Introduction

In the community of Vicente Guerrero have established an agroforestry system called "trees in cropland" as an organic alternative to produce food, where they have implemented ecological techniques for handling, as board ditches for soil conservation and production of organic fertilizers with materials in the region (^{Magdaleno, 2005}). One of the main challenges of this type of agroforestry system is to achieve adequate energy and protein for the family food availability in regions where market access is limited and insufficient income (^{Márquez et al., 2011}).

The objective of this research was to study the organic agroforestry system of a peasant family in the community that would identify material flows and satisfaction of nutritional requirements and the conservation of soil resources, in order to prove their efficiency and impact on food sovereignty and generate a model for replication elsewhere. Specifically, the intake of carbohydrates and protein crops established for comparison with the food requirements of the family and the changes were observed in some properties and characteristics of the soil in the areas of annual crops in two years was estimated rotation.

Background

Materials and methods

The Españita municipality belongs to the state of Tlaxcala, which is located in the central Mexican highlands region. The municipal head is located at an altitude of 2 640 meters, its geographical position according to the INEGI (2010) is 19° 27'4'' north latitude and 98° 25' 23'' west longitude. It borders the following municipalities: north Sanctórum of Lazaro Cardenas, south Ixtacuixtla, east Hueyotlipan, and west Sanctorum of Lazaro Cardenas and the state of Mexico (Figure 1).

Figure 1 Location map of the community of Vicente Guerrero. 

The area belongs to a mountainous tropical region, but with polar influences, which is manifested in a low annual temperature oscillation (± 6° C), in a summer rainfall regime and the influence of winter cold fronts. Its altitude and position to leeward determine the predominant climate is humid temperate type (Cw1) (^{García, 1973}), which is characterized by normal annual average temperature of 12.9° C. The months with the highest are april and may, the coldest january and december; the annual average rainfall is 742.7 mm, with the highest incidence of june to september.

The plot where it was carried out the study was chosen with the participation of representatives of the community, is owned by the Sánchez Sánchez family. It has an approximate area of one hectare, which has a moderate slope where soil conservation have been made by development of terraces and contour furrowing.

The field is divided into six subplots or terraces annual agricultural crops such as corn, beans, squash, and oatmeal. Among them are five boards with fruit trees pear, peach, apricot and plum trees and other perennials. It also has an area with some animals like sheep, turkeys, chickens and horses, all under agro ecological management.

The study began with the identification of the inputs and outputs of the agroforestry system of the whole plot, for which a location sketch of the agricultural, forestry and livestock components was developed. For agriculture were taken into account acreage by crop, planting date and harvesting, planting density, performance and crop management (cultural practices, tools used, workmanship, date and amount of fertilization and inputs for pest control). A technical table was prepared for each crop where the number of wage and work time required for each culture was recorded.

For the forestry component (fruit trees and other perennials) an inventory was made. The parameters taken into account for livestock are: species and number of animals. Once all components of agroforestry system inputs and outputs identified were classified with this information a scheme system was performed.

To complete the flows of inputs and outputs of the system was carried out a log of activities during an agricultural cycle, which contained the following information: date, activity, implement and tool to use, time spent on the activity and labor used.

The area planted to each crop in each of the terraces and visits were made to verify the crops sown during the twoyear research period was estimated (Table 1).

Table 1 Crops sown in the plot of Vicente Guerrero in 2011-2012. 

Subsequently, by monitoring visits crop management came to know the cultural tasks performed on the plot. The estimated yield of each crop was made by sampling to quantify production. In the case of corn four samples were taken for each subplot where it was seeded plants had over 10 m above the groove is cut, the number of plants counted, weighed, cobs were obtained, weighed. Later they were shelled and the grain was weighed to measure performance.

In the case of beans and bean four samples were taken from subplot in rows six meters long. He threshed and weighed to estimate grain yield. In the case of oats a sample of 1 m2 was taken and weighed as dry matter, since this use it as fodder for animals. Fruit trees in production was estimated based on sampling and data provided by the producer.

Once the weight data collected and total area planted was extrapolated for performance and production on the parcel annual and perennial crop. With these data and tables that issued the National Institute of Nutrition Salvador Zubirán and published as Mexican System Equivalents food, the nutritional content of carbohydrates and proteins each crop were considered and overall contributions of these were calculated that the system has to find out whether they are sufficient to feed the family, when compared with the nutrient requirement per person.

To observe changes in soil properties of two samples per year, one before sowing and another after harvest were made. For each sample composite samples from three subsamples of soil were made at a depth of 0-20 cm, the samples were placed to dry in paper bags in the air and then to the central laboratory of the University Chapingo were sent, where did determinations hydrogen potential (pH), organic matter (MO), electrical conductivity (CE), nitrogen (N), phosphorus (P) and potassium (K).

Laboratory analysis to fertilizer used in 2011, in order to determine whether the application of organic fertilizers using crops grown locally and affect soil properties and fertility was also performed.

Results and discussion

The agricultural (annual crops), evergreen (fruit trees and shrubs) and livestock (animals): three types of components were identified. This would be agroforestry is agrosilvicultural system and the technology used is trees in alleys.

We found a wide range of orchards in Tlaxcala, there are medicinal or ornamental plants located in a corner of the house, to commercial farming. However, showing greater adaptability, according to ^{González (2003)}, it is combining fruit and shade trees with other plants which may include cereals, grasses, legumes and are designed for both home consumption and for the market, peasant you can modify crop plants quickly, without changing the structure of the system.

The interactions of annual and perennial crops component are as follows: are in the same space and although you might think that there is competition for nutrients and sunlight because it is no arrangement between them. To begin, the terrain is pending. A measure taken to prevent soil loss by wind or water erosion was soil conservation through terracing level, using the apparatus A.

