Potential and Limits of Pesticide Free Apple Growing by a Self-Regulating Orchard Set-Up: Project Presentation and First Experiences

Different research groups have already proven that flowering plants in orchards can enhance beneficial arthropods. Even within the tree rows different beneficial can be supported by selected plant species. In most experimental work done to stabilize the apple production system only single interaction effects were tested. However until now, no research group has quantified the additive effects of multiple measures on systembiodiversity and on the production economy. Our experiment combines all known measures of indirect pest and disease control measures in a near-to practical production model orchard without the use of any pesticide (not even organic ones). The orchard is split in 4 blocks: in two of them bio-control measures e.g. application of Granulosis Virus against codling moth (C. Pomonella) are applied; in the other two blocks no bio-control is applied. Standard commercial organic and integrated orchards with the disease-susceptible cultivar Gala in the vicinity of the model orchard are assessed by the same methods and serve as reference. Our intermediate results reveal that the self-regulating orchard developed already in the 2nd and 3rd leaf a clearly higher flora and fauna biodiversity compared to the reference orchards. The same happened in relation to the specific fruit beneficial e.g. the populations of aphid predators. In the self-regulating orchard they were capable to keep the aphid damages – in particular of the powdery apple aphid (D. plantaginea) - on trees and fruits under a commercially relevant level although the initial abundance of aphid colonies in spring was by far over the common threshold value. It is planned to continue the experiment until 2016

New insights in below ground nitrogen of clover-grass mixtures

Estimates of symbiotic nitrogen fixation (SNF) of clover in mixtures usually consider only aboveground clover nitrogen (N). However, belowground inputs of clover N derived from SNF via roots and rhizodeposition and its transfer to associated grass may contribute significantly to the amount of symbiotically fixed clover N. A microplot study with a red clover ( L.)-perennial ryegrass ( L.) model mixture was conducted within zero fertilised, bio-organic and conventional field plots of the DOK (bio-Dynamic, bio-Organic, Konventionell) long-term experiment during two consecutive years

Nitrogen Budgets and Soil Nitrogen Stocks of Organic and Conventional Cropping Systems: Trade-Off between Efficiency and Sustainability of Nitrogen Use

Organic and conventional cropping systems differ in the nature and amounts of nitrogen (N) inputs, which may affect efficiency and sustainability of N use. In the DOK (bio-Dynamic, bio-Organic, Konventionell) field experiment, organic and conventional cropping systems have been compared since 1978 at two fertilization levels. Nitrogen inputs via manure and/or mineral fertilizers, and N exports from plots with harvested products have throughout been recorded. For all treatments, N outputs with harvests have exceeded the inputs with fertilizers. Over the past years, symbiotic N2 fixation by soybean and clover grown in the trial has additionally been assessed, indicating average annual inputs of about 100 kg ha-1 yr-1 of N fixed from the atmosphere. Soil surface budgets opposing N inputs via fertilization, symbiotic fixation, seeds and deposition to N outputs via harvested products have been computed at the plot level for the duration from 1985 to 2012. The resulting balances range from negative values of about -20 kg N ha-1 yr-1 (where outputs exceed the sum of said N inputs) to surpluses of about +50 kg N ha-1 yr-1. The budget based N use efficiency (NUE; N output via harvested products divided by sum of N inputs) in the case of negative balances suggests irrationally high NUE (>100%), while positive balances are related to lower NUE for treatments with inputs exceeding outputs. Negative balances, however, indicate soil N mining, while surpluses point to a risk of N losses, and/or N accumulation in the soil. Estimation of soil N stock changes based on yearly total N concentration measurements in the topsoil layer is currently ongoing. Preliminary results suggest that soil N stocks in the topsoil decreased under all treatments more than expected from the N balance, and that positive N balances are needed to maintain topsoil N stocks. An increase in soil N concentration was observed in none of the treatments. In conclusion, the results indicate an efficiency-sustainability trade-off. Treatments with a higher NUE lose more soil stock N than those with a lower NUE. Treatments with lower NUE indicate higher N losses from the studied crop-topsoil system. Sustainable soil N management in addition to organic fertilizer inputs might at this site require reduced soil tillage. The significance of N contained in deeper soil layers, and deep rooting crops in recovering leached N should as well be investigated

Nitrogen budgets and soil nitrogen stocks of organic and conventional cropping systems: how reconcile efficiency and sustainability of nitrogen use?

Organic and conventional cropping systems differ in the nature and amounts of nitrogen (N) inputs, which may affect efficiency and sustainability of N use. In the DOK (bio-Dynamic, bio-Organic, Konventionell) field experiment, organic and conventional cropping systems have been compared since 1978 at two fertilization levels (with level 2 being typical for the respective system and level 1 receiving half of this dose)

Using a Tri-Isotope (13C, 15N, 33P) Labelling Method to Quantify Rhizodeposition

Belowground (BG) plant resource allocation, including roots and rhizodeposition, is a major source of soil organic matter. Knowledge on the amounts and turnover of BG carbon (C), nitrogen (N), and phosphorus (P) in soil is critical to the understanding of how these elements cycle in soil-plant system. However, the assumptions underlying the quantification and tracking of rhizodeposition using isotope labeling methods have hardly been tested. The main objectives of this chapter were to (i) review the different plant labeling techniques for each of the three elements; (ii) describe a novel method for the simultaneous investigation of C, N, and P rhizodeposition in sand; and (iii) test the methodological assumptions underlying quantification of rhizodeposition. Stable 13C and 15N isotopes were widely used to study rhizodeposition of plants either separately or in combination, while P radioisotopes (32P, 33P) were used to investigate root distribution. The combination of the 13CO2 single-pulse labeling with the simultaneous 15N and 33P cotton-wick stem feeding effectively labeled Canavalia brasiliensis roots and facilitated the estimation of rhizodeposited C, N, and P input from root systems. However, the isotope distribution was uneven within the root system for all three elements. Additionally, we observed a progressive translocation from shoot to roots for 15N and 33P over 15 days after labeling, while the 13C tracer was diluted with newly assimilated non-enriched C compounds over time. Younger root sections also showed higher specific activities (33P/31P) than the older ones. The relatively high 33P radioactivity recovered in sand right away at the first sampling was attributed to an artifact generated by the stem feeding labeling method. Overall, our results suggest that the assumptions underlying the use of isotope methods for studying rhizodeposition are violated, which will affect the extent of quantification of rhizodeposition. The consequences of nonhomogeneous labeling of root segments of different age require further investigation. The use of a time-integrated isotopic composition of the root is recommended to not only account for temporal variation of isotopes but also to improve the method of quantifying plant rhizodeposition