Maize root growth and P uptake dependency on spatial distribution of sewage sludge, sewage sludge ash, and TSP

Shoot P uptake from TSP was largely increased by the localized placement. For the ASH, the localized placement clearly decreased shoot P uptake from the ash. For Sewage Sludge, localized placement decreased P uptake from the soil whereas P uptake from the sludge was almost unaffected. • Overall, total shoot P uptake was significantly affected by the treatment (p<0.005)

Symbiotische N2 Fixierung und N–Bilanz von Soja unter Be-rücksichtigung der N-Rhizodeposition im DOK Versuch

Symbiotic N2 fixation (Nfix) and N-balance was determined from organic and conven-tional grown soybean in the DOK experiment (Switzerland). Nfix was calculated i) based solely on soybean aboveground N (AGN) and ii) additionally taking into account belowground N (BGN), comprising N in physical roots and N rhizodeposition. Nfix was averagely two times higher considering AGN and BGN, ranging from 22 g N m-2 (conventional manure) to 37 g N m-2 (conventional mineral). N balances were positive in all treatments, but with 2 – 7 g N m-2 based on AGN solely comparatively small. These values were exceeded fourfold when considering BGN ranging from 13 g N m-2 (conventional manure) to 21 g N m-2 (organic and conventional mineral)

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

Below ground nitrogen dynamics in the sequence clover-grass maize in the DOK long term experiment

We investigated the effect of organic versus conventional cropping systems on the below ground nitrogen inputs of Trifolium pratense L., its transfer to corresponding grass and the fate in the soil organic matter in the clover-grass ley of the DOK long term experiment, Switzerland. BGN tended to be largest in conventional and organic treatments with standard fertilisation and decreased with lower fertilisation intensity. The largest amount of clover N transferred to grass was observed in the minerally fertilised conventional treatment. Clover N derived from rhizodeposition was rapidly stabilised in all treatments to clay rich fractions and thus clover N will have a relatively low direct N contribution to subsequent nonlegumes

Fresh and residual phosphorus uptake by ryegrass from soils with different fertilization histories

Organic farming largely depends on animal manure as a source of phosphorus (P) and the recycling of animal manure globally is becoming increasingly important. In a pot experiment, using radioactive P labeling techniques, we studied ryegrass uptake of P applied with animal manure and water soluble mineral fertilizer to soils that had been cropped for 22years according to organic or conventional farming practices. The soils differed in P status and microbial activity. Labeling soil-available P also allowed assessing the uptake from residual P that remained in the soils because of their different fertilization histories. On each soil, recovery of fresh manure P in four harvests of ryegrass shoots was lower than recovery of mineral P. It ranged from 24% to 35% for manure P and from 37% to 43% for mineral P. Recovery of fresh manure P was affected by soil-available P contents. It was lower at a higher available P in a conventional soil. Different levels in microbial activity among soils were of lesser importance for the recovery of fresh manure P in plants. The recovery of residual P ranged from 9% to 15%. Residual P contained in organic cropped soils contributed less to P nutrition of ryegrass than the residual P contained in conventional cropped soils, probably due to their lower residual P contents being composed of stable P forms. The indirect isotope dilution technique is useful in assessing manure P uptake by plants, but attention must be given to added P interactions, i.e., the potential impact of organic amendments on P uptake from non-labeled soil and residual

Symbiotische Stickstofffixierung in biologisch und konventionell bewirtschafteten Wiesen

Because of lower nitrogen (N) input it is assumed that organically cultivated legumes fix more N2 than legumes grown under conventional cropping. Using the natural 15N abundance method, we assessed symbiotic N2 fixation by white and red clover. The clover was growing in a grass-clover meadow installed as part of the crop rotation of a long term (30 years) field experiment. Dry matter yields were similar for organic and conventional meadows on plots fertilized at levels typical for the respective system, but organic meadows tended to higher clover yields. The proportion of N derived from atmosphere (Ndfa) in both clover species was on average 84%. It was not significantly affected by the cropping system. Because of more legumes, amounts of fixed N2 (Nfix) were higher in organic than conventional meadows. Under low fertilization intensity, low available potassium and phosphorus contents limited Nfix through lower legume dry matter production while Ndfa remained high

Symbiotic N2 fixation by soybean in organic and conventional cropping systems

In organic cropping systems nitrogen (N) often limits agricultural production. N2 fixing crops present an important option to improve N supply and to maintain soil fertility. We investigated N2 fixation of soybean in conventional and organic cropping systems. The study was carried out on a long term field experiment, characterized by unequal fertilization rates and soil microbial activity for the different systems. We assessed the proportion of N derived from atmosphere (Ndfa) and the total amount of N symbiotically fixed (Nfix) using the 15N natural abundance method. Ndfa for soybean was low, ranging from 24 to 54%. The lowest Ndfa was reported for the exclusively mineral fertilized, and the highest for the bio-organic cropping system. However, there were no differences between the farming systems in total amount of N symbiotically fixed. Irrespective of the cropping system, N withdrawal by harvest was higher than N input by N2 fixation, meaning that soil N stock was not preserved

Tracing the fate of 15N-labelled animal manure in the environment

Background • Nitrate leaching threatens both the environment and drinking water quality • Switzerland ca. 380,000 ha with > 25 mg nitrate/L in groundwater (quality criteria for drinking water) [1]; the Gäu region (Canton Solothurn) is especially vulnerable • Organic fertilizers (slurry, farmyard manure, etc.) might entail considerably increased leaching risks due to variable nitrogen (N) content and availability • Aim: increase N use efficiency, simultaneously reduce leachin

Einfluss unterschiedlicher Bewirtschaftungsverfahren auf P-Formen und P-Dynamik im Boden

The impact of cropping systems on soil phosphorus (P) forms and P dynamics was studied. The systems were a biodynamic (DYN), a bioorganic (BIO), a conventional (CON), a stockless system (MIN) and an unfertilized control (NON). These cropping systems are part of the DOK field trial in Therwil near Basel. The systems differed in fertilization and plant protection. The P budgets over 30 years were negative except for CON and increased in the order: NON < DYN < ORG < MIN < CON. A sequential P extraction scheme was used to characterize the P forms in soil samples from 2007 and 1977 (before the start of the trial). Labile inorganic P (Pi) forms differed significantly between cropping systems. Organic P forms (Po) and stable Pi forms were not affected by the cropping systems apart from Po in concentrated HCl extract. The comparison between P forms in the soils of 2007 and 1977 revealed depletion in labile Pi forms in all systems. The changes were related to the P budget. Po changes were small and thus most of Po appears to be strongly stabilized in the soil

Wurzelbürtige Stickstoff- und Kohlenstoffeinträge in den Boden: Erkenntnisse aus sieben Jahren DOK Wurzelforschung

We investigated nitrogen and carbon below ground inputs of soybean, clover-grass and maize and management effects of biological and conventional systems in the DOK long term experiment. We found for soybean increasing below ground C and N inputs with decreasing fertilization intensity whereas those effects were small for clover-grass. Below ground nitrogen inputs of red clover could be estimated by above ground N multiplied with a factor of 0.5