Agroclimatic risk zoning of lemon ( citrus aurantifolia ) in the hydrographic basin of Paraná River III , Brazil

The lemon tree is one of the most important variety of fruits in Brazil, considered the fifth largest world producer. The purpose of this study was to carry out agroclimatic risk zoning for lemon (Citrus aurantifolia) in the basin of Paraná River III. Technical maps through interpolation and regressions, and graphics for risks analysis probabilities were elaborated. The agroclimatic risk for lemon was established according to the species requirements, such as precipitation, water deficiency, average and maximum air temperature, thermal unit/degrees days and risk of frost. Larger region in the basin is recommended for cultivation of lemon. It was not found inapt areas for cultivation, only restrict, exhibiting considerable potential for cultivation of lemon, in the region of study.


Introduction
The climate is the key variable that most interferes in the establishment, propagation and adaptation of fruticulture. The Tahiti acid lemon, known as Tahiti lemon (Citrus latifolia Tan) is among the ten most important fruit varieties produced and market in Brazil (FAO, 2017). Brazil has a continental territory and significant part is considered as tropical climate, appropriate for cultivation of lemon. According to the FAO (2017), Brazil occupies the fifth position in the world production of limes and lemons, producing approximately 1.3 million tons.
The basin of Paraná River III presents areas of relevant agricultural potential due to its climatic variability. Its thermal and water regime has different variations during the year (CALDANA et al., 2019). The lemon has unexpressive production in the region. The numbers for the 2017 and 2018 confirm this condition. The registered productions were not greater than 400 tons (391 and 400 respectively), harvested in 40 hectares (IPARDES, 2019). There was no expansion of areas, indicating that production is concentrated in the hands of a few farmers. The Paraná State, Brazil, at the same period, produced about 16 thousand tons of lemon (IPARDES, 2019).
The acid lime Tahiti is characterized by producing fruits with medium to large size of 70 to 100 g and devoid of seeds. The plant is medium to large in size, blooms all year and the fruit ripens between 120 and 170 days after flowering (MARCONDES, 1991; Agroclimatic risk zoning of lemon (citrus aurantifolia) in the hydrographic basin of Paraná River III, Brazil CALDANA, N. F. da S.; ALVES, S. D. ;MARTINS, A. J.  STUCHI et al., 2003). Fruit development varies according to the canopy variety, rootstock used, thermal regime and water availability in the producing region (SAM et al., 1988).
Flowering in citrus occurs after low temperatures or deficiency of water, which act in differentiating and breaking dormancy of flower buds, especially in branches with 6 to 18 months that do not have fruits (MATTOS et al., 2003b). At the global scale and in the context of sustainable agriculture and climate change, several studies are carried out to improve citrus management and production techniques (ZHAO et al., 2017;AL-AAMRI et al., 2018;NDO et al., 2019;OWI et al., 2019;LADANIYA et al., 2020).
From this, the destination of the fruits is the consumption in domestic or external markets or for juice. The essential oil extracted from the peel has industrial use as food flavorings and perfumery ingredients and cab be used as medicinal herb such as digestive stimulants, antioxidants and homeopathic formulations (MATTOS et al., 2003a).
In this sense, and considering the inexpressiveness of acid lime in the area of this study and its considerably the economic potential, the purpose of this study was to carry out agricultural zoning of climatic risk for lemon trees in the hydrographic basin of Paraná River III. For this, the requirements were raised hydroclimatic species and meteorological data of annual, seasonal, monthly and daily time presenting series from 1976 to 2018 for knowledge of the local climate.

Climate Variability
The hydrographic basin of Paraná River III is located in a Cfa climate, which means that it has a humid subtropical climate according to the Köppen climate classification. This is characterized, mainly, by the absence of drought seasons and by The spatialization of these data was performed by interpolation, it was done using (1) (4)

Where
Tn is the average temperature of month n (n = 1 is January, n = 2 is February, etc.) in °C, and I is an index that expresses the heat level of the region.
The value of I depends on the annual temperature cycle, integrating the thermal effect of each month, and is calculated using the formula .
The exponent "a", being a function of I, is also a regional thermal index, and is calculated using the expression .
The PET value represents the total monthly potential evapotranspiration that Agroclimatic Risk Zoning Factors a) Annual precipitation: We selected data on monthly and annual precipitation from meteorological series of 27 meteorological stations in the basin. The results obtained were interpolated in a geographic information system for the generation of maps with the regionalization of data through the IDW. Was admitted risk of annual precipitation less than 1500 mm and presenting an adequate precipitation during the year, with, approximately, 120 mm monthly (SANTOS FILHO et al., 2005). b) Annual Water Deficiency (AWD): Was estimated using the method of Thornthwaite and Matter (1955), and obtained by calculating the normal climatological water balance for the weather stations. We consider 100 mm for the water capacity in the soil (SOUZA et al. 2006). The results obtained were interpolated using the ArcGIS 10.0 geographic information system to generate the annual water deficit maps. The following thresholds were considered for the risk of water deficiency: high risk-AWD > 100 mm; low risk-AWD < 100 mm ( For the creation of thematic maps and the final zoning map, ArcGIS software was used. Firstly, the numerical values from the meteorological stations were transformed into points, according to their geographical coordinates. We then used the edaphoclimatic requirements of the avocado species to produce data spatialization, which was used for the delimitation of the representative bands of the avocado climate requirements. Thus, the station values were replaced by "1. Apt" or "2. Restricted", according to the physiological requirements for each meteorological variable analyzed.
The next step was to combine the matrix images. Each pixel was assigned with the values "1" or "2", as already described. If the combination for a point was filled only with values "1", the region was classified as fit. If it had a value of "2" it was restricted by a given variable. If two or more "2" values were assigned, the location was classified as unfit.
Then, standardization of the pixels using classifications was performed by dissolving the vector classes. In this way, the agroclimatic zoning classes were grouped, thus defining regions of suitability for the studied species. The final map showing the agroclimatic zoning of each crop will provide an estimate of the representative area of each risk class, ensuring its suitability for the site.

