Available_K             Available potassium (K) in soil
Available_P             Available phosphorus (P) in soil determined by
                        ascorbic acid blue colour method
DTPA_Micro              Available micronutrient cations in soil
Mineral_N               Mineral N i.e., summation of ammonium-N and
                        nitrate-N in soil
N_Boric                 Total, or Mineralizable Nitrogen using boric
                        acid for ammonia absorption
N_Sulphuric             Total Nitrogen (N) using sulphuric acid for
                        ammonia absorption
Std_Curve               Elemental concentration in solution from
                        absorbance or emission values
WBC                     Oxidizable organic carbon (C) or Walkley-Black
                        C in soil
df_Available_K          Example Data Frame for available potassium (K)
                        in soils
df_Available_P          Example Data Frame for available phosphorus (P)
                        in soils
df_DTPA_Micro           Example Data Frame for available micronutrient
                        cations in soils
df_Minearl_N            Example Data Frame for mineral nitrogen (N) in
                        soil
df_N_Boric              Example Data Frame for total nitrogen (N) and
                        available or mineralizable N in soil
df_N_Sulphuric          Example Data Frame for total nitrogen (N) in
                        soil
df_Std_Curve            Example Data Frame for element concentration
                        from standard curve
df_WBC                  Example Data Frame for oxidizable organic
                        carbon (C) or Walkley-Black C in soil
