Transfer of Grain Legume Nitrogen within a Crop Rotation Containing Winter Wheat and Winter Barley

In a crop rotation trial, conducted from 1985 to 1988 at TU-Munich's research station in Roggenstein, the transfer of grain legume nitrogen was evaluated in crop rotations containing fababeans and dry peas as well as oats (reference crop) and winter wheat and winter barley as following crops. The results obtained can be summarized as follows: Dinitrogen fixation by fababeans ranged from 165 to 240 kg N ha¹, whereas N₂-fixation by peas amounted from 215 to 246 kg N ha^?1. In all seasons the calculated N-balance where only grain was removed was positive, with a net gain being on average 106 (peas) and 84 (fababeans) kg N ha^?1. After the harvest of peas 202 kg N ha^?1 remained on the field on average over seasons (158 kg N ha^?1 in the above ground biomass and 44 kg N ha^?1 as NO₃-N in 0–90 cm depth). As compared to peas, fababeans left 41 kg N ha^?1 less due to smaller amounts of nitrogen in the straw. After oats very small amounts of residual nitrogen (33 kg N ha^?1) were detected. After the harvest of grain legumes always a very high nitrogen mineralization was observed during autumn especially after peas due to a close C/N-relationship and higher amounts of nitrogen in the straw as compared to fababeans. In comparison with fababeans, N-mineralization after the cultivation of oats remained lower by more than 50%. During winter, seepage water regularly led to a considerable decrease of soil NO₃-N content. The N-leaching losses were especially high after cultivation of peas (80 kg N ha ^?1) and considerably lower after fababeans (50 kg N ha^?1) and oats (20 kg N ha^?1). As compared to oats, a higher NO₃-N content in soil was determined at the beginning of the growing period after preceding grain legumes. Therefore, winter wheat yielded highest after preceding peas (68 dt ha^?1) and fababeans (60 dt ha^?1) and lowest after preceding oats (42 dt ha^?1). The cultivation of grain legumes had no measurable effect on yield formation of the third crop winter barley in either of the growing seasons.     

Effect of varied N rates and N timings on yield, N uptake and fertilizer N use efficiency of a six-row and a two-row winter barley

The effects of N rates and N timings on yield formation, N uptake at five growth stages and fertilizer N use efficiency of six-row and two-row winter barley were evaluated in field trials conducted from 1990/91 to 1992/93 at the TU Munich's research station Roggenstein.

On average over 3 years the six-row cultivar yielded most at a total rate of 110 kg ha⁻¹ N including an early application of 40 kg ha⁻¹ N up to EC 30 (Zadoks scale). The two-row cultivar achieved maximum yield at a total rate of 140 kg ha⁻¹ N including early applications of 70 kg ha⁻¹ N up to EC 30. The highest yielding N-treatments of six-row barley regularly took up less nitrogen at EC 32 (95 kg ha⁻¹ N on average) than the non-optimally fertilized treatments, whereas full exploitation of the yield potential of two-row barley was associated with higher rates of N-uptake at EC 32 (113 kg ha⁻¹ N on average).

Lodging did not occur in the trials conducted in 1991 and 1992 and no difference was detected between the two cultivars in fertilizer N use efficiency. With six-row barley the N treatment giving maximum yield also led to an optimum fertilizer N use efficiency. Full exploitation of the two-row barley yield potential was associated with suboptimal fertilizer N use efficiencies.     

Vertikaler Wasser- und Nitrattransport in tiefere Bodenschichten süddeutscher Ackerstandorte

Vertical water and nitrate movement into deeper soil layers on fields located in the south of Germany In Southern Bavaria, selected fields from deep loess and sandy sediments were sampled to a depth of maximum 10 m every 4 months, in order to determine the basic processes of water and nitrate movement in the course of the year. The downward movement of water and nitrate followed the principle of piston flow only in the intermediate vadose zone of loess soils with a leaching distance amounting 0.8 m per year. On the other hand, an accelerated as well as a delayed transport was observed in the zone of evapotranspiration of loess soils and in the whole profile of sandy soils, not being in accordance with the simple simulation model FLOTRA based on the classic theories of transport (Darcy flow, convection-dispersion-equation). Preferential flow led to the leaching of nitrate from the top soil to the lower boundary of the evapotranspiration zone of loess soils in 2 m depth, in winter and spring. In sandy soils nitrate was leached to the groundwater table in 4–6 m depth after extensive rainfall.     

