Winter pasture and cover crops and their effects on soil and summer grain crops

The objective of this work was to evaluate the effect of winter land use on the amount of residual straw, the physical soil properties and grain yields of maize, common bean and soybean summer crops cultivated in succession. The experiment was carried out in the North Plateau of Santa Catarina state, Brazil, from May 2006 to April 2010. Five strategies of land use in winter were evaluated: intercropping with black oat + ryegrass + vetch, without grazing and nitrogen (N) fertilization (intercropping cover); the same intercropping, with grazing and 100 kg ha-1 of N per year topdressing (pasture with N); the same intercropping, with grazing and without nitrogen fertilization (pasture without N); oilseed radish, without grazing and nitrogen fertilization (oilseed radish); and natural vegetation, without grazing and nitrogen fertilization (fallow). Intercropping cover produces a greater amount of biomass in the system and, consequently, a greater accumulation of total and particulate organic carbon on the surface soil layer. However, land use in winter does not significantly affect soil physical properties related to soil compaction, nor the grain yield of maize, soybean and common bean cultivated in succession.

Soil Stabilization With Chemicals, Iowa Highway Research Board Bulletin No. 22, 1960

In the search for new soil stabilizing agents the effects of six organic cations on plastic limit, liquid limit, shrinkage limit, air-dry strength and rate of slaking of a highly plastic clay subsoil were studied. In all cases the plasticity index and shrinkage were reduced by the treatments. The air-dry strength was lowered in varying degree, which was the only undesirable effect noted. With one exception resistance to slaking was improved. It is concluded that large organic cations show promise as possible stabilizing agents for highly plastic fine-grained soils.

Correlation of physical and chemical attributes of soil with sugarcane yield

The objective of this work was to evaluate the correlation between sugarcane yield and some physical and chemical attributes of soil. For this, a 42‑ha test area in Araras, SP, Brazil, was used. Soil properties were determined from samples collected at the beginning of the 2003/2004 harvest season, using a regular 100x100 m grid. Yield assessment was done with a yield monitor (Simprocana). Correlation analyses were performed between sugarcane yield and the following soil properties: pH, pH CaCl2, N, C, cone index, clay content, soil organic matter, P, K, Ca, Mg, H+AL, cation exchange capacity, and base saturation. Correlation coefficients were respectively ‑0.05, ‑0.29, 0.33, 0.41, ‑0.27, 0.22, 0.44, ‑0.24, trace, ‑0.06, 0.01, 0.32, 0.14, and 0.04. Correlations of chemical and physical attributes of soil with sugarcane yield are weak, and, per se, they are not able to explain sugarcane yield variation, which suggests that other variables, besides soil attributes, should be analysed.

Biochar effect on the mineralization of soil organic matter

The objective of this work was to verify whether the addition of biochar to the soil affects the degradation of litter and of soil organic matter (SOM). In order to investigate the effect of biochar on the mineralization of barley straw, soil was incubated with 14C-labelled barley straw with or without unlabelled biochar. To investigate the effect of straw on the mineralization of biochar, soil was incubated with 14C-labelled biochar with or without straw. In addition, to investigate the effect of biochar on old SOM, a soil labelled by applying labelled straw 40 years ago was incubated with different levels of biochar. All experiments had a control treatment, without any soil amendment. The effect of biochar on the straw mineralization was small and nonsignificant. Without biochar, 48±0.2% of the straw carbon was mineralized within the 451 days of the experiment. In comparison, 45±1.6% of C was mineralized after biochar addition of 1.5 g kg-1. In the SOM-labelled soil, the organic matter mineralized more slowly with the increasing doses of biochar. Biochar addition at 7.7 g kg-1 reduced SOM mineralization from 6.6 to 6.3%, during the experimental period. The addition of 15.5 g kg-1 of biochar reduced the mineralized SOM to 5.7%. There is no evidence of increased degradation of either litter or SOM due to biochar addition; consequently, there is no evidence of decreased stability of SOM.

Soil fertility and upland rice yield after biochar application in the Cerrado

The objective of this work was to evaluate the effect of biochar made from Eucalyptus on soil fertility, and on the yield and development of upland rice. The experiment was performed during two years in a randomized block design with four replicates, in a sandy loam Dystric Plinthosol. Four doses of NPK 05-25-15, annually distributed in stripes (0, 100, 200 and 300 kg ha-1), and four doses of biochar (0, 8, 16 and 32 Mg ha-1), applied once in the first year - alone or with NPK - were evaluated. In the first year, biochar positively affected soil fertility [total organic carbon (TOC), Ca, P, Al, H+Al, and pH], at 0-10 cm soil depth, and it was the only factor with significant effect on yield. In the second year, the effect of biochar diminished or was overcome by the fertilizer. TOC moved down in the soil profile to the 0-20 cm depth, influencing K availability in this layer. In the second year, there was a significant interaction between biochar and the fertilizer on plant growth and biomass dry matter accumulation.

Soil organic matter in fire-affected pastures and in an Araucaria forest in South-Brazilian Leptosols

The objective of this work was to evaluate the distribution pattern and composition of soil organic matter (SOM) and its physical pools of Leptosols periodically affected by fire over the last 100 years in South Brazil. Soil samples at 0-5, 5-10, and 10-15 cm depths were collected from the following environments: native pasture without burning in the last year and grazed with 0.5 livestock per hectare per year (1NB); native pasture without burning in the last 23 years and grazed with 2.0 livestock per hectare per year (23NB); and an Araucaria forest (AF). Physical fractionation was performed with the 0-5 and 5-10 cm soil layers. Soil C and N stocks were determined in the three depths and in the physical pools, and organic matter was characterized by infrared spectroscopy and thermogravimetry. The largest C stocks in all depths and physical pools were found under the AF. The 23NB environment showed the lowest soil C and N stocks at the 5-15 cm depth, which was related to the end of burning and to the higher grazing intensity. The SOM of the occluded light fraction showed a greater chemical recalcitrance in 1NB than in 23NB. Annual pasture burning does not affect soil C stocks up to 15 cm of depth.

