Nitrogen management in organic farming: comparison of crop rotation residual effects on yields, N leaching and soil conditions

Abstract

After 3 years of different crop rotations in an organic farming experiment on a sandy soil in northwest Germany, spring triticale was cultivated on all plots in the fourth year to investigate residual effects on yield, nitrogen (N) leaching and nutrient status in the soil. Previous crop rotations differed in the way N was supplied, either by farmyard manure (FYM, 100 and 200 kg N ha -1 year -1 ) or by arable legumes like grass-red clover and field beans, or as a control with no N. Other crops in the rotations were maize, winter triticale and spring barley. Additional plots had a 3-year grass-clover ley, that was ploughed-in for spring triticale in the fourth year. Yields of spring triticale were moderate and largest for ploughed-in grassland leys and grass-red clover and plots that had previously received farmyard manure. The former crop rotation, including grassland break-up, had a significant effect on most yield and environmental parameters like residual soil mineral nitrogen (SMN) and N leaching and on the level of available K in the soil. The single crop harvested in the year before spring triticale had a significant effect on yield parameters of spring triticale, less so on SMN and N leaching in the fourth year and no effect on available nutrients (P, K, Mg) and pH in the soil. We conclude that the effects of arable legumes were rather short lived while ploughing of 3-year grassland leys had a profound influence on mineralization processes and subsequently on yield and N losses.

Reviews and syntheses: Review of causes and sources of N<sub>2</sub>O emissions and NO<sub>3</sub> leaching from organic arable crop rotations

“…Previous reviews have compared the net N 2 O emissions and NO 3 leaching from these systems. Lower areascaled, but roughly similar yield-scaled emissions (slightly higher, similar or slightly lower) are commonly observed for N 2 O emissions (Tuomisto et al, 2012;Skinner et al, 2014Skinner et al, , 2019 and NO 3 leaching (Kirchmann and Bergström, 2001;Stopes et al, 2002;Aronsson et al, 2007;Tuomisto et al, 2012;Benoit et al, 2014) from organic versus non-organic arable crop production.…”

“…On average over 3 years on loamy sand in Denmark, De Notaris et al (2018) reported NO 3 leaching that was about twice as high following a barley-pea intercrop compared with spring wheat or spring barley. In a sandy soil in northwestern Germany, Kayser et al (2010) observed that 83 kg N ha −1 leached in triticale following field bean. In a worst-case scenario, Askegaard et al (2011) observed annual NO 3 leaching of 270 kg N ha −1 during and after a lupin crop on a course sandy soil in a situation where the lupin crop did not ripen, leaving a large amount of N in crop residues (same experiment as De Notaris et al, 2018).…”

“…1 and an overview of performance of selected drivers of SMN in organic and non-organic crop rotations are given in Table 1. Despite substantial inputs of N from biological nitrogen fixation (BNF;Kayser et al, 2010;Pandey et al, 2017) and from organic amendments, the N supply is often below op-timum for plant growth in arable organic farming (Berry et al, 2002;Tuomisto et al, 2012). BNF may be a more important N source than N from organic manures and fertilisers in organic arable cropping systems (Pandey et al, 2018).…”

“…Even in the year following the termination of a ley, the con- tent of SMN can still be high (Hansen et al, 2007;Jończyk and Martyniuk, 2017). Kayser et al (2010) pointed out that N provided by spring ploughing of both a 1-year grass-clover ley and a 3-year grassland ley resulted in high concentrations of SMN (0-90 cm, 61 kg N ha −1 and 95 kg N ha −1 , respectively) in the following autumn after harvest of spring triticale. Much of this SMN may not have been available for the crops during spring and is likely to have been mineralised after the end of the growing season.…”

Nitrogen mineralization simulation dynamic in tobacco soil

“…This study also demonstrate positive effects that a shortterm (5 year) pasture can have on soil organic matter quantity and quality and its attendant benefits on soil N mineralization and soil structure. Farmyard manure application and returning leguminous crop residue to the field can increase the soil organic nitrogen mineralization and leaching risk (Kayser et al 2010). Fertilization of mid-rotation in Pinus radiata plantations makes unexpected sustained growth responses for more than 6 years and volume gains of 25m 3 ha -1 and 50m 3 ha -1 in sandy and granitic soil.…”