![\"hombre-factor-formador-del-suelo\"](\"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-content\/blogs.dir\/42\/files\/145\/hombre-factor-formador-del-suelo.jpg\")
<\/p>\n<\/p>\n
En esta bit\u00e1cora hemos ya mostrado sobradamente como\u00a0el hombre ha transformado casi toda la edafosfera del planeta<\/span><\/strong>. \u00a1Nadie lo duda!. Ahora bien, se han venido utilizando argumentos peregrinos y falaces<\/strong> <\/span>a la hora de mostrar que el suelo es un recurso no renovable. Una de las majader\u00edas m\u00e1s utilizadas en la literatura cient\u00edfica nos viene a decir que \u201chacen falta unos mil a\u00f1os para que se forme 1 cm de suelo\u201d<\/strong>.<\/span> \u00a1As\u00ed llamamos la atenci\u00f3n del p\u00fablico y pol\u00edticos, so pena que a la postre, en el futuro, se nos tache de chapuceros, o peor a\u00fan, de tramposos. \u00a0Esta cifra es lo que en su d\u00eda denominamos<\/strong><\/span> un falso t\u00f3pico impregnante<\/span><\/a> de la literatura cient\u00edfica<\/strong>. Las razones<\/strong> <\/span>m\u00e1s que obvias son triviales<\/span><\/strong>. \u00bfTarda lo mismo en edafizarse una roca dura como la cuarcita que sedimentos no consolidados como lo son el loess o las cenizas volc\u00e1nicas?. Resulta dif\u00edcil de entender como los expertos han reiterado esta frasecita (porque de inferencia cient\u00edfica no tiene nada) \u201cad nausean<\/em>\u201d, a pesar de lo rid\u00edcula que resulta tal generalizaci\u00f3n<\/span><\/strong>. Del mismo modo, soslayamos la incorporaci\u00f3n de materiales acarreados por la\u00a0<\/strong><\/span>atm\u00f3sfera<\/strong><\/span>, que a menudo pueden ser mayores que los desprendidos por la roca madre<\/span><\/a> al edafizarse. Pero tambi\u00e9n el grado de alteraci\u00f3n<\/strong> <\/span>biogeoqu\u00edmica de los materiales parentales depende del clima<\/span><\/strong>, const\u00e1ndose de paso que la profundidad del regolito subyacente afecta al grado de edificaci\u00f3n de las rocas bajo el mismo<\/span><\/strong>. Obviamente no pretendemos ser exhaustivos, aunque debemos recordar que el elevamiento de tierras<\/span><\/a> y la continua adici\u00f3n de materia org\u00e1nica por el hombre al medio ed\u00e1fico, engrosando sus horizontes superficiales han sido muy frecuente desde los albores de la agricultura en todos los continentes<\/strong><\/span>, modificando dr\u00e1sticamente la estructura, din\u00e1mica y evoluci\u00f3n de los medios ed\u00e1ficos. \u00a0\u00bfY qu\u00e9 decir de la erosi\u00f3n<\/span><\/strong> y otros fen\u00f3menos degradativos?<\/strong>.<\/p>\n Del mismo modo, cuando analizamos el efecto de las pr\u00e1cticas humanas sobre el sistema suelo, solemos concentrarnos en los cent\u00edmetros superficiales, soslayando por completo el impacto sobre los m\u00e1s profundos<\/strong><\/span>.<\/p>\n Cient\u00edficos de EE.UU. han remuestreado en Iowa 82 perfiles tras 50 a\u00f1os de agricultura intensiva, analizando sus efectos hasta los 150 metros de profundidad<\/span><\/strong>, demostrando que en las partes bajas del perfil se producen cambios sustanciales, algunos de los cuales son incluso positivos <\/strong><\/span>(para la producci\u00f3n alimentaria), como el aumento de la materia org\u00e1nica<\/strong> <\/strong>y el descenso de la capa fre\u00e1tica<\/strong><\/span>, que como corolario pueden acelerar la edafog\u00e9nesis<\/span><\/strong>. \u00a0El estudio se encuentra en acceso abierto y pod\u00e9is leerlo en detalle, por lo que os mostramos m\u00e1s abajo, al final de este post, el modo de acceder a \u00e9l.<\/p>\n \u00bfHabr\u00e1n dado los investigadores de este estudio con la piedra filosofal que nos ayude a resolver el problema?. Lo dudo mucho<\/strong><\/span>, si bien se trata de un paso hacia adelante. \u00a0La cuesti\u00f3n dista mucho de estar resuelta, por cuanto<\/strong> <\/span>la l\u00f3gica dicta que la formaci\u00f3n de suelo es multifactorial, dependiendo de numerosos factores<\/span><\/a>, sinergias, retroalimentaciones positivas y negativas, etc. Dicho de otro modo, no podemos generalizar\/fijar fechas concretas<\/span><\/strong>, sino que adem\u00e1s debemos tener en cuenta la historia del territorio, e incluso efectos aparentemente tan nimios como la remoci\u00f3n de ciertos perfiles por la<\/span><\/strong> muerte\/ca\u00edda de un\u00a0 simple \u00e1rbol<\/span><\/a>.<\/p>\n As\u00ed mismo, tampoco podemos olvidarnos que las acciones humanas del pasado han alterado los ecosistemas a\u00e9reos de tal modo, que<\/strong> <\/span>estos afectaron la naturaleza de los suelos subyacentes. \u00a0Un caso palmario, entre otros muchos, deviene de la transformaci\u00f3n por el fuego y otras pr\u00e1cticas de antiguas selvas subtropicales ahora convertidas en sabanas. Pero hay m\u00e1s, mucho m\u00e1s<\/span><\/strong>.<\/p>\n Nadie duda, de que el impacto humano ha sido un factor formador del suelo<\/span><\/strong>, desde el nacimiento de loa agricultura, aunque algunos lo a\u00f1aden como un factor en la ecuaci\u00f3n \u00a0de Jenny<\/span><\/a> y otros lo soslayan. Sin embargo, hemos visto y lo seguiremos haciendo, como la transformaci\u00f3n de la edafosfera por la acci\u00f3n humana comienza a ser enorme ya en tiempos paleol\u00edticos<\/span><\/strong>, es decir miles de a\u00f1os antes del advenimiento de la agricultura. Seguimos sufriendo un sesgo agron\u00f3mico utilitarista que nos impide atisbar un palmo m\u00e1s all\u00e1 de nuestras narices<\/strong>. Leer literatura de otros campos resulta imperioso si deseamos quitarnos<\/strong><\/span> la boina de agr\u00f3nomos, dejar se seguir diciendo sandeces y comportarnos como una comunidad cient\u00edfica digna de llevar tal nombre.