Purpose The aim of the present study was to investigate structure alterations of a sandy-clay soil upon addition of different amounts of biochar (f bc ). Materials and methods All the f bc samples were analyzed by high energy moisture characteristic (HEMC) technique and 1 H nuclear magnetic resonance (NMR) relaxometry. HEMC was applied in order to evaluate aggregate stability of biocharamended soil samples. 1 H NMR relaxometry experiments were conducted for the evaluation of the pore distributions through the investigation of water dynamics of the same samples.Results and discussion The HEMC technique revealed improvement in aggregate stability through measurements of the amount of drainable pores and the stability ratio. The latter increased as the amount of biochar was raised up. The 1 H NMR relaxometry revealed a unimodal T 1 distribution for both the sole sandy-clay soil and the biochar. Conversely, a bimodal T 1 distribution was acquired for all the different f bc samples. Conclusions Improvement in aggregate stability was obtained as biochar was progressively added to the sandy-clay soil. A dual mechanism of water retention has been hypothesized. In particular, intra-aggregate porosity was indicated as the main responsible for molecular water diffusion when f bc comprised between 0 and 0.33. Conversely, inter-aggregate porosity resulted predominant, through swelling processes, when f bc overcame 0.33.
Forest and pasture soils should have differing properties due, for example, to differing root characteristics or livestock trampling rates, but contradictory results have been reported in the literature. The surface soil physical and hydraulic properties of five forest and pasture sites were determined in a Sicilian watershed. In general, forest soils had a significantly lower bulk density, p^ (by 17-35%), and a higher field saturated hydraulic conductivity, Kf( by a factor of 3.4-11.5), than pasture soils. Differences between the water retention characteristics of Forest and pasture soils were low when high levels of organic matter, OM (>7.1%), were detected for both land uses. The mean Kf^ varied with the amount of large pores (i.e., larger than 596 or 298 \im) in the soil. The mean of A";^ also increased with increasing OM content and decreased with an increase in p^ (coefficient of determination 0.69-0.74). According to existing guidelines for evaluating soil physical quality, a good or relatively good quality forest soil was a common result. At three sites, a worse pasture soil physical quality was detected than that of the forest.In conclusion, changing land use from pasture to forest should have a favorable impact on hydrologie processes in the sampled watershed due to the better physical quality of forest soils. The order of magnitude of the mean Kf^ was predictable using laboratory data. The applicability of the existing guidelines to assess soil physical quality was indirectly supported in this investigation because a better quality was expected for the forest soils than the pasture soils.
Microirrigation plants, if properly designed, allow water use efficiency to be optimized and quite high values of emission uniformity to be obtained in the field. It is known that disposing paired laterals, in which two distribution pipes extend in opposite directions from a common manifold, contribute to increasing water use efficiency. Recently, an analytical procedure has been proposed to optimally design paired drip laterals on uniform slopes under the assumption of neglect: (1) the variations of the emitters’ flow rate along the lateral, and (2) the local losses due to the emitters’ insertions. However, this procedure is not readily usable for every geometric and hydraulic characteristic of the lateral and slope fields because it requires solving a system of implicit equations. This study derives simple explicit relationships, reproducing the proposed approach, allowing derivation of the design variables that are required for the optimal design. Moreover, an easy method to determine the best position of the manifold associated to the optimal lateral length on uniform slopes is proposed, making evident a very moderate influence of the geometric and hydraulic characteristics of the lateral. The proposed procedure was successful compared with that derived by the analytical solution. Applications of the proposed relationships, considering different design parameters, are presented and discussed
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