Cover Image
close this bookSustainable Management of Soil Resources in the Humid Tropics (UNU, 1995, 146 pages)
close this folderVIII. Nutrient management
close this folderB. Reducing nutrient losses
View the document(introductory text...)
View the document1. Soil erosion
View the document2. Leaching
View the document3. Volatilization losses

3. Volatilization losses

High soil temperatures and moist conditions throughout the year may accentuate volatilization loss of nitrogen contained in the soil and applied in fertilizers and organic amendments. Soil temperatures of 40° to 50°C at 1 cm depth are commonly observed. Several soil and fertilizer management options are available that can decrease volatilization losses. Use of crop residue mulch and no-till systems are useful techniques to regulate soil moisture and temperature regimes. Maintaining continuous ground cover through mixed and relay cropping is another useful strategy. Volatilization losses can also be reduced by the incorporation of fertilizers and organic amendments into the soil rather than broadcast on the soil surface.

There are fertilizer formulations that are less soluble and decrease volatilization losses. Coating nitrogenous fertilizer with material that decreases solubility also decreases volatilization losses. The slow release formulations are effective in reducing losses due to leaching and volatilization. The use of nitrification-inhibiting compounds is another strategy to inhibit oxidation of ammonia into nitrates. These compounds are usually applied at low rates of 0.5 to 1.0 kg/ha.

Weed Control: Effective weed control can be achieved through appropriate measures of soil and crop management. Although weeds compete for limited resources, nutrients absorbed by weeds are temporarily immobilized and remain within the ecosystem. Judicious weed control can be achieved through crop management, soil management and application of herbicides. The soil and crop management techniques of weed control are more appropriate than chemical control measures for resource-poor farmers.

Table 30 Tropical legumes that can be grown as cover crops to procure in situ mulch

Common name

Scientific name

Calopo

Calopogonium mucunoides

Centro

Centrosema pubescens

Glycine (perennial soybean)

Glycine wighrii

Huban clover

Arachis prostrata

Kudzu

Pueraria phaseoloides

Mucuna

Mucuna utilis

Phasey bean

Phaseolus lathyroides

Pigeon pea

Cajanus cajan

Psophocarpus

Psophocarpus palustris

San hemp

Crotalaria juncea

Spanish clover

Desmodium ucinatum

Stylo

Stylosanthes gracilis

Townsville stylo

Stylosanthey humilis

Velvet bean

Stizolobium deeringianum

Nutrient contents (%)


N

P

K

Calopogonium spp..

3.02



Desmodium trifolium

2.93

0.14

1 30

Mucuna sp..

2.96

0.32

1.57

Pueraria spp.

2.38

0.25

2 30

(Adapted from Lal. 1990c.-FAO, 1990)