Banana Root System: towards a better understanding for its productive management

The deterioration of the banana root system and its effect on production is due to climatic, edaphic (physical and chemical) and biological factors. There are two kinds of root deterioration processes: 1) a fast one with accelerated collapse of the root system (days to months) due to site specific characteristics such as limited effective depth of soil, very high sand, gravel or clay content, high water table, and high soluble salt and sodium content; and, 2) a slow and gradual collapse which is due to the degradation of soil physical and chemical conditions, deterioration of soil biological activity, inefficient drainage (design, construction, management and maintenance) and poor crop management practices (disease control, nematodes, insects and weeds). The interaction between rainfall and topography ranks among the main climatic factors that can cause a fast or gradual collapse of the banana root system. On the other hand, corm rot (due to several causes), nematodes, and decrease in the soil biological activity are identified among the most important biological factors. The various physical, chemical and biological factors that cause deterioration of the root systems in Latin America are examined from the production point of view and experience of the authors. The application of new concepts and procedures (Soil Quality and Health) will make it possible to quantify the impact of the soil physical, chemical and biological properties in root performance and in banana production. This will also make it possible to determine, with precision, the production potential of the soils of the various banana zones and to manage them within the concepts and goals of sustainable production. The need to undertake more basic and applied research on the various factors that determine banana root performance are highlighted in order to design and implement more economically efficient production practices. Resumen La problemática del deterioro radical del banano y su impacto en la producción: Experiencia en América Latina El deterioro del sistema radical del banano y su efecto adverso en la producción se debe a factores climáticos, edáficos (físicos y químicos) y biológicos. Se presentan dos tipos de deterioro del sistema radical: 1) uno rápido con colapso acelerado del sistema radical (días a meses) debido a condiciones especificas al sitio tales como limitada profundidad efectiva del suelo, excesos de arena, grava o arcilla, nivel freático alto, y elevados contenidos de sales solubles y sodio; 2) un deterioro lento y gradual debido a la degradación paulatina de las propiedades físicas y químicas del suelo, deterioro de la actividad biológica, sistemas de drenajes deficientes (diseño, implementación, manejo y mantenimiento) y prácticas pobres de manejo del cultivo (control de enfermedades, nemátodos, insectos y malezas). Entre los factores climáticos se debe destacar la interacción de la precipitación y la topografía, la cual resulta en condiciones que pueden generar el colapso rápido o paulatino de la raíz. Por otro lado, entre los biológicos se destacan la podredumbre de los cormos (por diferentes causas), nemátodos y disminución de la actividad biológica del suelo. Las propiedades físicas, químicas y biológicas que comúnmente resultan en deterioro del sistema radical del banano en las diferentes áreas productoras de banano de América Latina son examinadas a la luz de la experiencia práctica de los autores realzando su impacto en la producción. La aplicación de nuevos conceptos y procedimientos (Calidad y Salud de Suelos) permitirán cuantificar el efecto de las propiedades físicas, químicas y biológicas del suelo en el desempeño de las raíces y en la producción. Esto también permitirá determinar con precisión el potencial productivo de los suelos de las diferentes The problem of banana root deterioration and its impact on production 14 C.A. Gauggel et al. 15 zonas bananeras y manejarlos dentro del concepto de producción sostenible. Se realza la necesidad de hacer más investigación básica y práctica en los diferentes factores que determinan el desempeño radical para poder diseñar e implementar prácticas de producción más económicamente eficientes. Introduction It can be stated without a doubt that climate and soils determine the success of banana production enterprises. In most cases, climatic factors are easier to determine; however, the soil component is much more difficult to characterize due to the variation of the soil morphological, physical and chemical properties within a given area (large or small) under the same climate. The effect on banana root performance of the various components of these two factors has not been fully understood mainly due to the interactions that occur among them. However, the effect of some soil properties on root performance has been understood to a considerable extent after the experience gained during the great expansion of the banana industry in the 1990s. From an historical point of view, the understanding of the banana soil-plant relationship can be divided into periods before and after 1990. Before 1990, the banana industry in general was very respectful of soil quality; only soils with optimum morphological, physical and chemical conditions were placed under banana production. However, after 1990 the lack of suitable soils for banana production, very high prices for the few available soils, decisions made without adequate soil studies, and dangerous speculation typical of new and unknown markets, led many investors (large and small) to develop areas with undesirable soil conditions. This resulted in deterioration of the banana root systems in those areas, some gradual and some fast. In most cases these “experiments” associated with unfavorable market conditions had disastrous consequences for many investors. However, it also generated the need to better understand the causes and interrelations of the climate-soil-root complex in banana production. The level of knowledge of such a complex problem has increased significantly in the last thirteen years as a consequence of past experiences and the advent of new and promising technologies. Thus, the objective of this paper is to undertake a general review of the production experience in Latin America as a consequence of banana root system deterioration in light of the lessons learned from the past and the opportunities offered by the future. Causes of banana root system deterioration In general, the causes of banana root system deterioration are the same as those determining yield. They can be classified as climatic, soil-related, and biological (diseases and insects affecting banana roots). The degree to which root deterioration occurs will be determined by the intensity of the predominant factors involved under the specific site conditions. In this way, the deterioration of the banana root system can be slow or fast frequently too slow to be detected immediately. Factors that cause a fast deterioration of the banana root system These factors are usually directly related to climatic conditions or soil properties and have drastic negative impacts on the banana plant. They are of major geographic importance in Latin America and strongly influence the banana root system (Table 1). The problem of banana root deterioration and its impact on production14 C.A. Gauggel et al. 15 Table 1. Important factors involved in banana root deterioration and poor development Factors Effects in the banana root system Soil factors Restricted soil effective depth Weak development of the root system, shallow and thin roots Extreme textures (massive clay, sand and burden) Weak root system, many dead roots, few live roots Poor internal soil drainage. Short, weak and rotten roots, abundant dead roots Soil compaction inherited from previous land uses Short, shallow and horizontal roots High exchangeable and soluble sodium contents Few short functional roots with frequent injuries; many dead roots High soluble salt concentrations Similar to above Climatic and topographic factors High water table Many dead roots, shallow root system Frequent water logging of the upper soil horizons Many dead roots, many accidental roots, (rain and poor surface drainage) superficiaroot system Frequent flooding Many dead and rotted roots, many adventitious roots Phytopathological factors Rotten roots Many dead roots, also corms with lesions Climate and topography Rainfall is the most important factor involved in banana root system deterioration. It interacts with topographic factors that may result in severe adverse conditions for banana root development. The most important of the possible interactions are flooding, puddles after rains, shallow water tables (permanent or frequently fluctuating), and areas too close to sea level to be effectively drained. In areas with rainy and humid climates, whose soils have high organic matter contents with high water retention, bananas generally experience root and corm rot. This results in a collapse of the plantation during the first crop and in an irreversible deterioration of the root system. Such cases are common on the Atlantic coasts of Costa Rica, Panama and Colombia (specifically the Urabá zone) in areas previously used either for pasture, secondary forest or left fallow for long periods.