Effect of Long-term Application of Farmyard Manure on Growth and Quality of Sugar Beet

Field trials were conducted for two years on two farms which differed in long-term application of pig slurry in order to study the effects of long-term organic manuring, timing of slurry application (no slurry, slurry autumn, slurry spring) and additional doses of mineral N-fertilizer (0, 80, 160, 240 kg N/ha) on growth and quality of sugar beet. The results can be summarized as follows: 1. The effect of slurry application on growth of sugar beets varied markedly with the long-term differences in farm management. On the “arable farm” yield of beet roots increased substantially after slurry application and could not be replaced by higher doses of mineral N fertilizer. It is concluded therefore that “special effects” of farmyard manure are involved. On the “livestock farm”, however, highest beet yields were obtained on plots without slurry. Additionally slurry application caused a significant decrease in beet yields. 2. Sugar beets without slurry treatment always developed higher sugar contents and lower concentrations of alpha-amino-N, sodium and potassium as compared to beets from plots with slurry application. 3. Despite the decline in sugar content, sugar yield greatly increased by slurry application on the “arable farm”. The average increase in sugar yield was 10 dt/ha (=8%) with slurry application in autumn and amounted to 16 dt/ha (=14%) with spring application. On the livestock farm however, additional applications of slurry caused a decline in sugar yields in both years because of lower sugar contents and decrease in beet yields. 4. The utilization rate of slurry-N, depending mainly on time of application, annual rainfall and soil N mineralization, varied from 6–41%. On the “livestock farm” the utilization of slurry-N was only half of the rate obtained on the “arable farm”. 5. The application of small doses of slurry may cause a significant yield increase on farms without or only less livestock, while on farms with intensive livestock production continous slurry application needs to be considered as an expensive form of waste disposal. Therefore farms with high livestock density are advised to sell slurry to neighbouring farms without or only low animal production at a fair price for their mutual advantage.     

Ursachen kleinräumiger Ertragsschwankungen im bayerischen Tertiärhügelland und Folgerungen für eine teilschlagbezogene Düngung

Site effects of small-scale yield variation in the Tertiary hills north of Munich (Germany) and conclusions for site specific farming The effect of numerous soil factors on small-scale yield variation of winter wheat and spring barley were examined: soil structure and soil texture, soil nitrate content and soil water at different times, P_CAL-, K_CAL-, N_t- and C_t-content, pH, soil microbiology characteristics, relief, root growth and important plant diseases. The varying annual influence of soil parameters on crop yield was interrelated with climatic factors. In soils with low sand content soil productivity was largely influenced by soil structure. This effect was less pronounced on soils with medium sand content. On sandy soils, however, yield was reduced by available water capacity. Yield potential was also lowered by frequent cereal growing associated with take-all root desease of winter wheat. High yield variation from year to year confirmed that a site-specific crop management should consider annual variability of yield in addition to soil conditions and yield measurement. Site-specific N fertilization should be adapted to the actual progress of plant growth.     

Nitratabbau in tieferen Bodenschichten süddeutscher Ackerstandorte auf Löß

Denitrification in deeper soil layers of arable land in southern Germany This study deals with the attempt to determine nitrate losses by denitrification in deeper soil layers by means of balancing the nitrate and chloride contents in the depth profiles of repeatedly sampled locations on deep sediments derived from loess in southern Germany. The extent of the nitrate losses was dependent on nitrate concentration. In the intermediate vadose zone, high rales of denitrification up to 0.5 kg NO₃?N/(ha·d·0.33 m) were detected, if nitrate concentration was high. In no case complete denitrification occurred. The preconditions for denitrification in deeper soil was determined by the soil profile. Nitrate reduction was favoured by small proportions of aerated pores. Increased organic C contents derived from the layer of an interstadiale soil formation (Würm) and reduced sulfur in the Würm loess were found as reduced substrates for denitrification.     

Validierung eines 2-Regionen-Modells zur Simulation des Stofftransportes im Boden anhand von Laborsäulen- und Feldversuchen

Validation of a 2-domain-model for the simulation of solute transfer in soils by laboratory and field experiments The simulation of water and solute transfer in the unsaturated zone on the basis of the classical convective dispersive model gives dissatisfactory results in many cases. Especially in the zone of evapotranspiration the observed penetration depths of surface-applied chemicals often exceed calculated values. This has been attributed to preferential flow in domains with accelerated flow. The aim of the investigations presented here was to extend the conventional theory of solute transfer in order to enable improved model predictions without introducing too much complexity to the model which might reduce its applicability. The mobile-immobile-concept of Coats and Smith (1964) was chosen to extend the model FLOTRA (Wagner et al., 1992), which is based on the convective dispersive approach. The model parameters additionally needed by the model are the immobile water content θ_im and the solute transfer coefficient α. The applicability of the model was tested on the basis of several laboratory and field experiments. It is shown, that with the mobile-immobile-approach modeling results of water and solute transfer in the top soil layers, which are most important in view of soil and groundwater protection, were improved compared to the calculations with the classical convective dispersive model.     

