Preceding crops influence agronomic efficiency in sugar beet cultivation

The choice of the crop succession influences the agronomic efficiency (yield per unit agronomic input) and is relevant for the sustainable intensification of crop cultivation. However, such effects are often ignored in assessments of agronomic efficiency. The aim of the study was to propose a concept for the assessment of and to publish data on (i) the effect of the preceding crop on the amount of agronomic inputs used and the yield in sugar beet cultivation and (ii) the agronomic efficiency of the 2-year sum of preceding crop - sugar beet successions. As preceding crop (including catch crop) - sugar beet successions, we investigated (i) mustard - silage maize - sugar beet, (ii) phacelia - grain pea - mustard - sugar beet, and (iii) winter wheat - mustard - sugar beet in a field trial (Harste, Germany; 2011-2014). We found that fertilizer requirement of sugar beet was highest (108 kg nitrogen ha(-1); 125 kg phosphate ha-1) when mustard - silage maize was the preceding crop and lowest (30 kg nitrogen ha(-1); 96 kg phosphate ha(-1)) when phacelia - grain pea - mustard was the preceding crop. The efficiency of the agronomic inputs used for the cultivation of the 2-year sum of preceding crop - sugar beet successions was generally highest for the succession with silage maize with the exception of nitrogen-efficiency which was highest for the succession with grain pea. The main effect of the preceding crop on fertilizer requirement was driven by the amount of harvest residues. Results of 2-year agronomic efficiency were affected by the high energy yield of the succession with silage maize (670 GJ ha(-1)) and the low N-fertilization in the succession with grain pea (130 kg N ha(-1)). We show for the first time a methodological approach to assess preceding crop's effects on agronomic efficiency and to illustrate results for decision making towards a sustainable intensification of crop cultivation.