Fertilizer vs. organic matter contributions to nitrogen leaching in cropping systems of the Pampas: 15N application in field lysimeters

Abstract

Nitrogen (N) export from soils to streams and groundwater under the intensifying cropping schemes of the Pampas is modest compared to intensively cultivated basins of Europe and North America; however, a slow N enrichment of water resources has been suggested. We (1) analyzed the fate of fertilizer N and (2) evaluated the contribution of fertilizer and soil organic matter (SOM) to N leaching under the typical cropping conditions of the Pampas. Fertilizer N was applied as 15 N-labeled ammonium sulfate to corn (in a corn/soybean rotation) sown under zero tillage in filled-in lysimeters containing two soils of different texture representative of the Pampean region (52 and 78 kg N ha -1 , added to the silt loam and sandy loam soil, respectively). Total fertilizer recovery at corn harvest averaged 84 and 64% for the silt loam and sandy loam lysimeters, respectively. Most fertilizer N was removed with plant biomass (39%) or remained immobilized in the soil (29 and 15%, for the silt loam and sandy loam soil, respectively) whereas its loss through drainage was negligible (<0.01%). We presume that the unaccounted fertilizer N losses were related to volatilization and denitrification. Throughout the corn growing season, subsequent fallow and soybean crop, which took place during an exceptionally dry period, the fertilizer N immobilized in the organic pool remained stable, and N leaching was scarce (7.5 kg N ha -1 ), similar at both soils, and had a low contribution of fertilizer N (0-3.5%), implying that >96% of the leached N was derived from SOM mineralization. The inherent high SOM of Pampean soils and the favorable climatic conditions are likely to propitiate year-round production of nitrate, favoring its participation in crop nutrition and leaching. The presence of 15 N in drainage water, however, suggests that fertilizer N leaching could become significant in situations with higher fertilization rates or more rainy seasons.

Nitrogen mineralization, plant uptake and nitrate leaching following the incorporation of (15N)-labeled cauliflower crop residues (Brassica oleracea) into the soil: a 3-year lysimeter study

“…It thus suggests that gaseous N losses (e.g., volatilization and denitrification) were low, though we lacked the data to estimate them. This also confirms that the N (fixation + immobilization) provided by the turnover of the crop residue N is located mainly in the top soil layer, as previously shown in other experiments (Portela et al 2006). …”

“…A correction of 0.0025% was applied to the values of atom % excess in non-labeled plant biomass and soil to account for natural abundance, which was slightly higher than that of the air (0.3663%) (Morvan 1999;Portela et al 2006). The percentage of N from the 15N-labeled cauliflower residues recovered in each compartment (aboveground plant biomass, top soil layer, and drainage water) was calculated as:…”

Impacto antrópico en la calidad del agua superficial de la cuenca media del Arroyo Claromecó, Argentina

“…Sin embargo, y como ocurrió a lo largo de toda la región pampeana, en los últimos años se ha producido una tendencia a prolongar los ciclos agrícolas con respecto al período de uso ganadero; pero también, se han incorporado nuevas superficies con baja aptitud para la actividad agríco-la (Forján, 2004;Portela et al, 2006). Este uso más intensivo conlleva una aplicación cada vez más recurrente de fertilizantes nitrogenados y herbicidas y cabe destacar que estos últimos se aplican a través de fumigaciones aéreas, cuando las condiciones de suelo son de humedad severa.…”

Fertilização nitrogenada no consórcio milho - braquiária em solos de clima tropical úmido no sistema de integração lavoura-pecuária

“…Esta observação deve-se ao maior potencial de volatilização da aplicação a lanço na semeadura, em relação ao mesmo modo feito em cobertura recuperou, em média, 88% no sistema solo planta, quantidade maior do que o N incorporado, em que a recuperação foi, em média, 67%. Esta diferença deu-se por dois motivos: (i) pela eficiência da aplicação a lanço, com pequena perda por volatilização nas adubações feitas na semeadura, e praticamente zero na adubação em cobertura, (ii) por causa da maior imobilização do N no solo com a distribuição a lanço (TOMAR; SOPER, 1981;CARTER;RENNIE, 1984;NYBORG, 1991;MALHI et al, 2001 TIMMONS, 1994;FERNANDES;CARVALHO, 2006;PORTELA et al, 2006;JAYASUNDARA et al, 2007;GHIBERTO et al, 2011;RIMSKI-KORSAKOV;RUBIO;LAVADO, 2012). No Latossolo de Uberlândia a lixiviação pode ter sido maior por tratar-se de solo bem drenado, devido à elevada porosidade, em virtude da estrutura granular de tamanho muito pequeno, grau fraco e consistência macia quando seco.…”

“…Com esta técnica consegue-se maior produção de massa vegetal para a cobertura do solo (BALDÉ et al, 2011;BORGHI et al, 2012;CECCON et al, 2013;CRUSCIOL et al, 2013), realizar o estabelecimento de pastagens para exploração da criação de animais FISHER;TOZER;ABRECHT, 2012;BORGHI et al, 2013), redução da perda de solo no processo erosivo (JOSHI;TAMBE, 2010;MONTENEGRO et al, 2013), reduzir a ocorrência de plantas daninhas (DERKSEN et al, 2002;HAUGGAARD-NIELSEN et al, 2006;HILTBRUNNER et al 2007;UCHINO et al, 2009;KOSINSKI et al, 2011;CONCENÇO et al, 2012;UCHINO et al, 2012;AMOSSÉ et al, 2013;SCOPEL et al, 2013), manter a área vegetada para realizar ciclagem de nutrientes e redução das perdas de nutrientes nos períodos de entressafra (STROCK;PORTER;RUSSELLE, 2004;QI et al, 2011;RESTOVICH;ANDRIULO;PORTELA, 2012;FRASER et al, 2013;HASHEMI et al, 2013), aumentar a eficiência de uso da terra e recursos naturais (água, luz e nitrogênio) (ZHOU et al, 2000;HAUGGAARD-NIELSEN;AMBUS;JENSEN, 2001JENSEN, , 2003BEDOUSSAC;JUSTES, 2010aJUSTES, , 2010bBALDÉ et al, 2011;LITHOURGIDIS et al, 2011;YANG et al, 2011;YANG;DONG, 2011;MAO et al, 2012;JANNOURA;…”