Biochar and soil nitrous oxide emissions

The objective of this work was to evaluate the effect of biochar application on soil nitrous oxide emissions. The experiment was carried out in pots under greenhouse conditions. Four levels of ground commercial charcoal of 2 mm (biochar) were evaluated in a sandy Albaqualf (90% of sand): 0, 3, 6, and 9 Mg ha-1. All treatments received 100 kg ha-1 of N as urea. A cubic effect of biochar levels was observed on the N2O emissions. Biochar doses above 5 Mg ha-1 started to mitigate the emissions in the evaluated soil. However, lower doses promote the emissions.

CR1Dmod: A Matlab program to model 1D complex resistivity effects in electrical and electromagnetic surveys

We have constructed a forward modelling code in Matlab, capable of handling several commonly used electrical and electromagnetic methods in a 1D environment. We review the implemented electromagnetic field equations for grounded wires, frequency and transient soundings and present new solutions in the case of a non-magnetic first layer. The CR1Dmod code evaluates the Hankel transforms occurring in the field equations using either the Fast Hankel Transform based on digital filter theory, or a numerical integration scheme applied between the zeros of the Bessel function. A graphical user interface allows easy construction of 1D models and control of the parameters. Modelling results are in agreement with other authors, but the time of computation is less efficient than other available codes. Nevertheless, the CR1Dmod routine handles complex resistivities and offers solutions based on the full EM-equations as well as the quasi-static approximation. Thus, modelling of effects based on changes in the magnetic permeability and the permittivity is also possible.

Effect of conservation tillage and peat application on weed infestation on a clay soil

Selostus: Kynnöstä luopumisen ja turvelisäyksen vaikutus savimaan rikkakasvillisuuteen kevätviljakasvustossa

Fusarium wilt incidence and common bean yield according to the preceding crop and the soil tillage system

The objective of this work was to evaluate the effects of preceding crops and tillage systems on the incidence of Fusarium wilt (Fusarium oxysporum f. sp. phaseoli) and common bean (Phaseolus vulgaris) yield. The cultivar BRS Valente was cultivated under center‑pivot irrigation in the winter seasons of 2003, 2004 and 2005, after several preceding crops established in the summer seasons. Preceding crops included the legumes Cajanus cajan (pigeon pea), Stylosanthes guianensis, and Crotalaria spectabilis; the grasses Pennisetum glaucum (millet), Sorghum bicolor (forage sorghum), Panicum maximum, and Urochloa brizantha; and a consortium of maize (Zea mays) and U. brizantha (Santa Fé system). Experiments followed a strip‑plot design, with four replicates. Fusarium wilt incidence was higher in the no‑tillage system. Higher disease incidences corresponded to lower bean yields in 2003 and 2004. Previous summer cropping with U. brizantha, U. brizantha + maize consortium, and millet showed the lowest disease incidence. Therefore, the choice of preceding crops must be taken into account for managing Fusarium wilt on irrigated common bean crops in the Brazilian Cerrado.

Effects of forwarder tyre pressure on rut formation and soil compaction

Abstract

Intra-specific variation in cell wall constituents of needle age classes of Pinus sylvestris in relation to soil fertility status in Southwest England

Abstract

Ammonium and nitrate in soil and upland rice yield as affected by cover crops and their desiccation time

The objective of this work was to evaluate the effect of cover crops and their desiccation times on upland rice yield and on the levels of nitrate and ammonium in a no-tillage soil. The experiment was carried out in a randomized blocks, with split plots and three replicates. Cover crops (plots) were sowed in the off-season (March 2009). In November 2009, at 30, 20, 10 and 0 days before rice sowing (split plots), herbicide was applied on the cover crops (fallow, Panicum maximum, Urochloa ruziziensis, U. brizantha and millet). Straw and soil were sampled (0 - 10 cm) at the sowing day, and after 7, 14, 21, 28 and 35 days. Straws from millet and fallow were degraded more rapidly and provided the lowest level of nitrate in the soil. Urochloa ruziziensis, U. brizantha and P. maximum produced higher amounts of dry matter, and provided the highest levels of nitrate in the soil. Millet provides the lowest nitrate/ammonium ratio and the highest upland rice yield. Desiccations carried out at 30 and 20 days before sowing had the largest levels of nitrate in the soil at the sowing date. Nitrogen content and forms in the soil are affected by cover crops and their desiccation times.

Chemical attributes of a Hapludox soil after nine years of pig slurry application

The objective of this study was to evaluate the pig slurry application effects on chemical attributes of a Hapludox soil managed under no-tillage system. Treatments consisted of 50, 100 and 200 m³ ha-1 per year of pig slurry application, and a control with replacement of P and K exported through harvested grains. Attributes related to soil chemical reaction, exchange complex, and nutrient contents were determined in soil samples collected in the ninth year of experimentation from 0 - 0.025, 0.025 - 0.05, 0.05 - 0.10, 0.10 - 0.20, 0.20 - 0.40 and 0.40 - 0.60 m soil depths. The continuous application of high doses of pig slurry on the Oxisol surface under no-tillage acidifies the soil and increases Al, P, Cu, and Zn contents down to 0.2-m depth, and K levels down to 0.6-m depth.

Soil nitrate N as influenced by annually undersown cover crops in spring cereals

Selostus: Aluskasvien toistuvan käytön vaikutus maan nitraattityppeen viljan viljelyssä