This section may be divided by subheadings. It should provide a concise and precise description of the experimental results, their interpretation, as well as the experimental conclusions that can be drawn.
3.2. Descriptive Analysis
The result of the descriptive analysis (
Table 1) revealed a significant variability in the total range of all the variables chosen for this study.
This fact can be explained by the increase in prices of inputs used in the production of corn and soybeans from 2018 to 2022. The 59% appreciation of the dollar is related to the rise in prices of fertilizers, soil amendments, and agricultural pesticides during the studied period [38-42], as the dollar is the currency used in international transactions, including the trade of agricultural inputs that need to be imported by farmers.
In addition to these factors, uncertainties caused by the Covid-19 pandemic have led to imbalances between supply and demand of inputs in the global market, which have influenced significant fluctuations in prices of fertilizers, herbicides, fuel, and other inputs analyzed in this study [
43]. The uncertainties stemming from the pandemic have affected all sectors of the agribusiness, from production to distribution and marketing, resulting in negative economic impacts across all segments, particularly in input costs [4, 44].
In contrast, the increase in the value of the dollar can also stimulate the exports of corn and soybeans, thereby reducing the domestic supply and further raising prices [
45]. Given this scenario, it is crucial for the agricultural sector to be attentive to ex-change rate fluctuations and seek alternatives to mitigate the impact of the rising dol-lar on production costs.
The lowest variances and standard deviations were found for the collected prices of diesel fuel, dollar exchange rate, soybean seed, and corn seed. This indicates that the values of these inputs and the exchange rate did not deviate significantly from the mean during the study period.
The coefficient of variation results indicated that the prices of the following variables: diesel fuel, glyphosate herbicide, dolomitic limestone corrective, NPK 05-25-25 fertilizer, corn bushel, soybean bushel, soybean seed, potassium chloride fertilizer, and urea fertilizer exhibited a high dispersion. On the other hand, the prices of tiamethoxam lambda-cyhalothrin insecticide, dollar exchange rate, corn seed, and casual labor had a moderate dispersion, while the prices of trifloxystrobin tebuconazole fungicide and tractor operator labor were classified as having low dispersion.
The highest coefficient of variation was found for the glyphosate herbicide. The literature suggests that in addition to the external factors, internal factors such as market demand, production costs, distribution, and sales of each company, as well as government intervention (such as taxation on imported products), influence the costs and consequently the price formation of this herbicide [
46].
The lowest coefficient of variation was found in the price of the variable "tractor operator labor." Although it showed low dispersion over the study period, expenses related to tractor operators' salary payments have shown great relevance in the total production costs of corn and soybeans [47-48].
No variable exhibited symmetry in the analyzed prices during the period from 2018 to 2022. Positive skewness distributions were found for: diesel oil, fungicide tri-floxystrobin tebuconazole, herbicide glyphosate, insecticide thiamethoxam lambda-cyhalothrin, dolomitic limestone corrective, fertilizer NPK 05-25-25, soybean bag price, corn bag price, soybean seed, tractor operator labor, daily laborer labor, potassium chloride fertilizer, and urea fertilizer. This means that the prices of these inputs remained above the average for a significant part of the analyzed period, which can be explained by the factors discussed earlier. The US dollar and corn seed were the only variables in which prices exhibited negative skewness distributions, meaning that they remained below the average for a significant part of the analyzed period. Despite reaching high values at times, the dollar remained below the average in recent years due to a combination of factors, including a decline in the performance of the US economy, which has not remained as strong due to global instabilities and political tensions [
49]. Regarding corn seed, the study conducted by Seidler et al. (2022) [
50] suggests that in addition to the exchange rate, the prices of this commodity in São Paulo are influenced by the prices in Sorriso - MT and in Paraguay, as they are the main national production areas and the origin of most of the corn imported by Brazil.
For the analysis of kurtosis, it was evident that the prices of corn seed exhibited a platykurtic distribution, meaning that the values were more concentrated around the mean. The price of corn seed in São Paulo increased by 120% from 2018 (USD 1,827.1) to 2022 (USD 4,028.54) [
51]. This significant variability can be explained by changes in the commodities market and currency fluctuations that affect corn costs [52-54]
Regarding the price of the herbicide glyphosate and the price of diesel fuel, the mesokurtic distribution found for these inputs (moderate concentration of values around the mean) may be related to economic and environmental factors related to production, supply, and demand of these products [46, 55]. The remaining variables exhibited a leptokurtic distribution (relatively low concentration of values around the mean). The leptokurtic distribution in the prices of the agricultural inputs studied may have been influenced by the pandemic [24, 43], variations in agricultural productivity [
39], supply and demand [
40], and the price of the dollar [38, 41-42].