Standorterhebungen zur Stickstoffdynamik nach Anbau von Körnerleguminosen

Field studies on nitrogen dynamics after cultivation of grain legumes Field trials were conducted in order to study the nitrogen dynamics in soil after cultivation of grain legumes and to investigate the possibility of reduction of nitrate leaching due to catch crops or suitable following crops. Accordingly, in 1989/90 soil samples were taken on 12 farms at depths of 0–80 cm in 4 week intervals and analysed for NO₃-N. Furthermore, Brassica napus and Sinapis alba were sown after grain legumes on two farms, and at the experimental station Roggenstein field trials were carried out with different catch crops (Sinapis alba, Raphanus sativus, Lolium multiflorum and Pisum sativum) after grain peas. Considerable amounts of nitrogen (100–150 kg N/ha) in the form of crop residues (straw and grains) were left on the fields cultivated with grain legumes. After harvesting, nitrate content in the soil layer 0–80 cm was on grain legume fields almost twice as high as on fields cultivated with winter wheat. During autumn, the soil nitrate contents increased remarkably. In the soil layer 0–80 cm the maximum values rose to 140 kg N/ha after peas, to 120 kg N/ha after faba beans and only to 65 kg N/ha after winter wheat. The more intensive N-mineralization after peas compared to faba beans is due to a lower C/N-ratio of crop residues and an earlier harvest time of 2-3 weeks of peas. In winter extremely high N-leaching was measured on fallow land after cultivation of grain legumes. Cultivation of catch crops makes it possible to retain up to 110 kg N/ha in plant material. Raphanus sativus and Sinapis alba are most suitable for this purpose due to their high N-uptake even when they are sown late. Ploughing up catch crops in autumn results in a fast mineralization of their immobilized nitrogen. This implies the risk of N-leaching into deeper soil layers during winter, depending on the amount of rainfall and water capacity of the soil. Particularly on soils with low water capacity, early N-mineralization needs to be prevented by cultivating catch crops which freeze off or survive in winter. Cultivation of Brassica napus (winter form) after grain legumes leads to an extensive uptake of soil nitrate before the beginning of the seepage period, and therefore almost excludes enhanced N-leaching.     

Auswirkungen differenzierter Bodenbearbeitung auf das Bodengefüge und die Stickstoffdynamik von Lößböden bei viehloser und viehstarker Bewirtschaftung

Effect of different tillage practices on soil structure and nitrogen dynamic in loess soils with and without longterm application of farmyard manure
Field trials were conducted in 1979 and 1980 on two farms with and without longterm application of farmyard manure respectively, to study the effect of different tillage practices (ploughing at low soil moisture in summer and autumn and ploughing at highsoil moisture in autumn) on soil structure and nitrogen dynamic. Soil structure measurements showed great differences between ploughing at low and high soil moisture contents. Ploughing soil at high moisture contents caused a rise in penetrometer resistance as in bulk density and a decrease of macropors as well as in oxygen concentration in top soil and in tillage pan. But little differences were observed between ploughing in summer and autumn at low soil moisture contents.
Ploughing soil at high moisture contents caused a higher soil compaction on the farm without longterm application of farmyard manure compared to the farm with longterm application of farmyard manure.
The differences in soil nitrate content were strongly correlated with soil compaction. Very large differences in soil nitrate content between ploughing at low and high soil moisture contents were always observed in May, when the soil temperature was higher than 15°C These differences in soil nitrate content are due to reduced nitrogen mineralization and an increase of denitrification activity after ploughing at high soil moisture contents.     

Effects of Long-term Application of Slurry on Soil Nitrogen Mineralization

Field trials were conducted for two years on two farms which differed in long-term application of slurry in order to study the long-term effect of slurry and the effect of application time (no slurry, slurry autumn, slurry spring) on the dynamics of nitrogen in the soil.
The results can be summarized as follows:
On the farm with long-term application of slurry, ("livestock farm"), nitrate-content in the soil was markedly higher than on the farm without slurry application ("arable farm"). This is due to a more intensive N-mineralization during autumn and spring. On the livestock farm a remarkably high mineralization of nitrogen was observed at soil temperatures near 0°C, while on the "arable farm" N-mineralization started only at temperatures above +4°C.
The high N-mineralization during autumn on the "livestock farm" implies the risk of N leaching into deeper soil layers during winter.
Slurry application caused a large increase of mineralized nitrogen in soil. No site-differences in decomposition of actual slurry applications have been observed.
High N infiltration-rates may occur when slurry is applied in autumn, depending on the amount of autumn and winter rainfall. Thes risk of nitrogen leaching also persists, when slurry is applied in spring and crops with late N-uptake are cultivated (e.g. sugar beet).
The intensive leaching of nitrogen after application of slurry is caused by the fast nitrification of slurry-NH₄, which may happen even at low temperatures.