**Soil Acidity and Liming in Tropical Fruit Orchards**

William Natale, Danilo Eduardo Rozane, Serge-Étienne Parent and Léon Etienne Parent

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/53345

**1. Introduction**

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In Brazil, agribusiness generates some US\$ 330 billion in revenue per year and is the most important sector of country's economy, accounting for 30% of GDP, 36% of exports and 37% of the jobs. This activity is one of the main reasons for Brazil's trade surplus in recent years, with annual farm exports worth more than US\$ 60 billion [1].

Based on these figures, it is no exaggeration to say that more than one-third of the Brazilian annual wealth is supported by a single natural resource: the soil. This justifies the impor‐ tance of studies on how to preserve and improve this valuable resource. According to [2], soils have natural limits to their ability to nourish plants and sustain crop productivity. The degradation of soil quality reduces this ability and at the same time deteriorates the quality of water for various uses. It is senseless to claim that agricultural technology can compen‐ sate for poor soil management.

Fruit growing is an important component of Brazilian agriculture, occupying 2.3 million hectares and producing 41 million metric tons of fruit annually, totalling some US\$ 10 bil‐ lions. This ranks Brazil among the world's leading fruit producers [3]. Despite this standout position, fruit yield remains unsatisfactory compared to many other countries. Among fac‐ tors contributing to this situation, perhaps the most important is the deficient use of techni‐ ques to manage soils, crops and the environment.

Because of advances in genetic improvement in recent decades, plants now produce more yields of higher-quality fruits, but the demand for and the export of nutrients, as can be ex‐ pected, are also higher. On the other hand, Brazilian soils tend to be naturally acic and low in fertility and/or are subjected to overexploitation, leading to exhaustion. Soil acidity is one of the main factors that reduce crop yields as in other tropical regions of the globe. Liming is a widely used technique in annual cropping systems but for perennials such as fruit trees,

liming is more complicated due to the characteristics of these plants and the lack of scientific knowledge on this subject. Fruit trees, like all other perennials, keep producing for many years in practically the same volume of soil, which is the reason why soil acidity requires special attention. Despite the high importance of lime application for most fruit trees, there is a lack of information on the effects of this soil treatment technique during the planting, formation and production stages of orchards.

The application of limestone on annual crops, with homogeneous incorporation in the soil, is a common practice, although not recognized as it should be. In perennial crops, the incor‐ poration of limestone ismore complex due to the intrinsic characteristics of these plants and the lack of scientific and technological information [9]. This is the case, for example, for the

Soil Acidity and Liming in Tropical Fruit Orchards

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In acid soils with high aluminum saturation, liming promotes the neutralization of the toxic Al in the surface layers, hence enabling more intense proliferation of roots with positive ef‐ fect on plant growth. However, it is important to consider the need to incorporate the lime‐ stone thoroughly into the soil at the time of planting perennial crops because surface application alone acts slowly on the deeper soil layers and a soil insufficiently corrected at the establishment of the orchard can impair crop productivity for a long time [10]. The ho‐ mogeneous incorporation of limestone allows greater contact between the amendment and the sources of acidity, speeding up the corrective effects that support efficient use of water

The importance of the root system is obvious because there is a close dependency between root development and the aboveground portion of the plant. The greater or lesser success of applying limestone and fertilizers, in turn, depends on the nature of the root system and on the volume of the soil effectively exploited by the particular plant species. Correction of acidity is the most efficient way to eliminate chemical barriers to the full development of the

Unlike other agricultural inputs such as fertilizers, herbicides and insecticides, limestone can be considered an investment, because its benefits last over more than one harvest. This is due to the low solubility of the common limestones and the variability of particle sizes in crushed limestone, giving them different capacities to neutralize acidity over time. There‐ fore, two factors should be considered: the rate at which the acidity is corrected and the du‐ ration of the effects of liming. Fine particles promote rapid acidity correction, but this effect declines more quickly due to their faster solubilization. Therefore, the most efficient liming involves application of material with varied grain sizes to promote fast initial acidity correc‐ tion with sufficient residual effect as well. The Brazilian law (2006) states that the reactivity of liming materials after a period of three months following soil application is zero for large particles more than 2 mm in diameter, 20% for particles in the range of 0.84 and 2 mm in diameter, 60% for particles from 0.30 to 0.84 mm in diameter, and 100% for fine particle less

Because of the residual effect of limestone, liming materials applied to the soil at the time of planting orchard seedlings can keep the soil within acceptable acidity range for a certain pe‐ riod of time. However, determining the duration and intensity of the residual effect of lim‐ ing at the moment of planting fruit orchards has not been widely studied, both due to

Based on the above aspects, the best approach for liming is to apply limestone with larger grain size at the time of planting fruit orchards, with homogeneous incorporation in the soil, to prolong the residual effect, followed by use of fine material on adult trees, limited to the

experimental constraints and the time necessary to obtain satisfactory results [11-13].

majority of fruit crops in Brazil.

and nutrients by the plant in the amended layer.

roots, and consequently, of the plant.

than 0.30 mm.

Therefore, it is important to study the effects on orchards of soil acidity correction, espe‐ cially through liming, by monitoring soil chemistry and the response of the trees. Better knowledge in this respect can improve fruit crop productivity that translates into higher profits for farmers.
