The soil biota benefits soil productivity and contributes to the sustainable function of all ecosystems. The cycling of nutrients is a critical function that is essential to life on earth. Earthworms (EWs) are a major component of soil fauna communities in most ecosystems and comprise a large proportion of macrofauna biomass. Their activity is beneficial because it can enhance soil nutrient cycling through the rapid incorporation of detritus into mineral soils. In addition to this mixing effect, mucus production associated with water excretion in earthworm guts also enhances the activity of other beneficial soil microorganisms. This is followed by the production of organic matter. So, in the short term, a more significant effect is the concentration of large quantities of nutrients (N, P, K, and Ca) that are easily assimilable by plants in fresh cast depositions. In addition, earthworms seem to accelerate the mineralization as well as the turnover of soil organic matter. Earthworms are known also to increase nitrogen mineralization, through direct and indirect effects on the microbial community. The increased transfer of organic C and N into soil aggregates indicates the potential for earthworms to facilitate soil organic matter stabilization and accumulation in agricultural systems, and that their influence depends greatly on differences in land management practices. This paper summarises information on published data on the described subjects.
Protection of the soil habitat is the first step towards sustainable management of its biological properties that determine long-term quality and productivity. It is generally accepted that soil biota benefits soil productivity but very little is known about the organisms that live in the soil and the functioning of the soil ecosystem. The role of earthworms (EWs) in soil fertility is known since 1881, when Darwin (1809–1882) published his last scientific book entitled “The formation of vegetable mould through the action of worms with observations on their habits.’’ Since then, several studies have been undertaken to highlight the soil organisms contribution to the sustainable function of all ecosystems [
Some properties of casts of
Soil without litter | Soil with litter | |||
Surface soil | Worm cast | Surface soil | Worm cast | |
pH | 5.65 | 7.70 | 6.25 | 6.30 |
Organic Carbon (%) | 1.52 | 1.70 | 2.66 | 3.36 |
Available P2O5 (mg 100 g-1) | 0.15 | 0.24 | 0.19 | 0.22 |
Available K2O (mg 100 g-1) | 3.31 | 4.78 | 5.98 | 7.36 |
The effects of EWs on soil biological processes and fertility level differ in ecological categories [
Effect of land conversion and management practices on changes in functional catagories of earthworms in the Indo-Gangetic plains, (
Sites | Density | Biomass ( | Density ( | Biomass ( |
---|---|---|---|---|
Primary forest | 141 ( | 123 ( | 2127 ( | 2255.8 ( |
Productive agroecosystem | 1141 ( | 1323 ( | 275 ( | 2157.5 ( |
Low productive agroecosystem | 1106 ( | 1318 ( | 245 ( | 294.5 ( |
Agriculture fallow | 164 ( | 142 ( | 2274 ( | 2518.7 ( |
Sodic ecosystems | 0 | 0 | 0 | 0 |
5-year-old reclaimed agroecosystem | 0 | 0 | 143 ( | 114.4 ( |
10-year-old reclaimed agroecosystem | 0 | 0 | 282 ( | 160.6 ( |
144( | 1132 ( | 2133 ( | 2279.3( |
Values followed by the different superscript letters are significantly different in different sampling sites. Values followed by different subscript numbers are significantly different in same sampling sites [
EWs influence the supply of nutrients through their tissues but largely through their burrowing activities; they produce aggregates and pores (i.e., biostructures) in the soil and/or on the soil surface, thus affecting its physical properties, nutrient cycling, and plant growth [
Variation in nutrient concentration of earthworm casts and noningested soils during cropping under shifting agriculture in North East India (
5-year-cycle | 15-year-cycle | |||
Soil | Worm cast | Soil | Worm cast | |
Organic Carbon (%) | 2 ( |
