Soil¶
Purpose and Perspective¶
The purpose of the Soil sector is to determine soil nutrients balances and their long-term impact on soil organic matter. We consider flows of the three major soil macro-nutrients (Nitrogen, Phosphorous, and Potassium) as they relate to agricultural activities. More specifically we consider as inflows nutrients addition through fertilization (both mineral fertilizer and manure), biological fixation (symbiotic, non-symbiotic, chemoautotrophic, and from scattered trees), and deposition. We consider as outflows nutrient use (uptake from crops and crops residuals removed) and losses (leaching and gaseous losses). Finally, the gap emerging between nutrients inflows and outflows is drawn from soil organic matter. This representation is fundamentally based on FAO’s nutrients balance work [1].
Model Structure and Major Assumptions¶
Nutrient inflows include fertilization, biological fixation, deposition, and mineral weathering [2]
Nutrient outflows include nutrient use and losses [3]
Nutrient imbalance is drawn from soil organic matter [4]
Mineralization rate estimated based on Del Pino Machado (2005) [5]
Soil management training unit cost estimated based on Quizon (2001) [6]
Exogenous Input Variables¶
Fertilizer consumption[nutrient] - Units: Ton/Year
Nutrient uptake proportion[crop,nutrient] - Units: Dmnl
US fertilizer price per ton of nutrient[nutrient] - Units: Usd/Ton
Initialization Variables¶
Initial soil organic carbon density
Modeling Details¶
The subscript [nutrient] is used to separately keep track of nutrients flows and balance for the three major nutrients: nitrogen, phosphorous, and potassium. By expansion of such subscripts, further nutrients can be included the analysis, where necessary.
Footnotes and References¶
[1] Roy, R.N., Misra, R.V., Lesschen, J.P. & Smaling, E.M. (2003). Assessment of soil nutrient balance. Rome: FAO Land and Water Development Division, Food and Agriculture Organization of the United Nations.
[2] Andersson, F., Braekke, F.H. & Hallbäcken, L. (Eds.) (1998). Nutrition and growth of Norway spruce forests in a Nordic climatic and deposition gradient. Copenhagen: TemaNord, Nordic Council of Ministers.
Kirkby, C.A., Kirkegaard, J.A., Richardson, A.E., Wade, L.J., Blanchard, C., & Batten, G. (2011). Stable soil organic matter: A comparison of C:N:P:S ratios in Australian and otherworld soils. Geoderma 163: 197–208.
Roy, R.N., Misra, R.V., Lesschen, J.P. & Smaling, E.M. (2003). Assessment of soil nutrient balance. Rome: FAO Land and Water Development Division, Food and Agriculture Organization of the United Nations.
[3] Roy, R.N., Misra, R.V., Lesschen, J.P. & Smaling, E.M. (2003). Assessment of soil nutrient balance. Rome: FAO Land and Water Development Division, Food and Agriculture Organization of the United Nations.
[4] Bot, A., Benites, J. (2005). The importance of soil organic matter Key to drought-resistant soil and sustained food and production. FAO Land and Plant Nutrition Management Service. Rome: Food and Agriculture Organization of the United Nations.
[5] Del Pino Machado, A.S. (2005). Estimating nitrogen mineralization potential of soils and the effect of water and temperature and crop residues on nitrogen net mineralization. Gottingen: Cuvillier Verlag.
[6] Quizon, J., Feder, G., & Murgai, R. (2001). Fiscal Sustainability of Agricultural Extension: The Case of the Farmer Field School Approach. Washington, DC: World Bank.
