This question is connected to another one I asked some days ago: How to do a table with multiple multirows_.
The problem I have is that my text does not fit nicely in the \multirowcell and I haven't been able to find too much information to fix this issue.

This is the real table I'm working with so you can see what I mean. Thanks a lot for input.
% Doc. structure
\documentclass[11pt,a4paper]{report}
% Packages
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage[]{graphicx} % Loading graphicx in the preamble it's possible to import pdf images in the document
\usepackage{float}
\usepackage{multicol}
\usepackage[round]{natbib} % For citations
\newcommand{\textsubscript}[1]{$_{\text{#1}}$}
\newcommand{\textdegree}[1]{${^\circ}$}
\usepackage[nomarginpar]{geometry}
\usepackage{array, booktabs, tabularx, makecell, multirow}
\renewcommand{\tabularxcolumn}[1]{>{\raggedright\arraybackslash}m{#1}}
\renewcommand\cellalign{Xc}
\begin{document}
\vspace*{1\baselineskip}
\centering
\begin{tabularx}
\linewidth{ | *{3}{ >{\centering}m{2.8cm}|} X |}
\cline{2-4}
\multicolumn{1}{c|}{}
&
Soil required in lab (Sieved \textless 2mm &
Soil collected in the field &
Notes \\
\hline
\multirow{3}{*}
{Fresh sample} &
Incubations 60 g (105C dry conversion) x 2 &
Incubations about 200 g (moist) x 2 &
\multirowcell{3}{Big losses during sieving. From here:
\begin{description}
\item[-] Long-term incubation
\item[-] Short-term incubation. From soil solution: DOC, DMN, DMP
\item[-] Water retention curve \& equivalent 105
\item[-] pH
\end{description}} \\
\cline{2-3}
&
Water retention curve $\sim$\,150\,g &
Water retention curve $\sim$\,200\,g &
\\
\hline
Frozen sample &
$\sim$\,60\,g (105C dry conversion) &
$\sim$\,150\,g fresh soil &
From here, mineral N and P. To compare results of saturation paste with soil solution extract at day 0. \\
\hline
Dry sample &
$\sim$\,60\,g &
$\sim$\,150\,g fresh soil &
From here:
\begin{description}
\item[-] Fe, Al
\item[-] Organic N, P
\item[-] Organic C
\item[-] Bulk soil 14C
\item[-] Carbonates
\item[-] Clay
\end{description}\\
\hline
\end{tabularx}
\end{document}

multirowyou could also use nested tabulars: http://tex.stackexchange.com/a/188523/5049 – cgnieder Jul 22 '14 at 07:45