The purpose of Gypsy is to help farmers make decisions on what rates of gypsum to apply to sodic soils. Crop growth and yield are badly affected by soil sodicity in considerable areas. Adding gypsum, which is a relatively soluble source of calcium, can often reduce soil sodicity. The optimum amount to add depends on several soil properties, as well as climate, irrigation water amount and quality, costs and prices. Gypsy can be used to estimate the effect of gypsum on the exchangeable sodium under any crop, and a cost-benefit calculation can be made for sugarcane. The program is designed to run with a minimum of inputs and therefore involves various assumptions, so it is intended as an approximate guide only.
The profile-based analysis of this new online version of Gypsy performs the same analysis offered by the original Gypsy software.
The field-based analysis of this new online version of Gypsy performs variable-rate calculation of gypsum requirement based on a boundary file of a field. Upload an ESRI shapefile to allow the delineation of field boundaries. Note that a shapefile consists of different files with extensions .shp, .dbf, .shx, .prj. Select all the relevant files then click upload. Select the desired soil depths of calculation from the drop-down menu. Click calculate.
The zonal-based analysis of this new online version of Gypsy performs gypsum recommendation based on zonal data. Key in the budget available for the field in question.Upload a .csv file with the following headings in this order: ZoneName, Area (ha), UpperDepth (cm), LowerDepth (cm), EC (dS/m), CEC (cmol(+)/kg), ExNa (cmol(+)/kg), ESP (%), Cl (mg/kg), BD (t/m3), F factor. Please use an F factor of 2 for surface soil and an F factor of 1 for subsoil rows as per Green et al. (2023). The gypsum application recommended for each zone will be capped at 10 t/ha and is based on maximizing net-benefit of the whole field.
Electrical conductivity (EC) is used to measure the salinity of soil extracts or water. Conversion between the EC units (μS/cm, mS/cm, dS/m) and the concentration units (mg/L, ppm, grains/gallon) are approximate.
Soil salinity is determined by measuring the EC of a 1:5 soil water extract (EC1:5) or a saturated paste extract (ECs.e.). It is possible to convert between the two if the soil texture is known.
Units: me %, meq/100g and cmol(+)/kg are numerically equal
Achieving a desired electrical conductivity (EC) in a mix
Concentration of any component (e.g. residual alkali) in the mix
SAR of mix
Proportion of water to pass through dissolvenator
SAR of the mix
Gypsy can be run in several ways. It can be run with one soil analysis (‘Profile-based’ tab), or using a shape file for a paddock (‘Field-based’ tab), or with a file for a paddock with different zones (each with an area and its respective soil analysis), which optimises gypsum applications for each zone across the paddock for a given budget (‘Zonal-based’ tab). Within each of these three running modes, the crop is chosen, either sugarcane or wheat.
For sugarcane, Gypsy estimates the influence of a gypsum addition on sugarcane yield and cash flow on neutral-alkaline soils in Australia, using known relationships between yield and sodicity, and the effect of gypsum on sodicity (Green et al., 2023, Nelson et al., 2000). The inputs are cation exchange capacity (CEC) and exchangeable sodium percentage (ESP) for the 0-25 cm and 25-50 cm depth layers, cost and quality of the gypsum, price of cane, and a discount rate. The output is a cash flow analysis, with a graph showing the net benefit against different gypsum rates. Gypsy is designed for Australian sugarcane growers and their advisors, to be used together with the manual “Diagnosis and Management of Sodic Soils under Sugarcane” (Nelson et al., 2001), the “Field Guide for Diagnosis of Sodic Soils in the Sugar Industry” (Nelson, 2000), and local experience. For field-based analysis, currently, only areas within the GRDC northern grain-cropping region (NGR) will return a result because ESP maps are available only for that region (Lai et al., 2020). This means that it will not work for most sugar-growing regions apart from a small area near Sarina, Queensland. A next step might be to produce ESP maps for Australia, or at least for the sugar and grains cropping regions, to enable its wider application.
The wheat option is not yet parameterised and is for illustration only. A meta-analysis on the effects of sodicity amelioration on yield is being conducted. It will hopefully inform the yield and economic analysis for wheat and be incorporated into Gypsy in the future.There are also tabs for calculations of sodicity and salinity-related properties of soil and water. As irrigation water quality is critical to managing sodic soils, Gypsy can also be used to calculate how irrigation water quality can be modified using a dissolvenator or by mixing water from different sources (conjunctive use). Gypsy can also be used to calculate CEC and ESP from exchangeable cation values, to convert between different units for electrical conductivity (EC), and to estimate changes in ESP when lime is added to acid sodic topsoils.
This online version of Gypsy Program (Gypsy Calculator) was created by Chloe Lai, funded by the CRC for High Performance Soils, in consultation with Peter Larsen, Gus Manatsa and Rob Milla. It is based on the Gypsy Program. The underlying calculations are described by Nelson et al. (2000).
Green, H., Larsen, P., Koci, J., Edwards, W. and Nelson, P.N., 2023. Long-term effects of gypsum on the chemistry of sodic soils. Soil and Tillage Research, 233, p.105780. doi.org/10.1016/j.still.2023.105780.
Lai, Y.R., Orton, T. G., Pringle, M. J., Menzies, N. W., & Dang, Y. P. 2020. Increment averaged kriging: a comparison with depth-harmonized mapping of soil exchangeable sodium percentage in a cropping region of eastern Australia. Geoderma, 363, 114151. doi:10.1016/j.geoderma.2019.114151.