Introduction

Due to its nutritional characteristics and availability throughout the year, guava (Psidium guajava L.) is located within the top ten fruits consumed in Mexico. In 2015, an area of 20.6 thousand hectares was harvested and a production of 293 thousand tons was obtained, generating an economic pledge of 1 330.60 million pesos and representing an important source of temporary jobs in the producing areas. The production of guava is an activity that generates about 4 million wages and has more than 4 500 producers in the 19 producing states of the country (^{SAGARPA, 2009}). The states of greater importance in the production are Aguascalientes, Michoacán, Zacatecas and Jalisco (^{SIAP, 2016a}).

Aguascalientes concentrates 0.3% of the agricultural area of the country. The main agricultural products that the entity produces are maize, beans, guava, oats, pastures, alfalfa, nopal, grape and peach, also produces vegetables such as lettuce, garlic and chile. Maize production is the most important in the state, as it occupies 70.9% of the area sown; however, national recognition, determine that guava is one of the most representative crops of Aguascalientes.

The main guava producing area in Aguascalientes is located in Calvillo municipality, which occupies 16.6% of the state’s territory (^{INEGI, 2009}); this municipality is the second producer of guava at the national level and has a planted area of 6 269 hectares that produce, on average, 90 thousand tons annually (^{SIAP, 2016b}). The guava cultivation occupies 4.7% of the state surface and generates more than 5 000 annual jobs directly and indirectly, the annual precipitation in the municipality oscillates between the 500 and 800 mm, and is insufficient for the crop reason why it depends on irrigation (^{SAGARPA, 2009}; ^{González et al., 2000}).

As a perennial crop, guava is faced with cyclical behavior patterns that are reflected in price ups and downs. Data from the national market information and integration system (^{SNIIM, 2016}) indicate the existence of high prices in months of low production and low prices in months of high production.

The seasonal variation of prices is not only present in guava, the temporary variation of prices is a problem faced by most Mexican farmers, the behavior of prices fluctuations is the result of disinformation, planning, climatic conditions, pests, yield level and product availability that is introduced to the market (^{FAO, 1993}) . This causes market saturation and the seasonal fall in prices (^{Fundación Produce Guerrero, 2012}).

Based on information obtained from ^{INEGI (2016}; ^{SIAP, 2016a}; ^{SNIIM, 2016}), a function was estimated where the relationship between production as an independent variable and prices was the dependent variable. A linear regression analysis of wholesale prices and production over a four- year period (January 2012 to December 2015) yielded the coefficients of determination, ranging from 0.54 to 0.85. Table 1 shows that, in the case of a 1 000 tonne increase, the wholesale price would decrease by 30, 40, 20, 30, 20, 40, 10, 20 and 10 pesos per ton in Aguascalientes, Chihuahua, Cd. Juárez, Torreón, Durango, Gómez Palacio, Monterrey, Mexico City and Guadalajara, respectively. In addition, it was also observed that there is no control in the production and shipping flows of guava from the state of Aguascalientes, so that wholesale prices can be transmitted to producers causing problems and losses in profits for productive agents.

There are several studies that present alternatives to reduce price volatility and stabilize markets, crop subsidies, financial insurances, technology implementation, crop scheduling, flow control are just some of the solutions that guava producers possess to reduce price volatility generated by the dependence to weather conditions (^{FAO, 2010}; ^{FAO, 2011}; ^{García-Vásquez et al., 2011}; ^{García-Salazar et al., 2014}).

The guava cultivation manages to obtain production all year long using the calmeo technique, which consists of introducing the tree in a period of irrigation suspension for a period of one to six months during the dry season from the end of the previous harvest (^{González et al., 2002}). This technique is used by the producers of Calvillo to achieve a better agronomic management, pursuing as a purpose to conserve their plots or obtain higher prices.

The technique is performed after harvest and its duration defines the time of the next harvest, this technique is used to schedule production, there is also the early calmeo from June to August and late calmeo from January to March (^{González et al., 2002}).

The guava fruits are very susceptible to damage by cold and diseases, resulting in browning (oxidation) (^{Mata and Rodríguez, 2000}). In Aguascalientes there is no cold network that allows the storage of fresh consumption guava that manages to control flows for better profits, storage consists mainly of having control of product availability that is sent to the market.

Storage has been successful in several countries and with certain crops, in the case of highly perishable products such as guava, storage is possible for a short period of time. The guava must have certain characteristics so that the storage is successful, the storage process of guava begins with the selection of the fruit; green guavas with yellow shades to be stored at 5 to 10 °C (^{SAGARPA, 2008}). It is committed to the “late calmeo” as a productive technique for the planning of Calvillo guava production, which would allow reducing price volatility and increasing market share and producer profit. The objective of this paper was to analyze the guava market to give policy recommendations that give elements to achieve market order, and to determine the best strategies to raise the price of guava in Calvillo municipality. The “calmeo” technique and storage were analyzed as main control actions of the supply.

