During the seasons 2003/04, 2004/05 and 2005/06, a study was made of the evolution of runoff as well as soil and available P and K losses in the sediment carried away in a conventional till system-that most used at the present time-and in a no till system with added pruning remains in an olive grove of the picual variety located in Torredonjimeno (Jaén, Spain). A group of microplots for sediment collection in a randomized complete block design was established. The samples were collected in the field after each storm. In the study period, a total of 21 storms were recorded, with a precipitation of 450 mm in 2003/04, 179 mm in 2004/05 and 388 mm in 2005/06. The erosivity of the rainfall was characterized and the cover percentage in the plots throughout the time was determined. The establishment of pruning remains reduced soil loss with respect to conventional tillage (CT) in the 3 years (72%). Likewise, the available P loss greatly declined in the study (46.4%) under conservation agriculture. The reduction in available K loss (72.4%) was much greater than that of available P. The close relationship between both variables and sediment production also stands out. Runoff was the parameter on which the pruning remains had the least influence with only an 11% average reduction.

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SUMMARYThe arrival on the market of various types of mulchers and chippers has boosted the use of pruning residues as plant cover among olive growers. In order to increase knowledge regarding the decomposition of these types of residues and their effect on soil fertility, an experiment was performed using different doses and sizes of pruning residues applied on the areas between the lines of olive trees in an organic olive grove.Experiments were conducted over a period of two growing seasons (2009/10 and 2010/11). Treatments consisted of fine (⩽8 cm in diameter) and thick (>8 cm in diameter) pruning residues in the amounts indicated, I=2·65 kg/m2 fine; II=2·65 kg/m2 fine+1·12 kg/m2 thick; III=5·30 kg/m2 fine; IV=5·30 kg/m2 fine+2·24 kg/m2 thick; and a control without residues.As regards the loss of biomass and nutrients during the decomposition of residues, two phases were observed. First, soluble compounds were degraded during a rapid initial phase, while in a second and slower phase, lignocellulosic compounds were decomposed. As a result, the pattern over time of nitrogen (N), phosphorus (P) and potassium (K) release fitted a double exponential model better, regardless of the treatment considered, registering in most cases determination coefficients close to one.The favourable results observed in terms of augmentation in N, P and K soil content following the application of pruning residues confirmed a greater improvement in soil fertility than the soil covered by spontaneous weeds, which is the option most frequently adopted by organic olive growers. The initial amount of pruning residues has influenced the amount of soil nutrients. Considering the entirety of the soil profile (0–40 cm) and the content of these elements in the soil, treatment III, which contained the largest amount of fine residues, was the most efficient in terms of improving soil fertility, recording increases in the concentration of N, P and K of 1805·4, 53·1 and 598·7 kg/ha, respectively. The most unfavourable results were recorded by treatment I, with increases of 480·9 kg/ha in the case of N and a decrease in P content with regard to the control sample. Treatment II increased K (recording 215·2 kg/ha) which was the least in comparison to the control sample.

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<p class="western" align="JUSTIFY"><span lang="en-GB">The seminatural prairie of the Raña of Cañamero (Spain) is a degraded and unproductive agrosystem with acid and stony soils, and low coverage of xerophytic grasses. In a project about secondary reconversion of the raña-prairie to a more productive cropland, an experimental field (EF) was established to assess the effect on plot-productivity of the interaction between correction of soil pH (liming) with three cropping systems: a no-tilled and annually fertilized and improved prairies, and a conventionally-tilled forage crop. The EF model of management was designed as plant-conservative, because no herbicide was applied after seeding to preserve the post-emergence of wild herbs and the natural grass diversity of the prairie. Between 2008 and 2012, we analysed the effect of managing factors (initial conventional-tillage, fertilization, liming and cropping) and agricultural predictors (pH, C:N ratio, soil bulk density and herbaceous biomass) on the alpha(α)-diversity of one of the major group of soil animals, the oribatids. In relation to the raña-prairie, all EF-plots improved their soil bulk density (ρ_s) and herbaceous biomass (t/ha), and enhanced desirable α-diversity values (richness, abundance and community equity). We conclude that the plant-conservative model: i) do not affect statistically the species richness of the prairie; ii) the desirable α-diversity responses are negatively correlated with soil bulk density and positively with herbaceous biomass, and iii) the low input or minimum intervention model, of an initial and conventional till and annual fertilisation, is the threshold and optimal model of agricultural management to improving oribatids diversity of the raña-soil.</span></p>