Most of the silicon absorbeb by plants remains deposited on the external part of the cell walls as a layer of amorphous silica (SiO2.nH2O), probably affecting straw mineralization in soils. An experiment was performed with the aerial part of oat plants, cultivated in nutrient solution with and without silicon addition, to evaluate this hypothesis. Dried aerial parts of oat plants tissue was mixed with soil or washed quartz sand and placed in PVC tubes. Distilled water was percolated through the […]

Carbon and nutrients released from the mineralization of organic materials can interact with mineral components changing their dynamics in the soil. In this study, mixtures of corn straw, kaolinite, synthetic goethite, and quartz sand were leached with water after 7, 15, 33, 68 and 113 days of incubation at room temperature. Concentrations of soluble carbon, calcium, magnesium, and potassium were measured and accumulated over time. After 200 days, the total carbon remaining in the mixture was quantified. Total calcium, magnesium, and potassium […]

A tilled soil has increased susceptibility to raindrop impact and sediment transport by laminar surface flow and splash, but after tillage the soil reconsolidates, increasing again its resistance. Thus, an experiment was conducted on a Hapludalf with Sandy loam soil surface, under no-tillage for eight years, to evaluate interrill erosion under different tillage methods. The experiment was totally randomized with six replicates. The treatments were recent conventional tillage (RCT), two-month consolidated conventional tillage (CCT), no-tillage with mulch (NTM) with 94% […]

This study, covering 12 cultivations, was carried out at Embrapa Rice & Beans Research Center, Santo Antônio de Goiás, Goiás, Brazil, in an Oxisol, under center pivot, for six consecutive years. The effects of four soil tillage systems and six crop rotations on bulk density and soil porosity were evaluated. The experiment was conducted in a completely randomized design, using a splitplot arrangement, with three replications. The tillage treatments were: moldboard plough/harrow disc, moldboard plough, harrow disc, and no-tillage. Tillage […]

Nitrogen top dressing period affects wheat grain yields and should occur at the stages when yield potential is established. In order to determine the critical stages related to N needs, field experiments were conducted at Estação Experimental Agronômica/UFRGS, Eldorado do Sul (RS), Brazil, in 1993, 1994 and 1995. Wheat cultivars BR 23 (1993 and 1994) and Embrapa 16 (1995) were sown by the end of June at 300 seeds m-2. Nitrogen treatments (40 kg ha-1) were applied at the following stages: (a) plant emergence, (b) […]

In Brazil, upland rice is cultivated mainly on cerrado soils, which, due to their highly weathered degree, present low pH, low base saturation and low ratio of Si oxides of Fe and Al. A greenhouse experiment was conducted to evaluate the response of upland rice to calcium silicate as well as its effect on correcting soil acidity. The treatments consisted of six levels of SiO2 (0; 125; 250; 375; 500 and 625 mg kg-1 of soil) as of wallastonite, Wansil-10 (50% of […]

The estimative of the maximum surface runoff volume is fundamental to design several types of hydraulic structures as, for example, level terracing systems. The incorrect estimative of the surface runoff volume causes a wrong design of these systems and when overestimated present high installation cost. Considering these aspects, the present study aimed to compare the values of the surface flow maximum volume obtained by the empiric method of the curve number and developed by the USA Soil Conservation Service, with […]

The study of the effects of soil tillage systems on some physical and chemical properties of a Typic Paleudal and on cassava yield (Manihot esculenta, Crantz) was carried out in the northwest of the state of Paraná, Brazil in 1994/95 and 1996/97. Three soil tillage systems were used: (a) no-tillage; (b) minimum tillage (field cultivator and disc harrowing); and, (c) conventional tillage (mouldplowing and disc harrowing). A randomized complete block experimental design with six replications was used. Higher macroporosity values in the 0.10 m […]

An experiment was carried out under greenhouse conditions to evaluate the effects of arbuscular mycorrhizal fungi (AMF) and, or rhizobium inoculation, with the addition of industrial waste from lactic acid production (Ferkal), on the growth of Mimosa caesalpiniaefolia. Plastic pots of 6 L of capacity were used, filled with degraded soil from clay extraction areas with four levels of the Ferkal residue (0, 50, 100 and 200 g dm-3). Six microbiological treatments were conducted: indigenous AMF; AMF Glomus clarum; rhizobium; indigenous AMF + Rhizobium; […]

A set of 874 erosive individual rainfall occurrences was selected from a continuous serie of twenty-three years of recording rain gauge data. All the selected rainfall occurrences were analized. The rainfall erosivity factor computed was 7074 MJ mm ha-1 h-1 y-1, which is expected to occur at least once every 2.33 years, with a probability of occurrence of 42.92%. The values of the annual erosivity indexes at that site expected for the return periods of 2, 5, 10, 20, 50, and 100 years, were respectively 6,696, 8,730, 10,076, […]