1. Introduction
Global warming is the increase in the Earth’s temperature and has a significant impact on water supply; over the last 33 years, water demand has increased considerably, while water supply has been precarious [
1]. This distribution of water resources will be further unbalanced at the river basin level, where agricultural production will be influenced by these complex movements of the water deficit [
2], by significant projected climate changes, including unprecedented global mean surface temperature increases since the mid-20th century (1.5 to 5.0 °C) [
3], and reduction in precipitation rate in summer (−25%) [
4], leading to a higher frequency of these extreme weather events [
5] attributed to climate change, which is defined as the change in climatic elements in a given period [
6].
Climatic variables, mainly precipitation and temperatures, are changing [
7], affecting crop growth and productivity [
8]. These effects mostly turn out to be adverse, becoming a major global threat during the dry season due to increased temperatures and decreased precipitation [
9]. In developing countries, this situation is aggravated by the fact that agricultural activities are more sensitive and vulnerable to climatic conditions and climate change, as well as by different resource, technological, and institutional constraints [
10]. In addition, climate change and precipitation shortages limit agricultural production and significantly impact rainfed crop production [
11]. The increase in temperature threshold and water scarcity affect the development of the different phenological phases [
12,
13] in potato crops, mainly in the formation of tubers [
12].
Climate change is one of the world’s most crucial concerns. It is a significant threat to the global food supply, mainly in family or subsistence farming [
13], because it influences the primary conditions of agriculture [
14], which are carried out with scarce resources, directly affecting the quality of life of farmers [
15]. Agriculture is the mainstay of the economy and contributes to the food security and employment of rural households [
16]; however, under the conditions of climate change and variability in the availability of water resources, adopting efficient irrigation systems, cultivating crops better suited to withstand drought conditions, implementing sustainable agriculture practices, adopting the strategy of climate-resilient sustainable agriculture (CRSA), and reducing our reliance on rainfall will be necessary to address this challenge to ensure crop production and guarantee food security [
1,
17,
18]. Also, sustainable agriculture provides a potential solution to enable agricultural systems to feed a growing population while successfully operating within the changing environmental conditions [
19]. Rainfed agriculture is currently one of the main economic activities most affected by climate change due to its significant social and economic consequences for human well-being [
20].
Many approaches have been used to investigate the impacts of climate change on agriculture [
21] using the AquaCrop model in a variety of seasons and locales; in all of them, good model performances were obtained [
22,
23]. However, the Peruvian Altiplano has particular characteristics, where rainfed agriculture is the principal agricultural production system and most vulnerable to climate change [
24], so it is essential to study the impacts of climate change and to develop and improve practical assessment tools, which are crucial to reducing uncertainty in agriculture [
25]. Therefore, in this research, we propose and evaluate the yields of the rainfed potato crop under climate change scenarios using the AquaCrop model in the conditions of the Peruvian Altiplano.
4. Discussion
The efficiency results of the simulation of rainfed potato crop development and production in the AquaCrop model in the calibration and validation stages showed satisfactory results. Despite slight over- and under-estimates of the model in canopy cover, biomass, and yield, which were also reported by other studies for the cultivation of potatoes [
23,
35], these results suggest that the AquaCrop model can satisfactorily simulate the development and production of rainfed potato crops under the extreme climatic conditions of the Peruvian Altiplano, since it simulates canopy cover, dry aerial biomass, and crop yield very closely to the observed values. The results obtained are consistent with previous research, which showed excellent performance of the AquaCrop model for simulating the work of different crops in different regions [
34,
35,
45]. For example, in Ethiopia [
23], coefficients of determination values (r
2) greater than 0.92 were found for the relation between observed and simulated values of canopy cover for potato crops under deficit irrigation, which are similar to those determined in this study (>0.95). In relation to the values of NRMSE, NE, and d, we found identical values to those obtained for Ethiopia, which suggests a high degree of adaptability of the AquaCrop model to different climatic conditions, soils, and crops.
Once the AquaCrop model was calibrated and validated, potato crop yields were simulated for the extended period (2005–2017). The simulated average annual yield results (
Table 6), when compared with the yield statistics of the Dirección Regional Agraria Puno (DRA) for the province of Azangaro [
46], show a good approximation. The mean difference analysis (t-Student) performed on the observed and simulated potato yields indicates no significant differences at a 5% significance level (t-statistic = 0.47 and t-tabular = 1.81). It suggests the AquaCrop model can adequately simulate potato crop yields for periods other than those used in the model calibration and validation. However, differences in potato crop yields can be attributed to various factors, including crop variety, local climatic conditions, irrigation rates, fertilization, and agricultural activities [
34,
47].
