Some considerations on the flooding of agricultural soils

Dear readers, this publication arises from the climatological situation that is arising in the South Zone of Lake Maracaibo Venezuela, which for several weeks with the entry of the rains have increased considerably the rainfall in the region causing the overflows of the Zulia and Chama rivers leaving under water a large amount of cultivated areas. Although the situation has also affected the homes of many families, in this publication we will focus on some climatic aspects, consequences and possible management of these soils when the waters recede, as this has been a concern of some of the producers who have been affected by this unfortunate natural disaster.

To enter into context, it is important to mention that the Municipality of Colón in the Southern Zone of Lake Maracaibo, Venezuela, where we currently reside, has been one of the sites affected by the floods. The area has approximately 500,000 hectares, which are used for the production of agricultural products, making it an area of high national potential in the area of agri-foodstuffs. Some specialists, such as Uzcategui (2008), point out that 70% of the aforementioned area corresponds to an alluvial plain, that is, flat lands that have been progressively formed by the deposit of sediments generated by floods.

On the other hand, it should be noted that the Municipality of Colón has a warm-humid tropical climate and there are two marked periods of rainfall, approximately from the end of April to June and from mid-October to December. The soils vary in texture from loam, clayey and sandy, although generally in the production units where some experimental trials have been carried out, the soil analysis shows clay loam soils in different areas.

As you have been able to see, the surface of the area is flat and alluvial, this is not the first flooding that has occurred, for example, in 2005 and 2010 there were also overflows of the Chama River. This type of disaster is caused by excess water in the high or mountainous regions due to high rainfall, and some environmentalists point out that in the mountainous zone indiscriminate deforestation is generated, which aggravates flooding in the lower areas. To explain the problem of deforestation in the headwaters of rivers, Sánchez (2005) points out that in forested areas, the cover of plants and trees act as a sponge that does not allow water to drain easily, but rather accumulates slowly in the phreatic mantles (accumulation of water under the ground), which favors water bodies in times of drought.

Consequently, when forests are deforested, there is no absorption and the water does not go to the deep areas of the soil, which causes, especially when rainfall increases, that the water moves uncontrollably over the surface, causing serious flooding disasters, as is currently happening in the south of Lake Maracaibo. Sometimes river banks are deforested to establish agricultural systems, but from the point of view of water absorption, some researchers point out that crops such as pastures, vegetables and others, do not have the same absorption capacity as trees.

It is also important to consider the rainy season and soil variables, since we are coming out of a period of drought and entering the rainy season, the high rainfall has caused a hydrological imbalance, which is evident in the flooding of agricultural soils that mostly have a higher proportion of clays, i.e. soils that are difficult to drain, because they are very fine particles with very small pores, i.e. when the flow of water from the rivers decreases it will take a while for the water to drain.

Excess water in heavy soils generates lack of aeration and nutrient washing, i.e. they are highly compromised, if excess water persists, the lack of aeration will cause a significant decrease of functional microorganisms present in the soil, it can also generate anoxia in the roots of crops stopping their growth and of course the loss of some nutrients will affect the yield of some crops when water decreases.

When water decreases, what can be done with soils?This is the question that many people ask themselves and we will give our opinion focused on pasture crops. First of all, make a diagnosis and verify the conditions of the pastures, then the ideal would be to carry out a soil sampling to show some of its characteristics such as pH. To correct pH problems, some amendments can be applied for acidity, such as agricultural lime, and for alkalinity, organic fertilizers or nitrogen fertilizers can be applied.

The application of organic fertilizers with a high load of microorganisms can help a lot, since the river drags sediments and organic matter, apart from that, in the soil due to the lack of aeration the edaphic biota decreases, when we apply fertilizers we are providing the soil with a high microbial load complementing the possible existing deficiency, these will have the function of decomposing the organic matter present and supplying nutrients. Nitrogen fertilizers can also be applied to keep the microbial activity active and supply the grass with this element, which is essential for its growth.

Dear readers, after the floods, the surfaces that maintain pastures should be fertilized and fertilized as mentioned above to revive these plants, in case there are still high levels of humidity do not introduce animals, because it could generate a soil compaction, by the pressure they make with their paws. These measures will allow the grassland ecosystem to recover progressively; if there is degradation in some areas, they should be replanted.

- Uzcategui, A. (2008). Venas del Sur del Lago, Caminos de agua. 2 ed. Universidad de los Andes, Faculty of Forestry Sciences.

- Sánchez, L. (2005). Deforestation of forests aggravates floods. Universidad Veracruzana. Mexico