In conventional cropping systems, the potential of fertilization strategies to improve pathogen resistance of crops has not been intensively investigated and is largely replaced by application of chemical plant protection agents. On the other hand, organic farming systems strongly depend on the integration of fertilizer effects into plant protection strategies but are limited due to restrictions in use of certain fertilizers.

The focus of this project is an intermediate approach which emphasizes the adapted use of mineral fertilizers with the ability to increase disease resistance and suppress pathogens. Fertilizer placement strategies will be employed to improve fertilizer use efficiency and counteract weed development.

The project addresses various mineral nutrients and fertilizers as follows:

1. Silicon
2. Combinations of ammonium depot fertilization, plant growth promoting microorganisms and micronutrients
3. Nitrolime
4. Combination of foliar application of micronutrients, organic stress protectants and stabilized ammonium fertilization

The objective of these tests is to evaluate resource friendly farming without any chemical-synthetic plant protection by using various fertilizer systems and quantify their protection effects. These tests are accompanied by additional provisions, e.g. modified crop sequences and a canopy management starting with the sowing process. The yield effects in the systems to be tested are expected to be as high as conventional crops and in any case higher than the crops of organic farming.

The following hypotheses will be examined in detail:

• By applying the 4 prophylactic treatments stated above, the NOcsPS crop system will reduce the amount of pathogens and weed density.
• Within the NOcsPS crop system targeted treatments during infestation (i.e. applying silicon to leaves or a combination of above mentioned treatments) increase resistance against pathogens caused by fungi, bacteria and animals.
• Fertilizer variations allow yields comparable to high yields of conventional farming.
• Stated fertilizer treatments will lead to even material balances and negligible discharges into the environment.

Within an interactive work program, two PhD students will evaluate fertilizer and disease resistance effects of the addressed fertilization strategies in model experiments and field trials involving cereal, soy beans and maize. There will be a close cooperation of interdisciplinary central field trials. Additionally, exact trials on-farm will be initiated. All effects of prophylactic plant strengthening and fertilization (all variants) and direct pathogen defense are recorded and evaluated in comparison with negative and positive control treatments (mainly leaf applications of Si).

This will be achieved by establishment of a scoring system to quantify the degree of efficiency against diseases induced by fungi, bacteria, pests and development of weeds. Additionally, yield effects will be documented and successful fertilization strategies will be subjected to an economic evaluation.

In the beginning, literature reviews on

1. herbicidal and fungicidal effects of nitrolime,
2. disease resistance as affected by the form of N fertilization and
3. national and international safety and ecological risk assessment of the respective fertilizers.

Simple nutrient balances will be calculated for the cropping system trials and Nmin determinations will be conducted twice a year.