Measurement of soil redox potential The most frequently occurring redox species in the soil N S Fe Mn Aerated soil : oxidative conditions Soil covered with water: reductive condition

Measurement of soil redox potential Related to the concentration of oxidized and reduced substances suitable for characterizing the extent of reducing (or oxidizing) nature of the medium (-0.35V - 0.8V) Why is long-term reducing condition harmful?

Movement of nutrients into the soil in the root surface Movement of nutrients in the root surface Movement of nutrients into the soil in the root surface interception mass flow diffusion

Movement of nutrients into the root surface

The ratio of cations Antagonism, Ehrenberg law Ideal soil: Ca: 65-80% H: max 10% K:4-8% Mg: 15-25% Na: max 1%

nutrient uptake through leaves through stomata Or by active transport

Plant nutrient uptake CO2

Relationship between nutrient supply and the yield Liebig law Plant growth is determined by the minimum nutrient available to it. If one growth factor is limited plant growth is also limited, even if all other Nutrients are Adequate of As the capacity of the barrel is limited by the shortest stave

Mitscherlich law yield Nutrient supply

Mitscherlich law (diminishing response curve) yield Fertilizer Doses with successive applications of fertilizers the yield increments become progressively smaller.

The effect of nutrient supplyon the quality of the crop HoHow can quality can be characterized? The effect of : N P, K, B

N in soil total N: 0.02-0.4 % N forms in the soil, there ratio N forms available for plants

N in soil soil enrichment processes: N fixation fertilization Sources and losses (Fig on the board) soil enrichment processes: N fixation fertilization organic manures lightning symbiotic bacteria (legumes) nad non- symbiotic what is symbiosis

N in the soil (sources of loss) . Maize yields for example: approx. 8 tons / ha

N in the soil (sources of loss) The concept denitrification rate of denitrification loss

N in the soil (sources of loss) Nitrate leaching depends on: season soil texture leaching rate (20-50kg / ha) ammonia volatilization fixation

N in the soil, N turnover conversion of organic nitrogen forms to inorganic forms Aminization, ammonification, nitrification conversion of organic compounds to inorganic N forms Immobilization C/N ratio

Fertilizers, plants and animals residues denitrification N fixation using microorganisms NO3- nitrification NH4+ ( bacteria)