Understanding the factors that influence the costs of inputs to produce corn and soybeans, as well as the behavior of price variability, is crucial for producers to make informed decisions and better plan their crops. By doing so, it becomes possible to ensure the sustainability of agricultural production and maintain competitive-ness in the global market.
3.3. Financial Analysis of Corn and Soybeans
The data related to prices, dosage of inputs used in soybean and corn cultivation, production costs, the percentage that each variable represents, and net profit were collected (
Table 2). The variables that had the highest percentage of contribution to the total production cost of these crops were NPK 05-25-25 fertilizer (45.9% in corn production and 56.5% in soybean production), soybean seeds (15.7% in soybean production), corn seeds (10.5% in corn production), potassium chloride fertilizer (9.6% in corn pro-duction), and urea (9.2% in soybean production).
The levels of certainty regarding the average production cost per hectare of corn associated with the analyzed variables were calculated using MCS and are presented in the cumulative frequency graph (
Figure 1).
The simulation results presented in
Figure 1 show that the range between USD 260.00 and USD 420.00 contains the average production costs of soybean per hectare paid in the state of São Paulo, with a level of certainty of 86.4% for an average of USD 340.20 and a standard deviation of USD 53.55, considering the period from 2018 to 2022.
These results provide information based on the analyzed historical prices. Thus, the analysis conducted can help minimize uncertainties regarding soybean production costs for the state and assist in making informed decisions regarding input purchases through this forecast.
The values obtained in this study are supported by the data collected by Conab (2022) [
58] for the state of São Paulo, specifically the city of Assis, one of the main corn-producing municipalities in the state. The values provided by Conab are in Brazilian Reais and have been converted to US Dollars using the average commercial ex-change rate (R
$/USD) for each year. The data used in this analysis were obtained from IPEAdata, available from the authors upon request). For comparison purposes, the average calculation was performed considering only the costs of operating expenses, excluding other costs such as storage, charges, among others. The average production cost of soybeans was found to be USD 417.77 during the period from 2019 to 2021.
The levels of certainty of the average production cost per hectare of corn associated with the analyzed variables were calculated using SMC and are presented in the cumulative frequency graph (
Figure 2).
The simulation results show that the range between USD600.00 and USD1150.00 contains the average production costs of corn per hectare in the state of São Paulo, with a level of certainty of 84.7% for an average of USD870.80 and a standard deviation of USD192.40, considering the period from 2018 to 2022.
The monitoring data from Conab (2022) [
59] regarding the production costs of the second corn crop for the years 2019 and 2020 show an average production cost of USD421.26, represented by the city of Assis. On the other hand, Ventura et al. (2020) [
20] indicate costs in other productive states in Brazil that corroborate with the results, ranging from USD613.00 to USD653.00 in the 2018/19 and 2019/20 crops (using trans-genic seeds).
The authors of this study observed that the production costs in each municipality/state were influenced by differences in productivity. Areas with higher productivity had lower production costs compared to smaller areas [
19]. In addition to productivity, other factors contribute to the observed differences in corn production costs in different regions, such as climate [
60], prices of inputs [
61], and employed technology [62-63].
Considering the variables in this study, the most significant production costs for corn and soybeans (fertilizers and soil amendments) account for 68.7% and 61.5% respectively. Equally important, the costs of agricultural inputs (herbicides, insecticides, and fungicides) amount to 15% and 18.4% for both crops.
An alternative to reduce these costs would be the use of Variable Rate Technology (VRT) (application of soil amendments and fertilizers according to each point analyzed by grid or management zone) [
11]. Supporting the above statement, Baio et al. (2018) [
64] reported that this technique is employed in precision agriculture for the application of inputs and agricultural pesticides, which allows for the rationalization of these products. The authors affirmed that the use of VRT system proved to be advantageous in agricultural production.
Another hypothesis to reduce consumption and, consequently, the cost of chemical fertilizers in Brazil would be the use of organ mineral fertilizers (combinations of organic sources). Corroborating this, Freitas et al. (2021) [
65] stated that this type of fertilizer emerges as an alternative for nutrient supply in corn cultivation and contributes to a reduced dependence on imported mineral fertilizers, in addition to being proven to increase productivity.
