000			040100000a22006370004500
903			_aE
904			_aBCO
905			_aC
908			_aJ
909			_aAS
912			_aEn
912			_aEn
914			_aSILVI
914			_aRIBRE
914			_aAG
082	0	4	_a23031
100	1		_966132 _aEwel, J.J.
100	1		_992143 _aMazzarino, M.J.
100	1		_948343 _aBerish, C.W.
260			_c1991
041	0		_aEn
520			_aThe fertility of a volcanic-ash derived Inceptisol at a site in the humid tropics of Costa Rica was monitored for five years. Four treatments were established in a randomized block design with six blocks: a sequence of monocultures (two crops of maize (Zea mays) followed by cassava (Manihot esculenta), then the tree species Cordia alliodora), successional vegetation, a mimic of successional vegetation that was physiognomically similar to the model but shared no species with it, and a species-enriched version of successional vegetation. In addition, one plot was maintained free of vegetation. Species-rich successional vegetation was effective at maintaining soil fertility, although general trends of soil-nutrient decline benealth all treatments, presumable because of plant uptake. It proved possible to imitate the fertility-maintaining characteristics of successional vegetation by creating an equally species-rich community of fertility was no enhanced by further species enrichment. Successive peaks of nitrate-nitrogen in soil solution, extractable phosphorus, and extractable potassium occurred during the first year, perhaps driven by an early increment of organic matter from postburn debris and roots. Organic matter, total nitrogen, and extractable sulfur were remarkably stable during the 5-yr period. Depletions of castions, decreases in effective cation exchange capacity (CECe), and increases in acid saturation were related to treatment in the following order: bare soil>monoculture>the three diverse, successional communities. In the bare-soil plot, fertility decreased dramatically: there was a net loss of exchangeable cations and inorganic nitrogen, the phosphorus-fixation capacity increased, and acid saturation reached a potentially toxic 86 percent. At the start of the study, three of the blocks had soil with lower pH, lower CECe, and higher acid saturation. During the study this less fertile soil lost porportionally more cations and increased more in acid saturation and phosphorus-fixation capacity. The less fertile soil under monocultures proved exceptionally vulnerable to loss of fertility; after 5 yr under monocultures, for example, acid saturation reached 38 percent in the more fertile soil and 75 percent in the less fertile soil. In the species-rich communities, however, changes in soil fertility were far less marked.
650	1	4	_9165625 _aSUELOS
650	1	4	_9156042 _aNITROGENO
650	1	4	_9147821 _aFERTILIDAD DEL SUELO
650	1	4	_9133936 _aABONOS
650	1	4	_9167494 _aTROPICO HUMEDO
650	1	4	_9148453 _aFOSFORO
650	1	4	_9156299 _aNUTRIMENTOS
650	1	4	_9165551 _aSUCESION NATURAL
650	1	4	_9168904 _aZEA MAYS
650	1	4	_9153830 _aMANIHOT
650	1	4	_9142337 _aCORDIA ALLIODORA
650	1	4	_92064 _aCOSTA RICA
691			_9156032 _aNITROGEN
691			_9165093 _aSOIL FERTILITY
691			_9147879 _aFERTILIZERS
691			_9158339 _aPHOSPHORUS
691			_9168904 _aZEA MAYS
691			_9153830 _aMANIHOT
691			_9142337 _aCORDIA ALLIODORA
691			_aCOSTA RICA _92064
692			_aAZOTE
692			_aFERTILITE DU SOL
692			_aENGRAIS
692			_aPHOSPHORE
692			_aZEA MAYS
692			_aMANIHOT
692			_aCORDIA ALLIODORA
692			_aCOSTA RICA
773	0		_tEcological Applications (FAO) _d1991 _gv.1(3) p.289-302
040			_aCR-TuBCO _cCR-TuBCO _bEs
245	1	0	_aTropical soil fertility changes under monocultures and successional communities of different structure
942			_cANA
003			CR-TuBCO
999			_c51678 _d51678