Potato yield statistics for the province of Azangaro averaged 9.72 t yr
−1 (
Table 6), which is compared to regions with similar climatic and geographical conditions, such as the Mantaro Valley in the central Andes of Peru, where higher yield values of up to 18.9 t yr
−1 were observed [
48]. The vital difference in yields could be attributed to the annual rainfall amounts, which are higher in the Mantaro Valley (833 mm) compared to Azángaro (597.8 mm), as crop yield is directly related to biomass, and biomass is directly related to the amount of water available, which generates a more significant expansion and coverage of the foliage [
49]. Therefore, dependent on annual rainfall amounts, potato cultivation under rainfed production systems causes crop water stress periods, significantly influencing the potato crop’s phenology, growth, and productivity. Therefore, it is necessary to practice irrigated agriculture by implementing irrigation systems that allow the timely provision of water to crops and reduce periods of water stress to obtain better yield levels [
23,
28,
50].
According to projections for the period 2023–2050, changes in precipitation in Azángaro were not as significant as in other regions of the Altiplano [
51,
52]; therefore, it is expected that the conditions of the Peruvian Altiplano, such as hailstorms, snowfalls, frosts, and droughts that are persistent [
53], affect productive activities in a negative way [
53]. However, contrary to the results obtained in this research [
54], it found a positive trend for the projected period (2071–2100), with an increase of up to 2 mm day
−1, agreeing with the results of [
55]. This behavior would be attributed to the scarcity of meteorological information in the region, the geographical conditions of the Altiplano, and the uncertainty of projections obtained from global climate models, among others [
56], which could be improved with the use of regional climate models [
57].
The changes in mean temperature projected for the experimental area are conservative in comparison to previous research that determined rates of increase of 0.8 to 2.7 °C century
−1 [
58]. Furthermore, in the projections made by [
54], the increases would be between 2 °C and 4 °C and up to 6 °C in the north of Lake Titicaca (2071–2100). Likewise, Galera and González [
59] indicate temperature increases of up to 4 °C, generating favorable conditions for certain crops, with production increases due to changes in the climate. The temperature has a significant effect on the yield of the potato crop. The optimum maximum and minimum temperatures are in the range of 13.52 °C and 3.75 °C, respectively. Values above and below this range would negatively affect the crop yield because these are extremely sensitive to environmental changes. Values above the optimum modify the growth mode according to the duration of the different phenological phases, which would significantly affect the yield achieved due to the decrease in the number of tubers [
60,
61].
The changes in potato crop yields found in this research for the RCP 4.5 and RCP 8.5 scenarios showed differentiated behaviors for the periods 2023–2037 and 2038–2050, with minimal reductions for the former and more significant decreases for the latter periods; these results are in line with those found in previous studies [
60,
62,
63,
64]. Changes in rainfall and temperature modify the different phenological stages of the crop, affecting yields by reducing the number and size of potato tubers in rainfed crops [
7,
60,
64,
65]. Since the potato crop requires 400 mm to 800 mm of rain per agricultural campaign for adequate production [
29], values slightly lower than this range were obtained in this research: 382 mm for RCP 4.5 and 390 mm for RCP 8.5, which generated a minimal reduction in crop yield under a rainfed agriculture system. Likewise, droughts represent a severe threat to agricultural development and food security [
45] due to the deficit in precipitation and the increase in temperature, generating a tendency for production to decrease in the coming years, which would require the implementation of irrigation systems, resulting in higher water demand, according to [
66].
Under these current conditions in the Peruvian Altiplano, the introduction of heat-tolerant and drought-resistant potato genotypes [
67,
68], as well as the cultivation of bitter potato varieties [
69], the development of irrigated agriculture reversing the loss of traditional knowledge [
47], the adoption of sustainable agricultural practices [
17], the adoption of strategies for climate-resilient sustainable agriculture (CRSA) [
18], and techniques to reduce crop water loss [
70], are required as an essential strategy for adapting to climate change and variability, as these are issues of current global concern due to their impact on agricultural production [
71].
5. Conclusions
In general, the AquaCrop model performed well in simulating the development and production of the potato crop variety Imilla Negra (Solanum tuberosum spp.) under the extreme climatic conditions of the Peruvian Altiplano, adequately enacting the observed values of canopy cover, aerial dry biomass, and crop yield for the period 2017–2018.
Climate projections showed decreases in precipitation and increases in temperature and evapotranspiration for the RCP 4.5 and RCP 8.5 scenarios in 2023–2050. Projections for potato yields in the Peruvian Altiplano under the climate scenarios showed a minimal decrease in the first half of the projection period (2023–2037). In the second period (2038–2050), the reduction increased due to climate change.
In addition, further research and field experiments are needed to determine the influence of other factors, such as potato crop variety, local climatic conditions, irrigation doses, fertilization, and agricultural activities, on potato crop yields in the Peruvian Altiplano, from which to promote strategies to adapt to climate change and ensure the food security and well-being of the communities of the Peruvian Altiplano.