Crop Rotation in sustainable farming

Problem definition

Crop rotation is based on growing a series of different types of crops in the same area in sequential seasons. The planned rotation may vary from a growing season to a few years or even longer periods. It is one of the most effective agricultural control strategies that is used in preventing the loss of soil fertility. It also helps in reducing soil erosion and increases crop yield. Planning an effective crop rotation requires weighing fixed and fluctuating production circumstances: market, farm size, labor supply, climate, soil type, growing practices, etc.

In this simulation I will try to find parameters which have impact on the whole process of crop rotation with goal to find model providing desired outputs (these were slightly changed from concept) - crop yields, greenhouse gas emissions (N2O, CO2, NH4), soil fertility (nitrogen levels).

I will focus on four crop rotation strategies with three different crops - corn, soybean, wheat:

CCC (continuous corn) - only corn will be farmed for the whole observed time period (40 years)

CS (corn-soybean) - rotation of corn and soybean will be used in year cycles for the whole observed time period (40 years), first year corn, second year soybean, repeat..

SSS (continuous soybean) - only soybean will be farmed for the whole observed time period (40 years)

CSW (corn-soybean-wheat) - rotation of corn, soybean and wheat will be used in year cycles for the whole observed time period (40 years), first year corn, second year soybean, third year wheat, repeat..

Goal of this simulation is to observe dynamic changes with yields, greenhouse gas emissions and soil nitrogen levels, while changing different crop rotation strategies.

Method

Vensim modelling approach was selected due to dynamic behavior of the simulated system.

Model

Variables

Number of rotated crops <1,3> Corn production Corn quantity*PULSE TRAIN(0, 1 , Number of rotated crops ,40) Soybean production Soybean quantity*PULSE TRAIN(IF THEN ELSE(Number of rotated crops=1, 0 , 1 ), 1 , Number of rotated crops , 40 ) Wheat production Wheat quantity*PULSE TRAIN(IF THEN ELSE(Number of rotated crops=1, 0 , 2 ), 1 , Number of rotated crops , 40 ) Corn quantity <0,100> Soybean quantity <0,40> Wheat quantity <0,80> increase of N2O emissions increase of CO2 emissions increase of CH4 emissions Cumulative N2O emissions Cumulative CO2 emissions Cumulative CH4 emissions Corn N2O emission coef Soybean N2O emission coef Wheat N2O emission coef Corn CO2 emission coef Soybean CO2 emission coef Wheat CO2 emission coef Corn CH4 emission coef Soybean CH4 emission coef Wheat CH4 emission coef Inorganic fertilizer Soil nitrogen increase of soil N decrease of soil N Soil nitrogen level Temperature Precipitation Pests Tillage Natural disasters increase of C yield increase of S yield increase of W yield Corn yield Soybean yield Wheat yield Total yield = Corn yield + Soybean yield + Wheat yield