Reinforcing the statement, a case study in soybean cultivation in Brazil demonstrated that organ mineral fertilizers proved to be effective, achieving a productivity of 3,648.96 kg/ha, and could be an alternative to traditional mineral fertilization [
66]. In general, international evidence of the efficacy of using organ mineral fertilizers in agricultural production is emphasized by Marchuk et al. (2023) [
67] and Smith et al. (2020) [
68].
Another hypothesis to reduce the total cost regarding the use of agricultural pesticides, which has shown significant growth, is the use of biological products. Van Lenteren et al. (2018) [
69] reported that the use of biological control is growing at a rate of 10% to 20% per year worldwide. Spark (2021) [
70] stated that the use of biological products in Brazil covered approximately 33 million hectares, with the largest areas being soybean (20 million ha) followed by corn (9.8 million ha).
To conclude, the gross revenue of corn is 9.1% lower than that of soybeans. This is due to several factors, such as the higher production cost per hectare for corn (18.8%) compared to soybeans, and a 7.6% lower price per 60kg sack, as mentioned above. However, the average prices (paid to farmers during the studied period) for corn at USD11.3 and soybeans at USD22.6 are close to the price levels of September 2020, indicating stability in prices.
3.5. Monte Carlo Simulation – Predictor
For the next 24 months, it was evidenced that the urea fertilizer (
Figure 3A) shows a trend of stability in its price, while the NPK 05-25-25 fertilizer shows a downward trend (
Figure 3B).
In this sense, it is possible to infer that the production cost of soybean planting is likely to decrease for the next two harvests, as the price of the NPK 05-25-25 fertilizer shows a strong correlation with the production cost of this crop. The stability in the price of urea for the next 24 months is due to the significant increase in the exchange rate in recent months, especially for the nitrogen component. It is important to note that the NPK 05-25-25 fertilizer utilizes 5% of this component in its formulation.
Among the models suggested by the software to forecast costs/ha for the next 24 months, DTN-S was able to capture the expected scenario for a near-term trend (730 days) for the cost/ton in
Figure 3A, while ARIMA was used for
Figure 3B.
The minimum cost/ha/soybean value for
Figure 3A (urea) was USD 33.90, and for
Figure 3B (NPK 05-25-25 fertilizer) it was USD 139.20. The average values were US
$ 58.04 and USD 288.02, and the maximum values were USD 120.15 and USD 602.62, with a standard deviation of USD 29.32 and USD 161.58, respectively. The purchasing power of rural producers to acquire one ton of fertilizers was reduced until July 2022, when a recovery trend began, observed in October [
42]. As of April 2023, the price of one ton of NPK 05-25-25 fertilizer is US
$ 696.00, and the price of urea fertilizer is US
$ 718.00 [
57]. These values are considered above the average predicted in this analysis. The difference between the maximum and minimum values presented in this analysis was significant.
Using the penalizing criteria of AIC and BIC, the software found the best model for all the simulations performed. Knowing that the model that best fits the series is the one with the lowest value, it can be concluded that the most suitable model for
Figure 3B is the ARIMA (1, 1, 2) series. The model indicates an order of 1 for the AR component (Auto Regressive), an order of 1 for the 2 component (Integration or differencing), and the last 2 for the MA component (Moving Average). The values for AIC were 5.99 and for BIC were 6.10* for
Figure 3B, based on the lowest mean squared error. For
Figure 3A, the AIC was 3.32 and the BIC was 3.36*.
The ARIMA model for
Figure 3A showed that the series has an insignificant auto-regressive (AR) component. This is due to the partial autocorrelations of the series, as evidenced by the ARIMA (0, 1, 1) model. However, even so, the autoregressive coefficients and the model coefficient weighted the behavior of the forecast, increasing the accuracy of this variable, thus demonstrating an appropriate model. Additionally, it can be observed that the Durbin-Watson (DW) statistic values, which indicate no first-order correlation, whether positive or negative, are equal to 2.0 for
Figure 3A.
The TANS model for
Figure 3B demonstrated that the series has a non-stationary stochastic process, as the statistical properties of at least one finite sequence of components differ from those of the sequence for at least one integer. In other words, a non-stationary stochastic process is one where the joint distribution of any set of variables changes if we change the variables over time. This is due to the partial correlations of the series, as evidenced by the ARIMA (1, 1, 2) model. Additionally, it can be observed from the Durbin-Watson (DW) statistic values that there is first-order correlation, whether positive or negative, with values close to 2.0 for
Figure 3B.