<\/p>\n Abajo os dejo con una nota de prensa, el abstract del art\u00edculo original, y como acceder al art\u00edculo de marras<\/em><\/span>.<\/p>\n Juan Jos\u00e9 Ib\u00e1\u00f1ez<\/strong><\/span><\/p>\n <\/p>\n Has farming become a soil-forming factor?<\/span><\/strong><\/p>\n August 28, 2015; By Madeline Fisher; \u00a0SSSAJ Research Highlights<\/span><\/p>\n From erosion to acidification to loss of organic matter, the impacts of agriculture on topsoil are well known. But an open access paper in the July-August 2015 issue of the Soil Science Society of America Journal now suggests that farming\u2019s effects on soil actually go much deeper.<\/span><\/p>\n Research in Iowa led by Jessica Veenstra (pictured here) suggests the impacts of farming on soil go much deeper than previosuly thought. Photo courtesy of Jessica Veenstra.<\/span><\/p>\n In a study that examined how soils across Iowa have evolved during 50 years of agricultural use, Iowa State University scientists Jessica Veenstra and Lee Burras uncovered the usual changes in surface soils that come with plowing and fertilizing, including acidification and damaged soil structure.<\/span><\/p>\n But by sampling down to 150 cm, or 5 ft, they unearthed a host of additional impacts, including a curious buildup of organic carbon deep in the soil profile.<\/span><\/p>\n The depth of the transformation supports the notion that human activities, such as farming, don\u2019t just make use of soil, but have joined climate, soil organisms, and other natural factors in forming soil, as well. It also suggests that agriculture affects soil more profoundly than previously thought.<\/span><\/p>\n \u201cI think most soil scientists are comfortable with the idea that the surface 30 cm (1 ft) of soil is changing drastically with agricultural practices,\u201d says Veenstra, now an assistant professor at Flagler College in Florida. \u201cBut our work shows that soils are changing in ways that perhaps we wouldn\u2019t have expected if we didn\u2019t look as deep as we did.\u201d<\/span><\/p>\n She explains that most studies focus on the uppermost soil horizons for two reasons: They\u2019re the critical layers for cultivating crops, and sampling deeper takes much more time and labor. But her and Burras\u2019 objective was different. \u201cOur interest was looking at the whole pedon [all the horizons in each soil type],\u201d Veenstra says, \u201cto get at this idea of how everything we do as humans is influencing how soil changes over time.\u201d<\/span><\/p>\n To address this, they resampled 82 sites across Iowa, representing 46 soil series originally described in the U.S. Soil Survey between 1943 and 1963. At the time of the survey, most of Iowa\u2019s soils were no longer under tallgrass prairie but were already being farmed\u2014a point that\u2019s key to the study goal.<\/span><\/p>\n \u201cWe didn\u2019t specify the \u2018native\u2019 condition and then see what agriculture has done to it,\u201d Veenstra says. \u201cOur initial conditions were agricultural because we were asking, how have these soils changed under agriculture during the last 50 years, and as we keep using the soil?\u201d<\/span><\/p>\n When the scientists compared the properties of their present day samples with baseline data from the original survey, they found evidence that agriculture is speeding up soil change to depths of 3 ft or more. Not surprisingly, they documented soil loss in most landscape positions. They also observed declines in nitrogen and organic carbon levels in surface soils.<\/span><\/p>\n \u00a0<\/span>Unexpectedly, though, losses of soil organic matter were confined to the top 50 cm (1.6 ft). In deeper layers, the researchers actually saw an accumulation of organic carbon. Why this deep soil carbon exists they aren\u2019t exactly sure. But their data also indicate that soils throughout Iowa are acidifying, with many sites now registering a pH below 5.5. The acidity may be causing organic matter near the surface to dissolve in water and move down into the profile, Veenstra explains, where it then precipitates out again.<\/span><\/p>\n Other changes included lowered water tables and a shift in soil structure from granular to blocky. But by far the most interesting finding was how deep the changes go. And most of them aren\u2019t good, Veenstra says. \u201cAccelerated erosion, accelerated acidification, loss of organic matter in surface horizons\u2014those all can have pretty negative effects on crop growth.\u201d<\/span><\/p>\n But if the evidence suggests that people are now a primary soil-forming factor, this means we can be a constructive force, as well. \u201cThere are all sorts of practices we can do,\u00bb Veenstra says, \u00abthat could have very positive effects on these soils to deep depths.\u201d<\/span><\/p>\n This story originally appeared in the Sept. 2015 issue of CSA News magazine.<\/span><\/p>\n ACSESS DL News<\/span><\/p>\n \u00a0SSSAJ Research Highlights<\/span><\/p>\n Abstract <\/strong><\/p>\n<\/span><\/p>\n