Round shaped,
continuous vertical pores (CVPs) are voids in the soil created by soil
organisms including earthworms and plant roots. CVPs are preferential pathways
for root growth in the subsoil, especially when high mechanical resistance
limits root elongation through the bulk soil and can enhance air transport in
soils and water percolation, reducing the risk of water ponding or water runoff
from the surface. In
turn, water flow through CVPs was shown to increase the transport of solutes
such as nitrate, dissolved P and plant protection agents towards the ground
water body.
In
this paper, the authors hypothesized that potential effects of CVPs on shoot
growth of winter wheat (Triticum aestivum L.) increased with: 1)
decreasing availability of water and 2) decreasing availability of nutrients in
the topsoil. A multifactorial microcosm experiment was
established with two different phosphorus concentrations in the topsoil
(P+/P−), irrigation (Irr+/Irr−) and presence of continuous vertical pores in
the subsoil (CVP+/CVP−) as factors. The
experiment was conducted in PVC-pipes with an inner diameter of 19 cm and a
total height of 85 cm. 12 seeds of winter wheat (Triticum aestivum L.) “Graziaro” were
sown into each column corresponding to a seeding density of 422 grains m−2.
In total, wheat was cultivated for 16 weeks. Shoot biomass was measured as dry
matter with oven drying (65˚C). C/N and P contents of soil and plant samples
were measured using dry combustion with a Fisons NA-1500 elemental analyzer and
atomic absorption spectrometry (AAS), respectively. Leaf area index was
determined with a LI-3100 Area Meter (LI-COR Inc., USA).
The results indicated that total root length of winter wheat in 20 -
60 cm soil depth was higher when CVPs were present and the magnitude of this effect
gradually increased with increasing soil depth. Irrigation did not change root
length significantly. Total root length was generally higher throughout all
soil depths when winter wheat was cultivated in topsoil containing high
concentrations of P. And presence of CVPs generally had a positive effect on shoot dry matter and N uptake of
wheat, but the magnitude of the effect was different between treatments.
In conclusion,
increasing CVP densities by cultivating taprooted crops or promoting anecic
earthworms can be an element of strategies for soil fertility building. At the
same time, adequate nutrient supply in the topsoil is essential.
Article by Tim Dresemann, et al, from Germany.
Full access: http://mrw.so/51Sf9A
Image by Forest and Kim Starr, from Flickr-cc.
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