The results from
Figure 4 refer to the projected values of dolomitic limestone corrective. The forecast indicates a stable scenario for the next 24 months. The minimum cost/ha/soybean/corn value from
Figure 4 was USD 14.80. The average value was US
$ 25.29, and the maximum value was USD 40.98, with a standard deviation of USD 8.02.
The current cost of dolomitic limestone corrective per hectare is US
$ 25.3 [
57], which falls within the predicted average. The literature indicates that the costs associated with this soil corrective are mainly influenced by the freight rates during its transportation [
71].
According to the Predictor, for
Figure 4, the best method with the lowest mean squared error chosen for all groups was the Damped Trend Non-Seasonal. Further-more, it can be observed that the values of the Durbin-Watson statistic indicate not first, second, or third-order correlation, whether positive or negative. The analyzed product is essential for the cultivation of corn/soybean, as soil acidification is a concern in almost all countries with significant production of these crops, and its reversal con-tributes to water and nutrient exploitation, aiding the plant during periods of drought [
72].
The results in
Figure 5 pertain to the projected values of the Fungicide Trifloxystrobin Tebuconazole, which showed a strong relationship with the production costs of corn and soybean. The forecast indicates a scenario of price increase for the next 24 months. This fungicide was the only agricultural pesticide with R² ≥ 0.70 for both crops, and thus, it can influence the increase in production costs for the studied crops.
The minimum cost per hectare for soybean/corn, as shown in
Figure 5, was USD 25.43. The average cost was USD 28.92, and the maximum cost was USD 33.99, with a standard deviation of USD 2.64. According to the IEA (2023) [
57], the current cost of Trifloxystrobin Tebuconazole per hectare is USD 28.9, indicating that although there is a trend of price increase for this input over the next 24 months, the average cost remained within the estimated price by this forecast.
The statistical results conducted, according to the Predictor, showed that the best method with the lowest mean squared error chosen for all groups was DTN-S. This method is efficient for data with trends but without seasonality [
33], which was the case in this analysis.
The projected values for soybean seed are presented in
Figure 6. The results correspond to the projected values for both analyzed crops as dependent variables (corn/soybean). The forecast indicates a scenario of price increase for the next two years. The minimum cost per hectare for soybean seed was USD 34.29. The average cost was USD 79.93, and the maximum cost was USD 137.14, with a standard deviation of USD 33.28. The current cost of soybean seed per hectare is USD 79.9 [
58]. This value also falls within the predicted average of this study.
For the variable Soybean seed, the most suitable method was DES. The results showed that the values of the DW statistic among all groups are close to 2.0.
The results from
Figure 7, presented below, refer to the projected values and trends for the costs related to the labor aspect of tractor drivers and day laborers for both crops (corn/soybean).
Figure 7A and 7B depict the trends for these variables, respectively. Both variables indicate an upward trend for the next 24 months.
The minimum cost per hectare for corn/soybean as shown in
Figure 7a was US
$ 2.52, and for
Figure 7b it was US
$ 3.31. The average costs were US
$ 2.83 and US
$ 3.84, and the maximum costs were US
$ 3.23 and US
$ 4.72, with standard deviations of US
$ 0.22 and US
$ 0.42, respectively. The average values obtained from the forecast align with the current values of US
$ 2.83 for tractor driver labor and US
$ 3.84 for day laborer labor [
57].
The ARIMA models for
Figure 7a and 7b demonstrated that the series has an insignificant autoregressive (AR) component. This is evident from the partial autocorrelations of the series, as shown in the ARIMA (0,2,0) model. The values of the DW statistic indicate that there is no first-order correlation, either positive or negative, with a value of 2.0 for
Figure 7a and close to 2.0 for
Figure 7b.
The results presented in
Figure 8 are related to the projected values for the price trend per bushel of corn in the near future. However, it is evident that there is a stable price trend for corn per bushel in the coming months (24 months).
The minimum price per bag for corn, as shown in
Figure 8, was USD 5.66. The average price was US
$ 11.28, and the maximum price was US
$ 18.53, with a standard deviation of USD 4.52. The current price is USD 11.3, which falls within the predicted price range of this analysis [
57].
Using the penalizing criteria of AIC and BIC, like
Figure 3a, the ARIMA (1, 1, 1) model was found to be the best fit for the series. The AIC value was -0.65, and the BIC value was -5.58*, based on the lowest mean squared error.
The statistical values for the MCS analysis conducted using the predictor, for
Figure 3 and
Figure 8, are presented in
Table 4.