Reseeding and Rehabilitation

Environmental Issues In arid zones, rangeland degradation by overgrazing or continuous cropping leads to large denuded areas subject to wind and water erosion and finally lost for grazing or for cropping. These denuded areas often end up with a poor vegetation cover and a low seed bank in the soil. The topsoil is often crusted rendering subsequent water infiltration difficult. The seed bank tends to decrease continuously season after season as the soil water budget does not allows a successful germination and a proper after-growth because of low water storage. The young seedlings established by classical reseeding techniques does not survive well the drought spells. Simple low cost-low input micro-water harvesting techniques are available to stop this vicious circle and trigger a biological rehabilitation of degraded arid areas. | Environmental Issues Objectives Techniques Costs Targeted Livestock System Impact Context of Application Monitoring: EIA, Indicators References

Objective

Induce range rehabilitation and increase vegetation cover by introducing appropriate range species in combination with micro water-harvesting and seeding techniques.

Techniques

The machines available are the Pitting Machine and the Land Imprinter. These machines are old ideas based on the simple principle of water harvesting in micro-depressions, favouring the collection of water, organic matter, seeds, soil particles in shallow pits or grooves, facilitating the seedlings establishment in arid environment.

The pitting machine (Gintzburger and Skinner, 1985) is a simple modified disc plough equipped with a large seed box driven by the disc. The rolling disc(s) of the pitting machine scoop(s) a string of discontinued pits (100-120 cm long x 10-15 cm wide x 5-10cm deep) in the soil, allowing water and soil particles to accumulate in the pit. Seeds are synchronically dropped from the seed box into the pit while the machine is moving. The pitting machine is towed behind a simple vehicle and does not require heavy power or hydraulics. The pitting machine can be used on heavy clay or loamy soils.

Simple Pitting Machine for range reseeding: the Camel Pitter (from Kimberly Seeds) | This is how the pits look after rain on the Syrian Steppe
(click on photos for an enlarged view) |

The "Land Imprinter" is a heavy roller (2-3 tones) which surface is transversally grooved with corner iron. It imprints alternate 100 cm long grooves, 7-8 cm wide and 3-6 cm deep depending upon soil humidity. Seeds are dropped in front (when the soil is dry) or behind (when the soil is wet) the grooved roller. The advantage of this machine over the pitting machine is that it does not destroy the native vegetation as it rolls ever the remaining vegetation. The "Land imprinter" is towed behind a small 40-65 HP tractor. The land imprinter is mostly used on light soils, mostly wet sandy-loam or loamy soils.

Land Imprinter. This version is 3.2 tons (click on photo for an enlarged view) |

Both machines are designed to roll over obstacles (stones or small tree stumps) without damage.

Seed germination, seedling emergence and survival is enhanced if slightly covered with a few branches or if a light chain is dragged behind both machines during seeding operations. The reseeding operation is better performed just before or during the rainy season.

As the idea is to trigger a biological revival and a plant re-colonization process, the operation usually covers only 10-20% of the degraded area (and should therefore be combined with protection from excessive grazing). The reduced area does reduce the operating costs.

The Pitting machine is available from Kimseed Ltd® (<reception@kimseed.com.au>), Australia under the commercial name of the "Camel Pitter" with 2 or 4 discs equipped with individual seed boxes. The "Land imprinter" machine is not available on a commercial scale but both machines can be easily built in a local workshop for a less than one thousand US dollars each.

Costs

- The cost involved is mostly the cost of the appropriate range seeds.
- Operating the machine is a two-men operation. The pitting machine may be operated at 3-5 km/hour behind an ordinary car, not necessarily a 4 wheel-drive vehicle depending upon the roughness of the terrain. As expected, the land imprinter is slower to operate.

Targeted Livestock Systems

- Agro-pastoral and pastoral systems in semi-arid and arid tropical and Mediterranean environment.
- All arid rangeland degraded by overgrazing or opportunistic cultivation.

Grazing System

LGA | LGS1 | LGS2 | LGS3 | LGH1 | LGH2 | LGH3 | LGT1 | LGT2 | LGT3
Y | Y | Y | Y | Y | Y | Y | Y | Y | Y

Mixed System

MCG | MCR | MCC | MFF | MEF
N | N | N | N | N

Industrial System

IFP | IPL | IPG | IRM | IDU | ISL | ITN | IMP
N | N | N | N | N | N | N | N

Impact

- Positive environmental impact

- Improve water infiltration in the soil.
- Increase soil surface roughness and may decrease wind erosion when low speed wind occur.
- Reduce water erosion when harvesting excess water.
- Maintain most of the native vegetation in place.
- Increase biological diversity.
- Improve soil fertility (more organic matter accumulated).
- Increase CO2 fixation on rangeland.

- Negative environmental impact

- The land imprinter may initially slightly compact the soil in the groove if the soil is too loamy or contain clay.
- The pitting may initially start some slight wind erosion because of soil disturbance if strong wind occur after pitting is performed and before the first rain.

- Impact on livestock production
Better forage and pasture offer after plant establishment.

Context of Application

- Favorable factors

- Flat low lying areas receiving runoff.
- Overgrazed rangeland.
- Cropping areas in marginal zones receiving low rainfall.
- Private land tenure.
- Common or tribal land under strict community or government control.

- Unfavorable factors

- Underlying hard crust.
- High percentage of rocks, stones cover or tall bushes.
- Heavy clay.
- Salty crust and flats.

Monitoring: EIA, Indicators

- Fauna and flora biodiversity.
- Vegetation cover with plant intercept.
- Plant biomass measurement.
- Organic matter accumulated in pits or grooves.
- Number of livestock heads on the rehabilitated areas.

References

Gintzburger G. & P. Skinner. 1985. A simple single disc pitting and seeding machine for rangeland revegetation. Australian Rangeland Journal. 7(1): 29-31.

Gintzburger G., 1987. The effect of soil pitting on establishment and growth of annual Medicago spp. on degraded rangeland in Western Australia. Australian Rangeland Journal. 9(1): 49-52.

Kimseed. http://www.kimseed.com.au

> > [Livestock & Environment Toolbox Home]