Results and Discussion
The precipitation of the basin of Paraná River III was not restricted for cultivation of lemon tree (map 2). The annual requirements for citrus are between 900 mm and 1,500 mm (SANTOS FILHO et al., 2005). As noted in the graphs, precipitation less than 1,000 mm does not occur in the region, but less than 1,500 mm can occur frequently, but does not present a risk to production of lemon. The lowest record was 1680 mm at the northern end of the basin in the Guaíra region.
Acid lime is a drought-resistant species. In the North, Northeast and Midwest regions of Brazil, apt regions are classified with water surpluses above zero and annual water deficiency below up to 300 mm. For the production success limit in the South, the acceptable limit in the water balance was 100 mm (SANTOS FILHO et al., 2005).
Map 2 -Annual rainfall average in the hydrographic basin of Paraná River III.  (2020) However, as noted, even in extremely dry years, such as in 1978 (map 2), the water balance exceeds the acceptable average of water deficit for production in Brazil. The producer should be aware that, in the event of extreme drought or prolonged summer, water deficiency causes the citrus leaves to curl, the most evident symptom in regions with a warmer and drier climate. This symptom subsequently leads to partial closure of the stomata and reduced sweating and photosynthesis, due to dehydration of the canopy of the plants, under conditions of water limitation, which can cause serious losses to production (MACHADO et al., 1999;SILVA et al., 2005;VOLPE et al., 2009).
For the water balance verified in the region (graphics panel 1) as the risk observed was 100 mm accumulated annually, no season presented a risk for the cultivation of the lemon tree. In municipality of Guaíra, that presented significant deficiency, the accumulated figure was 56 mm. The extracts show less favorable water balance in the months from January to April, thanks to high temperatures and an increase in evapotranspiration, and the farmer have to pay attention to the species during this period, Map 4 -Annual average and maximum temperature and probabilities of extreme temperature occurrences for the lemon, in the basin of Paraná River III.
Through the graphs, a risk of 38°C was identified in just one decade of Cascavel, with a probability of occurrence of 4 %, even if temperatures above 35°C remain low in this season, not exceeding 30 %. In municipality of Toledo, the risk remains low as well, not exceeding the probability of occurrence of 10 % per 10-year period.
In municipality of Guairá, temperatures above 35°C showed a high frequency in the spring and summer months. The risk of temperatures above 38°C increases in that season, but does not present a risk greater than 20 %. The strip near the Paraná River channel is not inapt for cultivation due to this variable, however, it is restricted, and the To recommend the planting season, attention should be paid to the fact that citrus orchards are more sensitive to water deficit during budding, flower buds emission, fruiting and the beginning of fruit development until it reaches 2.5 cm in diameter, when the demand for water is considerable (SANTOS FILHO et al., 2005). It is recommended the They indicated that frost tolerance was studied at 2°C, as it has a wider range of species, in addition to ascertaining the thermal sum of the degrees day and precipitation. Only a small strip in the northwest of the state proved to be apt, other areas should use rootstocks for protection from extreme cold, or even, they had insufficient thermal sum. The latitudinal factor interferes with citrus production, since these adversities were not present in the basin of Paraná River III.
It should be noted that zoning does not eliminate the risks, but only presents more favorable conditions for the development of lemon tree orchards. As agriculture is a risky activity, all activities are susceptible to climate extreme events, which may or may not cause harm for the farmer. In the context of sustainable agriculture and climate change, agroclimatic zoning provides greater security in decision-making, agricultural planning, in the hydrographic basin of Paraná State III.


The hydrographic basin of Paraná River III has a significant area with aptitude for cultivation and considerable perspectives through meteorological variables for the development of the lemon tree.
 Precipitation and water balance presented sufficient values in all scenarios studied for cultivation of lemon.


No area was inapt for more than one meteorological variable. Only two bands were restricted, in the west by high temperatures and in the east by severe frosts.
 Agricultural management techniques can be taken to avoid the risk of severe frost and to mitigate the impacts of extreme temperatures and to avoid areas with a higher incidence of the phenomenon to ensure greater possibility of success in the cultivation of lemon in the basin of Paraná River III.