In the levees fruit trees such as pear, peach and plum serve as mulch to protect the soil they were planted also provide organic matter because they are deciduous trees, ie, in winter drop their leaves and annual crops to be near trees, receive a portion of organic matter. Another benefit is that by having a taproot not compete for nutrients since absorbed into deeper soil layers.

The interaction of livestock with annual crops component helps control pests, because chickens eat grasshoppers. The horses are used to the team, this helps to reduce soil compaction and manure obtained is used for the production of organic fertilizers which are applied to annual crops and fruit trees.

In the particular case of this research, the agroforestry system to which the study unit belongs classified as trees in farmland, which is considered as an alternative to the deterioration of natural resources and serves to adopt new techniques and management practices allowing its use and persistence (^{Magdaleno et al., 2005}).

Regarding agricultural component inputs during the two years that conducted the research took into account the crops grown on each terrace and these were classified in cereals, legumes and vegetables. It planted to know the proportion of crop area was also calculated. In the case of the outputs were yields and total crop production in the plot. It should be noted that the seeds of annual crops comes from previous crops or are obtained in the same community.

It was observed that the yields in the 2011 cycle were: white corn 894.64 kg ha^-1, beans 818.86 kg ha^-1 and beans ayocote 818.86 kg ha^-1. Low yields of the three crops were due to the rains did not come in the right season and the presence of frost since September, also had a strong attack of pests. In the case of maize was that of grubs which reduced its production, but the bean had a yield of 3 787.57 kg ha-1 as it has resistance to frost and pests did not affect production.

The database Agricultural Information System Consultation (SIACON), average crop yields during the spring-summer temporary state of Tlaxcala cycle was reviewed and compared with the yields obtained in the study plot (Table 2).

Table 2 Average yield in Tlaxcala during the spring-summer temporary. 

It can be observed that the performance of the plot was lower for white maize, and in the case of forage oat yield obtained increased by 132.02%, the same thing happened to the bean where performance in the plot increased by 389.35%.

In 2012 white maize yield was 1 765.5 kg ha-1 and bean 1 477.2 kg ha-1. This was because the rainy season was more abundant and the presence of pests was minimal, however in the case of tomato itself was the presence of diseases and pests, such as fleahopper, but allowed products were applied in organic production (tricarboxilos vegetables and adherents) to control the attack, which helped to improve performance.

The yield for white maize increased by 97.34% and bean 80.39% compared to 2011, this was due to the rains were distributed more evenly in 2012, starting from early may to rain, also to the incidence of pests in maize was minimal in 2012 which optimized production and grain quality.

In the Table 3 comparison state yields Tlaxcala of SIACON (²⁰¹⁰) with those obtained in the plot in 2012. In the case of white maize was this an increase of 7.65% is made while the blue corn had decreased; bean increased yield and decreased tomato 70.47%.

As can be seen, in some cases yields were low; however, the intake of carbohydrates and protein was enough for a family of four.

Table 3 Performance comparison of 2011 and 2012. 

Estimation of carbohydrates and proteins in the plot

The production obtained in each crop year and the boards of the National Institute of Nutrition (INN) were used to determine the concentration culture was used to estimate the intake of carbohydrates and proteins; by rule of three input shown in Table 4, where it can be noticed that the total sum obtained by the crops produced in 2011 was 491 kg and 133 kg carbohydrate protein was obtained.

Table 4 Contribution of carbohydrates and proteins 2011. 

In the Table 5 shows that in 2012 the contribution of carbohydrates and protein increased compared to 2011, this is because the production was better in 2012 so the carbohydrate intake was 1 062 kg and the 326 kg protein.

Table 5 Contribution of carbohydrates and proteins 2012. 

Once the total amount of carbohydrates and protein in the plot was investigated what the nutritional requirements that need carbohydrate and protein a person per day, which is 330 g of carbohydrates and 82.5 g protein; this figure wasextrapolated to a year to meet the annual contribution per person, and to know how many people meet their nutritional needs total carbohydrate and protein intake that occurred in each year of carbohydrates and protein requirement was divided between.

In 2011 it was possible to meet up to four people, while in 2012 to eight in carbohydrates and protein 11. The increase from one year to another is a reflection of increased production in 2011 and 2012.

The average size of a family in the community of Vicente Guerrero according to the census of 2010 is four, therefore the requirements in two years that quantified the contributions of carbohydrates and proteins are completely covered for a family, and that is, family organic agroforestry system covers one hectare nutritional needs and contributes to food sovereignty.

Conclusions

The organic agroforestry system is located within the system "trees on arable land" has three types of components: annual crops, perennial crops and animals, where interactions between oats as fodder for animals, agricultural products such as corn, beans are presented, beans, vegetables and fruit for their own consumption, and vegetables and fruit for sale.

The proportion of crops in 2011 was 48% for cereals (maize and oats), 42% legumes (beans and bean) and 10% for vegetables and fruit, while in 2012 the area was used by 41% for corn, 28% for beans and 31% for vegetables and fruit.

The family organic agroforestry system of one hectare in 2011 had total carbohydrate intake of 491.08 kg and 133.086 kg of protein able to provide carbohydrates and proteins 4.07 people to 4.45. In 2012 total contributions 1 062.26 kg of carbohydrate and 326.87 kg of protein were obtained to provide 8.81 people carbohydrates and the proteins 10.85.

In the soil will they could notice changes in pH, MO, N, P and K before and after planting. The pH was decreasing as the K, due to increased precipitation in the second year of observation and absorption of nutrients by the crops. The N and P were higher soil before planting and then decreased due to the extraction of crops.