Nivaldo Eduardo Rizzi

Perdas de solo e água e qualidade do escoamento superficial associadas à erosão entre sulcos em área cultivada sob semeadura direta e submetida às adubações mineral e orgânica

Among conservation tillage methods, no-till has shown to be the most effective in reducing soil losses caused by rainfall erosion, but with considerable data variation regarding water loss. Considering these aspects, this study was carried out with the objective of evaluating soil and water losses, the chemical demand of oxygen (CDO), electrical conductivity, and the pH of surface runoff, associated with interrill erosion under simulated rainfall. The field study was conducted in October 2003 in Marechal Cândido Rondon county, western Parana state, Brazil, in an area cultivated under no-till and that received chemical and organic fertilization. The soil is a clayey Oxisol (eutroferric Red Latosol) with 0.045 m m-1 slope. On small plots (1.0 x 1.0 m) with pre-wetted soil, the following rainfall intensities were applied by a rotating-boom rainfall simulator: 70.0, 60.0 and 120.0 mm h-1, during 20 min each, with time intervals of 30 min in-between. The treatments consisted of: (a) chemical fertilization, with nitrogen, phosphorous, and potassium _ NPK; (b) organic fertilization with liquid swine manure_ DLS, and (c) no-fertilization (control treatment) _ T. The highest soil and water losses in the experiment were observed in the DLS treatment, regardless of the simulated rains (except soil loss in the last rain, which reached the highest value in the study); the results of NPK and control T treatments were similar. The highest values of chemical oxygen demand, electrical conductivity and pH of surface runoff were also observed in the DLS treatment, while the lowest values occurred in the T treatment (except the chemical oxygen demand in the NPK treatment, which was also low), regardless of the simulated rains.

Phosphorus loss by surface runoff in no-till system under mineral and organic fertilization

The no-till system has been intensively used in the state of Parana, Brazil, and it has increased the nutrients level at the soil surface. This has contributed for nutrient losses via runoff and consequently, off-site water pollution. The objective of this study was to evaluate phosphorus loss in surface runoff by simulated rainfall on an Oxisol, under no-till system following application of mineral fertilizer and liquid swine manure. Nitrogen, soil and water losses from the same study are reported in a separated paper. The application of liquid swine manure, compared with mineral fertilization, increased runoff concentration of total P, particulate P and dissolved reactive P by 193%, 111% and 506%, respectively, averaged for all rainfall intensities. Independently on the fertilizer source, the highest rainfall intensity provided the greatest concentration and loads of P in runoff.

Mobilidade de íons em solo sob sistema de semeadura direta submetido às adubações mineral e orgânica

A retencao, no perfil do solo, de elementos minerais aplicados em sua superficie e fundamental para manter a qualidade da agua e diminuir prejuizos economicos e ambientais. Este trabalho avaliou a mobilidade do K, Ca, Mg, teores de Al e materia orgânica, as alteracoes de pH, em Latossolo Vermelho eutroferrico cultivado sob sistema de semeadura direta, bem como a demanda quimica de oxigenio (DQO) da agua de percolacao. A mobilidade foi medida em colunas de solo com estrutura preservada e submetidas a adubacao mineral (100 kg ha-1) ou orgânica (150 m3 ha-1). Com uso de adubo mineral houve maior lixiviacao de K, Ca e Mg, mesmo com maior quantidade de K aplicado via adubo orgânico do que via adubo mineral. A DQO da agua percolada no sistema com adubacao orgânica foi menor do que com adubacao mineral. Os teores de Ca2+ e de Mg2+ foram maiores na camada de 0 a 2,5 cm, principalmente para a adubacao orgânica. O adubo orgânico nao aumentou o teor de materia orgânica no solo, porem, na camada de 0 a 2,5 cm, elevou o pH do solo em uma unidade e neutralizou o Al3+. Os resultados deste trabalho mostram o efeito depurador do solo sobre aguas contaminadas, evidenciando os beneficios economicos e ambientais que poderao advir com a infiltracao no solo da agua de enxurrada que venha a se formar em lavouras.

Perda de nutrientes via escoamento superficial no sistema plantio direto sob adubação mineral e orgânica

The no-tillage system, has contributed to improvements in agricultural soils, among them the like increases in nutrient concentrations.of mineral elements in soil. However, it has been found that this increase concentration occurs mainly in the first few centimeters of the superficial top layer and so risks of nutrient losses by runoff, and associated of the soil, which concurs for losses of mineral elements through of runoff, with economic and environmental damages, are high. This study evaluated the total concentration, in runoff, of mineral elements potassium (K), calcium (Ca), magnesium (Mg) and copper (Cu) in total form and the soluble and particulate concentration form of K, in runoff caused to simulated rainfall of different intensitiesy applied over soil under no-till system and submitted to simulated after application of organic or mineral fertilizers in no-till soil. The fertilizers did not affect the concentration of mineral elements studied nutrients in runoff, except in condition of more high intense rainfall and soil under after organic manure application, which promoted runoff with showed the higher highest concentration of soluble and total K. Independent Irrespective of the type of fertilizers utilized type, the rainfall of higher intensity resulted in higher concentrations of all the mineral elements and forms studied, either in total, soluble or particulate form, evidencing the economic and environmental benefices, risks and suggesting that with the adoption of practices for runoff contention of runoff practices must be adopted , even in tilled croplands areas managed under no-till system.