1. Introduction

The semiarid regions are characterized by an irregular distribution of rainfall with greater variability between years and within the same year, and high solar radiation. This hydric variability originates from complex systems of the formation of rain, with the occurrence of concentrated rain in a few months of the year and alternate years, irregularity, existence of geographic barrier concentrating higher humidity in the valleys and leaving dried slopes, and variability of soil with greater or lesser ability to retain water [1].

© The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

distribution, and eproduction in any medium, provided the original work is properly cited.

The variability of rainfall provides the diversity of fauna and flora species in the semiarid region. The soil and climate conditions are associated with the characteristics of species, such as solar radiation, sunshine, and air temperature. The climatic variations suggested that animal production systems operate according to the availability of resources and controlled principally by the availability of water, adopting rational strategies for production.

In rainfed situations where crops depend on unpredictable seasonal rains, the maximum use of soil moisture is a crucial component for drought resistance, that is, water-use efficiency allows

Ensiling of Forage Crops in Semiarid Regions http://dx.doi.org/10.5772/101990 67

Drought resistance is the ability of a plant to produce with minimal loss in a water-deficit environment. Drought resistance mechanisms can be classifieds into the following three cate-

Drought escape is the ability of plants to complete the life cycle before there is a serious water deficit for plant and soil. The phenological development of plants is fast with early flowering and maturity and the duration of the growing season depends on water deficit [6]. The success of these species depends on the efficient reproduction before a more intense water stress. With short life cycle and high growth rates and storage, this process uses reserve for seed produc-

Drought avoidance is the ability of plants to maintain some potential of water in the tissue even with low moisture in the soil. The better absorption of water, mobile water storage, and reduction of water losses are some of the processes that are used for these plants. The balance between turgor, increased depth of rooting, higher absorption efficiency, and lower losses of water allows the survival of plants under dry conditions [6]. Furthermore, older leaf senescence reduces the energy cost of the plant [7] directing all the energy to dry the adaptive

Drought tolerance is the ability of plants to resist water deficit with low potential of water in the tissues [6]. In water-limited environments, the plants can produce forage mass using water maintenance mechanisms in the plant. One of the processes is the osmotic adjustment. Osmotic adjustment is an adaptive response to cellular stress that in some cultures increases the avoidance dehydration and supports the production yield under stress [5]. Osmotic adjustment maintains turgor and resists to dehydration through solute accumulation in the cell, an

In drought, these plants maintain the water content accumulating several nontoxic solutes that do not interfere with metabolism; these are compatible solutes such as fructan, trehalose,

Although the drought resistance is important for crop production in semiarid, the adjustments resulting from this drought tolerance have disadvantages because of lower production output. The stomata closure and reduction in leaf area result in lower carbon dioxide assimilation and higher osmotic adjustments that can have a negative effect on the plant energy requirement [4]. Cultivate crops are grown using more than one mechanism to resist drought [9]. Thus, it is interesting to note that the adaptive mechanisms of crops grown in the semiarid region have a balance of escape, avoidance, and drought tolerance, maintaining the yield production as much as possible. Through conventional breeding or biotechnological methodology, the devel-

Most of the crops produced in the world are sensitive to water deficit. Even cultivative crops, such as pearl millet, sorghum, and pigeon pea, in semiarid regions are affected by drought

the production yield even in the situations of water deficit [5].

increase in cell elasticity, and a decrease in the cell size [6].

polyols, glycine, proline, betaine, and polyamines [4, 8].

opment of superior genotypes resistant to drought is possible [4].

during the reproductive stage [4].

tion [7].

mechanism.

gories: drought escape, drought avoidance, and drought tolerance [6].

In semiarid regions, annual rainfall is irregular, low, and highly variable in space and time, with permanently high evapotranspiration rate. Therefore, the agricultural systems used in the semiarid region should be based on plants that develop efficiently and quickly by using the resource availability of pulses [2], because the water dynamics is the main variable for controlling the transformation process of individual nutrients available for plants.

Tropical regions, such as semiarid regions of Brazilian, may have a high capacity for forage production, but climatic variables make it difficult for the development of the animal production system. The quantity and quality of forage are key factors for animal production. The management also influences the forage characteristics and animal production. During the dry season, a significant reduction in native vegetation occurs, and this affects animal forage production.

The shortage of forage during the dry season and low nutritive value of forage may compromise the animal production, resulting in decreased productivity. In this situation, the producers become dependent on the availability of the preserved forage, hay, and silage, cultivated forage crops, and crop residues to feed cattle in the semiarid region [3].

For the efficient production of forage in the semiarid regio, it is essential to know conditioning factors inherent to soil, climatic condition, and plant interaction mechanisms to drought and production capability. Adapted crops, due to their efficiency in the accumulation of green matter in these climatic conditions, are available as a more viable option to the semiarid region. Among other considerations. the forage conservation practices, silage is a better alternative to reduce the qualitative and quantitative fluctuations in the supply of forage to the animals.

As a literature review, this chapter presents scientific reports on ensilage of forage with productive potential for the semiarid regions. This study presents the main crops for ensilage in the semiarid regions and their fermentation characteristics.
