and tracy) merr. were surface placed or incorpoated in a field experiment in the beginning of the season. The experiment was conducted for 168 days with irrigation. In the greenhouse experiment the legume incorporated treatment had an inorganic nitrogen acculation 60 % higher than the surface placed legume treatment. The nitrification was so intense that after 35 days all of the inorganic nitrogen was in the form of nitrate. After 3 and 178 days, 15 and 45 %, respectively of the surface applied nitrogen was not recovered as inorganic in the soil or residue on the soil surface. One can speculate that some of this unaccounted for nitrogen was lost by ammonia volatilization. There was no string evidence that the incorporated legume decomposed faster than suface placed legume. In the field experiment the net nitrogen mineralization of all legumes was so low that there was no significant difference between the acculated inorganic nitrogen of the legume treatments and chek, except for incorpated c.ensiformes. The net nitrogen mineralization of incorporated c.ensiformes, c.paulina, L.purpureus, and m.aterrima were 45, 22, 13, and 15 % of the initial amounts of nitrogen applied as incorporated legume, respectively. There was no signicant difference between the two managements (incorporation or surface placement), except for c.ensiformes. The acculation of mineral nitrogen was very rapid for the firtst 30 days, relatively slow for 30 to 100 days and almost zero between 100 and 168-178 days for both experiments. The controlled irrigation experiment in the dry season was successful in avoiding nitrogen nitrogen leaching to soil below the sampling depth.