Comparing physical quality of tilled and no-tilled soils in an almond orchard in southern Italy

Abstract

No-tillage (NT) is an alternative way of reducing costs and lessening the burden of working the land, but in essence it is a method of sustainable land use in dryland cropping systems. The physical quality of the soil is the fundamental factor that defines the sustainability of agro-ecosystems, and its evaluation can be obtained using both capacitive and dynamic indicators. The main objectives of this study were: i) to assess the physical quality of the soil in an almond orchard where long-term different soil tillage systems and weed control methods, such as NT with chemical control and surface tillage (ST), were used; and ii) to compare the indicators under consideration with the proposed reference values, using the information gathered to evaluate the effects of NT and ST. The following physical properties were determined: bulk density, air capacity, macroporosity, plant available water capacity, relative field capacity, Dexter's index, field saturated hydraulic conductivity, as well as the location (modal, median, and mean pore diameter) and shape (standard deviation, skewness, and kurtosis) parameters which corresponded to the equivalent pore size distribution functions. Our results showed that the physical soil indicators adopted were sufficiently sensitive to identify tillage-induced changes and then to quantify the physical quality of rigid to moderately expansive agricultural soils. After thirty years of NT, a set of capacitive indicators, along with measurements of hydraulic conductivity, used in conjunction with an optimal pore volume distribution and the water release curve, unanimously classified the quality of the studied soil as optimal or near optimal.

Temporal changes of soil physical quality under two residue management systems

“…It has been reported that PAWC and S‐index vary over time, and the relationship with soil bulk density adequately can explain such trends. In our study, the first relationship was always negative for all sampling date (S‐index decreases as BD increases), confirming what has been reported in literature (Castellini et al ., ). However, the relationship PAWC‐BD showed both positive and negative trends (Figure ).…”

“…Probably, the positive effects of OC on improving of soil structure were counterbalanced by the clayey matrix of soil that represents the most important factor for soil structural stability (Dexter, ). Our results suggest that when a set of soil physical quality indicators was chosen, the related results should be interpreted with caution, because it is rare for all the indicators to agree (Castellini et al ., ). Even though our study only considered two types of soil management practice, the results are consistent with those reported by Reynolds et al .…”

“…This interpretation is supported by the recent results of the research by Castellini et al . (), in which they compared the physical quality of tilled and untilled clay soil. The long‐term tilled soil had lower densities of small pores and relatively higher densities of large pores than either the untilled soil or than the optimal distribution proposed by Reynolds et al .…”

“…However, to date, the approach proposed by Reynolds et al . () has been applied in only a few cases (Castellini et al ., ; Iovino et al ., ) and further research is desirable.…”

Impact of biochar addition on the physical and hydraulic properties of a clay soil

“…These indicators were macroporosity (P mac = u s À u m ) (L 3 /L 3 ), air capacity (AC = u s À u FC ) (L 3 /L 3 ), plant available water capacity (PAWC = u FC À u PWP ) (L 3 /L 3 ) and relative field capacity (RFC = u FC /u s ), where u m , u FC , u PWP are the volumetric water content corresponding to h = À10, À100 and À15300 cm, respectively. Some reference values for these capacitive indicator as described in the literature were also considered, in order to evaluate whether the modifications induced by biochar addition led to an improvement or a worsening of the physical properties of the soil (Castellini et al, 2013). A brief review can be found in Reynolds et al (2009).…”