*2.5 ( | 3.2 ( | **4.5 ( |
Total Nitrogen (%) | 0.22 ( |
*0.29 ( | 0.4 ( |
*0.6 ( |
Available Phosphorus (mg/100 g) | 0.9 ( |
*1.4 ( | 2.0 ( | **2.8 ( |
Potassium (meq/100 g) | 0.5 ( | 0.54 ( | 1.2 ( |
*2.0 ( |
Calcium (meq/100 g) | 0.9 ( |
*1.2 ( | 1.5 ( | **2.5 ( |
Magnesium (meq/100 g) | 1.2 ( |
*1.8 ( | 3.1 ( |
*4.0 ( |
*
Variation in nutrient concentration of earthworm casts and non ingested soils in abandoned agricultural fallows in North East India (
5-years-old fallow | 10-years-old fallow | 15-years-old fallow | ||||
Soil | Worm cast | Soil | Worm cast | Soil | Worm cast | |
Organic Carbon (%) | 1.2 ( |
*3.5 ( | 1.9 ( | **4 ( | 2.2 ( | **5.2 ( |
Total Nitrogen (%) | 0.22 ( |
*0.55 ( | 0.25 ( | **0.59 ( | 0.21 ( |
*0.62 ( |
Available Phosphorus (mg/100 g) | 0.38 ( |
*1.1 ( | 0.5 ( | **1.8 ( | 0.54 ( |
*1.7 ( |
Potassium (meq/100g) | 0.24 ( |
*0.61 ( | 0.4 ( |
*1.0 ( | 0.42 ( |
*0.90 ( |
Calcium (meq/100 g) | 0.19 ( |
*0.60 ( | 0.22 ( | **0.75 ( | 0.22 ( |
*0.85 ( |
Magnesium (meq/100 g) | 0.22 ( |
*0.50 ( | 0.2 5 ( |
*0.60 ( | 0.32 ( |
*0.70 ( |
*
C and N contents and C : N ratio in particle-size organic fractions in control soil and cast of
Particle size ( | Laguna Verde | La Mancha | ||
---|---|---|---|---|
C(mg g-1 soil) | Soil | Casts | Soil | Casts |
32.8 | 51.2 | 13.8 | 7.1 | |
48.8 | 54.1 | 1.6 | 1.5 | |
48.5 | 63.4 | 21.9 | 17.1 | |
50 | 22.4 | 15.2 | 29.5 | |
N(mg g-1 soil) | ||||
4.72 | 4.35 | |||
4.35 | 5.24 | 0.21 | 2.2 | |
4.06 | 5.04 | 1.91 | 2.4 | |
4.20 | 4.76 | 2.46 | 2.8 | |
C : N ratio | ||||
8.8 | 11.8 | |||
10.8 | 10.3 | 7.6 | 6.8 | |
12.0 | 12.6 | 11.5 | 7.1 | |
11.9 | 4.7 | 6.2 | 10.5 |
EWs are known also to increase nitrogen mineralization, through direct and indirect effects on the microbial community (Table
Total and mineral nitrogen content in soil and fresh casts from earthworms incubated in different soil types (Barois et al., 1992 [
Soil type | Layer (cm) | Earthworm species | Soil | Worm cast | ||
N total (%) | Mineral N ( | N total (%) | Mineral N ( | |||
Andisol, Martinique | 0–10 | Pontoscolex corethrurus | 15.5 | 516.8 | 15.7 | 1095.1 |
Andisol, Mexico | 0–10 | Pontoscolex corethrurus | 4.8 | 55.4 | 4.9 | 625.1 |
Luvic, Cuba | 0–10 | Onychochaeta elegans | 2.6 | 55.4 | 2.4 | 212.5 |
Ultisol, Yurimaguas | 0–10 | Pontoscolex corethrurus | 1.37 | 30 | 1.47 | 150.5 |
Vertisol, Lamto | 0–10 | Protozapotecia australis | 3 | 52.1 | 4 | 560.9 |
Nitrogen input/output budget during the cropping phase under 5- and 15-year Jhum cycle, (
Nitrogen balance (kg ha-1 yr-1) in different shifting agriculture cycles | ||
5-years | 15-years | |
INPUT | ||
27.60 ( | 51.4 ( | |
14.0 ( | — | |
0.80 ( | — | |
0.42 ( | 0.9 ( | |
2.85 ( | 0.7 ( | |
4.20 ( | 4.2 ( | |
Input subtotal | ||
27.0 ( | 65.6 ( | |
9.5 ( | 12.1 ( | |
75.9 ( | 95.3 ( | |
Input total | ||
OUTPUT | ||
277.6 ( | 657.9 ( | |
158.0 ( | 116.0 ( | |
1.0 ( | 1.2 ( | |
7.3 ( | 14.0 ( | |
14.25 ( | 3.33 ( | |
15.24 ( | 43.52 ( | |
Output total | ||
Input-Output difference |
Most of the studies conducted to assess the role of earthworm casting in nutrient cycling and soil structure are related to surface casting species, and only a few have dealt with casts deposited under field conditions [
Considering the potential contribution of EWs to soil fertility management, there is the need to consider them in agroecosystem management decisions. The EWs can specifically affect soil fertility that may be of great importance to increase sustainable land use in naturally degraded ecosystems as well as agroecosystems. Proper earthworm management may sustain crop yields whilst fertilizer inputs could be reduced. Since farming can involve many soil disturbing activities, the understanding of the biology and ecology of EWs will help devise management strategies that may impact soil biota and crop performance.
earthworm
soil organic matter.
The authors thank Miss Rajani for laboratory assistance and Mr. Navin for logistic support.