Because of the complexity of farmingsystems, the combined effects of farm management practices on nitrogen availability,nitrogen uptake by the crop and crop performance are not well understood. Toevaluate the effects of thetemporal and spatial variability of management practices, we used data fromseventeen farms and projections to latent structures analysis (PLS) to examinethe contribution of 11 farm characteristics and 18 field managementpractices on barley performance during the period 2009–2012. Farm typeswere mixed (croplivestock) and arable and were categorized as old organic,young organic or conventional farms. The barley performance indicators includednitrogen concentrations in biomass (in grain and whole biomass) and dry matterat two growing stages. Fourteen out of 29 farm characteristics and field managementpractices analysed best explained the variation of the barley performanceindicators, at the level of 56%, while model cross-validation revealed agoodness of prediction of 31%. Greater crop diversification on farm,e.g., a high proportion of rotational leys and pasture, which was mostlyobserved among old organic farms, positively affected grain nitrogen concentration.The highest average grain nitrogen concentration was found in old organic farms(2.3% vs. 1.7 and 1.4% for conventional and young organic farms, respectively).The total nitrogen translocated in grain was highest among conventional farms(80 kg ha−1 vs. 33 and 39 kgha−1 for young and oldorganic farms, respectively). The use of mineral fertilizers and pesticidesincreased biomass leading to significant differences in average grain yieldwhich became more than double for conventional farms (477 ± 24 g m−2) compared toorganic farms (223 ± 37 and 196 ± 32 g m−2 for young and old organic farms,respectively). In addition to the importance of weed control, management ofcrop residues and the organic fertilizer application methods in the current andthree previous years, were identified as important factors affecting the barleyperformance indicators that need closer investigation. With the PLS approach,we were able to highlight the management practices most relevant to barleyperformance in different farm types. The use of mineral fertilizers and pesticideson conventional farms was related to high cereal crop biomass. Organicmanagement practices in old organic farms increased barley N concentration butthere is a need for improved management practices to increase biomassproduction and grain yield. Weed control, inclusion of more leys in rotationand organic fertilizer application techniques are some of the examples ofmanagement practices to be improved for higher N concentrations and biomassyields on organic farms. |
