Fertility capability soil classification: a tool to help assess soil quality in the tropics

Abstract

The soil quality paradigm was originally developed in the temperate region with the overarching objective of approaching air quality and water quality standards. Although holistic and systemsoriented, soil quality focused principally on issues arising from large nutrient and energy inputs to agricultural lands. Soil quality in the tropics, however, focuses on three overarching concerns: food insecurity, rural poverty and ecosystem degradation. Soil science in the tropics relies heavily on quantitative attributes of soils that can be measured. The emotional, value-laden and ''measure everything'' approach proposed by some proponents of the soil quality paradigm has no place in the tropics. Soil quality in the tropics must be considered a component of an integrated natural resource management framework (INRM). Based on quantitative topsoil attributes and soil taxonomy, the fertility capability soil classification (FCC) system is probably a good starting point to approach soil quality for the tropics and is widely used. FCC does not deal with soil attributes that can change in less than 1 year, but those that are either dynamic at time scales of years or decades with management, as well as inherent ones that do not change in less than a century. FCC attributes can be positive or negative depending on the land use as well as the temporal and spatial scales in question. Version 4 is introduced in this paper. The main changes are to include the former h condition modifier (acid, but not Al-toxic) with ''no major chemical limitations'' because field experience has shown little difference between the two and to introduce a new condition modifier m that denotes organic carbon saturation deficit. Additional modifiers are needed for nutrient depletion, compaction, surface sealing and other soil biological attributes, but there is no sufficient evidence to propose robust, quantitative threshold values at this time. The authors call on those actively involved in linking these attributes with plant growth and ecosystem functions to provide additional suggestions that would enhance FCC. The use of diffuse reflectance spectroscopy (DRS) shows great potential on a wide range of tropical soils. The evolution of soil science from a qualitative art into a 0016-7061/03/$ -see front matter D

Agronomic phosphorus imbalances across the world's croplands

“…5 and Fig. S5A), such as East Africa and northern Brazil, indicating potential constraints on crop productivity other than agronomic P inputs, including fixation of applied fertilizer P to less plant-available forms in soils, deficiencies of other soil properties (28), or the lack of adequate irrigation. Relatively low agronomic P inputs may have contributed minimally to augmenting crop production in these areas compared with other areas that have low crop production.…”

Production of ornamental sunflower irrigated with oilfield produced water in the Brazilian semiarid region

“…The application of PWF may have started a salinization process, during the first production cycle, reaching EC = 3.11 dS m -1 within the upper soil layer (Table 4); however, this value did not differ from those observed in other irrigation treatments. A variation of EC between 2 and 4 dS m -1 can provide an early warning for salinization potential within the surface soil (Sanchez et al, 2003), although the saline character is considered only with changes of EC ≥4 dSm -1 .…”

Soil attributes functionality and water eutrophication in the surrounding area of Itaparica Reservoir, Brazil

“…Due to these characteristics, the pH is strongly to moderately acid (EMBRAPA, 2006) but predominantly above 5.5 in the surface horizon. This suggests that there may be no problem of aluminium toxicity for most of the crops (Sanchez et al, 2003). Concerning functionalities, these soils have very low capacity to supply nutrients to plants and hence their agricultural management is strongly dependent on the use of fertilizers.…”

“…The pH is neutral to moderately alkaline ( Figure 5A) (EMBRAPA, 2006) as a result of the exchangeable sodium percentage (Qadir et al, 2008) and also of carbonate content, with values from 5 to 16% (CHESF, 1987). Due to the above characteristics these soils may have a nutrient imbalance or deficiency, particularly of iron and manganese (Sanchez et al, 2003;Qadir et al, 2006).…”

“…However, it should be emphasized that in tropical conditions inherited properties are considered more important indicators of soil quality than in the temperate climate zone (Sanchez et al, 2003).…”