Agriculture Reference
In-Depth Information
The depth of cultivation is another important choice. Common ploughing should not be deeper
than usuall, because of live and well structured layer of the soil (suggested 20-25 cm). Even
higher ploughing must be step-by step i.e. cm by cm. Recent research has shown that soil
organic carbon can be preserved by minimum tillage (shallow tillage, 10-15 cm deep). This also
results in minimal disturbance of soil life, particularly fauna and fungi. Many organic farmers
opt for shallow tillage, using the so-called eco-plough. After potato for winter cereals or annual
cover crops for maize, direct sowing is possible also in organic production. This has resulted
in considerable reduction in erosion and nutrient losses, and in improvement of soil structure.
However, no-till is hardly an option in organic farming, as herbicides cannot be used, and
hand-weeding and mechanical in-row hoeing are not feasible for field crops. Minimum tillage
may also result in an increased occurrence of weeds, especially hair grass (
Apera spica - venti
L.), camomile (
Chamomilla
), couch-grass (
Elytrigia repens
L.), creeping thistle (
Cirsium arvense
L.), barnyard grass (
Echinochloa crus - galli
L.), and pig-weed (
Amaranthus
L.), which thrive on
compacted soils.
The number of operations and their intervals ultimately determine weed infestation rates. To
avoid weed problems in the beginning of crop growth, soils are sometimes harrowed an extra
time before final seedbed preparation, so that weeds germinate, start to grow, but are killed
by the second harrowing. The first operation is called preparation of a 'false seedbed'. A certain
level of weed cover could be tolerated when crops are past their most sensitive stage [16], but
noxious weeds should be removed before setting seed. Too frequent tillage operations lead to
soil erosion and nutrient and carbon losses, and ultimately to poor soil structure.
Nutrition of cereals and maize
The uptake of nutrients with aboveground maize yields can reach up to 278 kg N ha
-1
, 46 kg
P ha
-1
and 171 kg K ha
-1
[17], in cereals approximately up to half of the amount. Target
fertilization rate depends on available nutrients in the soil and target yield. Target fertilization
rate depends also on climatic conditions, genotype, and production system like plant popu‐
lations [18, 19]. According to the EU regulations limited input with organic fertilizers is 170 kg
N ha
-1
as an average farm
-1
. It means that is impossible input the same levels of nutrients in
organic production comparing with conventional agriculture. Deria et al. [20] considered that
several factors causes grain yield differences (organically grown wheat was: increased at one
site by 17%; decreased at three sites by an average of 27%, and not changed at another three
sites) between the organic and conventional wheat: like lower nitrogen supply, and lower
extractable-P of the organic wheat.
Cereals absorb nutrients mainly from the upper soil layer. Their development depends on
available nutrients, especially phosphorus and nitrogen, released from organic fertilizers or
crop residues by mineralization.
Nitrogen nutrition is often not limited by the total nitrogen in soil, but by a deficiency in certain
growth stages, especially at the tillering stage and generative stages of winter cereals. Release
of mineral nitrogen is often maximal in mid summer, often resulting in too high nitrogen levels
in brewing barley, but still fairly low nitrogen (and gluten) levels in bread wheat.