Materials and methods

Indicators were estimated and it was necessary to estimate a regression model using a linear regression model to determine the impact that the quantity of guava produced by Aguascalientes has on wholesale prices at the country's wholesale markets. The analysis is based on the theory of the company, so the profit was determined through the difference between the total revenue from the sale of the state guava and the total costs incurred to achieve yield and marketing (production, transport and storage).

For the analysis, only the state of Aguascalientes was taken as the producing area and nine consumer markets were also considered. The total gain (G) was calculated by discounting to the sales revenue (in the domestic and export market) the production costs, transportation costs and storage costs.

Considering i(I=1) municipalities producing guava and j(J=1, ...9) consumer markets, total sales revenue were obtained as follows:

Where: for the month t; pc ijt= the price of guava in the domestic market j; xijt= the amount of guava sent to the national market j; peiet= the export price at the border e; xiet= the amount of guava sent from the producing area to the foreign market by the border e.

The total cost of production is given by:

Where: cp_it= the production costs of guava in the producing area; xit= the amount of guava produced in Aguascalientes.

The total cost of transportation is equal to:

Where: for the month t, ct_ijt= the transport cost from Aguascalientes to the consumer wholesale markets j; x_ijt= the amount sent of guava from Aguascalientes to wholesale markets j; ct_iet= the transportation cost from Aguascalientes to exit points of exports e.

Finally, the total transportation cost is calculated as follows:

Where: for the month t, ca_{it, t+1}= the cost of storage from the month t to the month t+1; x_{it, t+1}= the guava amount stored from month t to month t+1.

A total of nine wholesale markets were considered: Aguascalientes, Chihuahua, Cd. Juárez, Cd. De México, Coahuila, Durango, Gómez Palacio, Guadalajara and Nuevo León, a municipality producing guava (Calvillo) and 12 periods of time (January to December). The impact of the quantity produced on the wholesale price of the guava at the wholesale markets was estimated as follows:

Where: α_ijt= the intercept and β_ijt= a coefficient that measures the relationship between the price and the quantity of guava produced in Aguascalientes.

The estimation of the total gain was made considering three scenarios: 1) the first shows the situation observed in the average period 2012-2015 (base situation); 2) the second showed a 8.5% decrease in production in months of oversupply (October to January) thanks to the “calmeo” technique and a production increase in the months of February to September according to historical records reported by the SIAP (2012-^2016a); and 3) the third scenario considered the storage of 10% of the production in the months of maximum harvest, in order to control the product flow to the market. The consumption of guava produced by Aguascalientes took data from the guiding plan of the national guava product system committee (SAGARPA, 2012), it was considered the shipment of guava from Aguascalientes to the different destination wholesale markets.

Guava production during the analysis period was obtained from ^{SIAP (2016b)}. Wholesale prices and demand points (wholesale arkets) were obtained from ^{SNIIM (2016)}, the national index of consumer prices that deflated prices was obtained from ^{INEGI (2016)}.

Production costs were obtained through a survey to 28 guava producers in the state. Storage and transportation costs were obtained through interviews with marketing agents. Transport costs were obtained by multiplying the average costs (pesos per t-km) by a distance matrix. The unit transport costs were obtained through the following regression ctiet= 220.84+0.77 km+43.69 D, where the dichotomy variable takes value 2 for distances greater than 1000 km, the value of 1 for distances between 501 and 1 000 and 0 for distances less than 500, the coefficient of determination was 0.75.

The monthly exports of Aguascalientes state to the United States of America were obtained from ^{SICAGRO (2016)}, ^{SE (2016)} and ^{USITC (2016)}. The data considered correspond to the average period from January 2012 to December 2015. The difference in wholesale and producer prices was considered to determine the percentage of participation of producers and marketing agents.

Results and discussion

Guava in Aguascalientes has seasonal patterns that concentrate production, harvest and marketing in the months of October to January; in these months there is a high dynamism in the Calvillo municipality since it harvests approximately 41% of the state production and 75% of the area planted with guava. It is estimated that of the total crop 4.9% is destined for exports and this represented 52.1% of the national exports. 14.4% of the guava production goes to industry and the losses correspond to 5.7% of the total production, which in 2015 was 90 thousand tons.

Conclusions

Currently the guava producers of Aguascalientes face the problem of price volatility that diminishes their levels of income and profits. Volatility in prices is a consequence of the lack of planning in the product harvesting throughout the year. Some control actions of the supply would allow to avoid the fall of the prices improving the income and the gain of the guava producers. The “calmeo” technique would significantly increase the income and profit of guava producers in the entity. Although it would not be advisable because of the heavy investment required, a more uniform flow to the market could be achieved by storing a percentage (eg 10%) of the yield obtained in the peak harvest months. Both actions require the organization of the producers, since their dispersion explains to a large extent the situation of price volatility they are currently experiencing.