Estimation of field capacity for aggregated soils using changes of the water retention curve under the effects of compaction

Abstract

Summary The objective of this study is to present a new method for field capacity estimations using the CPV function (changes in pore volume). The method requires water retention data of an aggregated soil before and after a compaction event. The CPV function estimates the threshold of equivalent pore diameter (D‐threshold) between structural and textural porosity using changes in the water retention curve. The D‐threshold corresponds to a water potential associated with field capacity according to the TFC concept (textural field capacity), which assumes that (i) the textural pores define the field capacity conditions and (ii) the D‐threshold and consequently the water potential at field capacity are constant parameters for each soil regardless of its compaction state. Published datasets for different aggregated soils subjected to different compaction processes and data from a lysimeter drainage experiment were used to evaluate the method. The analysis of the drainage experiment was supported by the BUDGETv.6.2 model, which was used to estimate the optimum value of the water content at field capacity (parameter of the model) using observed soil water contents and drainage rates during the drainage experiment (concept of inverse problem). The results for different soils subjected to compaction showed that the estimated water potentials by the CPV method follow the commonly accepted assumptions that govern field capacity conditions, justifying also the assumptions of the TFC concept. The field capacity conditions estimated by the model demonstrated an adequate correspondence to the results of the CPV method, indicating its ability to assess the field capacity conditions of the lysimeter soils.

Analysis of Water Retention Capacity for Select Forest Soils in Poland

“…The obtained results in the forms of empirical equations generally are in agreement with data presented in the literature [5,15,29]. However, it should be stressed that forecasting of the field capacity, commonly assumed at pF=2, which is a very important soil moisture status [6,32], the S pl fraction content was required.…”

“…Thus the pF curves are useful for calculating available water capacity (AWC) in the soil [5] and are the basis for determining irrigation rate [6,7]. Despite developing measurement methodology of pF curve [3], the sourcing of these characteristics remains labor-intensive.…”

Scheduling irrigation using an approach based on the van Genuchten model

“…The slope of the line tangent to the inflection point reflects soil physical quality, including relative field capacity (the proportion of soil VWC at FC over saturation), plant-available water capacity, air capacity, and macroporosity (Reynolds et al, 2009). The "textural" pores determine FC (Aschonitis et al, 2013). In the range between FC and PWP, soil water is barely draining but available for plant water uptake (Brady and Weil, 2008), even if it becomes increasingly difficult for plant roots to extract water from these smaller pores.…”

The concept of field capacity revisited: Defining intrinsic static and dynamic criteria for soil internal drainage dynamics

“…The FC concept remained ambiguous and subject to criticism since its inception, and long‐held views asserting that “ the hydraulics of water in soils at field capacity are not well understood ” [ Miller and McMurdie , ] have not changed much [ Nachabe , ; Twarakavi et al ., ; Aschonitis et al ., ]. Some of the criticism stems from the fact that FC “ is not truly an equilibrium water content but instead is that water content at which the soil water flux out of the rooting zone becomes negligible and no significant change in water content occurs with time ” [ Cassel and Nielsen , ].…”