Berit Tein

Soil Nutrient Evolution during the First Rotation in Organic and Conventional Farming Systems

Since 2008, a 5-year crop rotation experiment (winter wheat, pea, potato, barley undersown with red clover, and red clover) has been run in Tartu, Estonia, to evaluate the changes in soil chemical parameters under four fertilizer managements: (1) unfertilized conventional plots (conventional I), (2) conventional plots with addition of mineral fertilizers (conventional II), (3) organic plots with cover crops during the winter period (organic I), and (4) organic plots with the same cover crops plus a yearly amendment of 40 t ha–1 of cattle manure (organic II). After the first rotation, results showed significant differences (P < 0.05) in soil acidity dependent on the system with mean values ranging between 5.67 (conventional II) and 6.10 (organic II). In the organic II system, manure had a significant effect on the system, increasing the organic carbon (C) content by 0.34%, but in both organic systems, both cover crops and cattle manure were insufficient for maintaining a constant level of plant-available phosphorus (P) or potassium (K) in the soil. In the conventional II system, mineral fertilizers provided a sufficient amount of nitrogen (N) to the system and increased the concentration of P to 8.7 mg per kg. The yearly mineral or organic amendments did not counteract the significant decrease in soil-available K after the first rotation. Lastly, calcium (Ca) and magnesium (Mg) availability, strongly influenced by the soil pH local conditions, decreased with time for all systems even though organic ones presented greater concentrations of both compounds. In conclusion, the four fertilization systems managed independently would not guarantee a constant soil nutrient concentration after the first rotation.

Early blight destroys potato foliage in the northern Baltic region

In recent years, potato early blight [Alternaria solani (Ellis & G. Martin) L.R. Jones, A lternaria alternata (Fr.) Keissl.] has occurred with increasing frequency in European potato fields, including those in northern regions. In our study, early blight was evaluated during the two years 2010–2011 on potato plants in a conventional farming experiment. Both growing seasons were very favourable for early blight development and evaluation. Our study indicates that, despite chemical treatments, potato early blight is a great problem for potato growers in conventional farming systems in the North-East region in years when temperatures are higher than average. In 2011, early blight damage was particularly high on the untreated (N0P0K0) treatment plots where severity increased abruptly from an initial 2% to 91%, and killed the potato haulms within five weeks. In 2010, the most severely infected plants were also recorded on the untreated (N0P0K0) plots, where 70% of foliage was destroyed by the end of the growing season. Results showed that a more efficient chemical strategy is needed against this disease on susceptible cultivars. Breeding and growing more resistant cultivars of potato is considered the most efficient, cost effective and environmentally friendly control method for sustainable cultivation in conventional growing systems. As an increase in the frequency of warmer summers is predicted, greater problems from this pathogen are to be expected in Northern Europe.

Winter cover crop effects on soil structural stability and microbiological activity in organic farming

Abstract In a field experiment based on a five-year crop rotation (pea, potato, barley undersown with red clover, red clover and winter wheat), several soil parameters, porosity, number and biomass of earthworms, total nitrogen, organic carbon, percentage of water stable aggregates and enzymatic activity, were studied during 2013 and 2014, the first and second year, respectively, since the first rotation concluded. This rotation was managed under three organic farming systems: Organic 0 (control), Organic I (with winter cover crops lately incorporated into the soil as green manure) and Organic II (with the same cover crops plus a yearly amendment of 40 t ha−1 of cattle manure). Crop rotation had a yearly positive effect on the soil bulk density, and enhanced the percentage of air filled pores; nonetheless, despite the leguminous crops in the rotation, all the systems presented a yearly decrease in total nitrogen in 2014. Cover crops along with manure only had a significant effect on enzymatic activity; however no significant effect was found in soil organic carbon content, soil particle aggregability or number and biomass of earthworms. This was connected with the intensive tillage carried out in the systems, the weather conditions and the characteristics of the organic amendments. However according to other studies these results could be transient and further long-term investigations will be needed.

Barley undersown with red clover in organic and conventional systems: nitrogen aftereffect on legume growth Miežiai su raudonųjų dobilų įsėliu ekologinės ir tradicinės žemdirbystės sistemose: azoto įtaka pupinių augalų augimui

Nitrogen (N) deficiency is a major problem in organic and low-input farming systems. Growing spring cereals with undersown legumes has a positive effect on soil fertility, enriching it with nitrogen, through symbiosis of legumes with nodule bacteria. Two hypotheses were tested: 1) undersowing of red clover increases the protein content of barley grains and 2) mineral N has negative aftereffect on growth of legume plants. The aim of this study was to investigate the effect of organic (cattle manure, off-season cover crop) and mineral N in organic and conventional farming systems on (i) barley (Hordeum vulgare L.) grain yield and quality, (ii) biomass yield formation of undersown red clover (Trifolium pratense L.) and (iii) the aftereffect of mineral and organic N fertilisers on the red clover crop biomass yield in the following year. The experiment was established in 2008 at the Estonian University of Life Sciences (58°22ʹ N, 26°40ʹ E) on the soil described as Stagnic Albic Luvisol (LV ab-st) (WRB, 2014) with sandy loam surface texture, 1.38% C, 0.13% N, 133 mg kg-1 P, 210 mg kg-1 K and pHKCl 6.0. The crops were treated using different farming systems: three organic (Org0, OrgI and OrgII) and four conventional (N0, N40, N80 and N120); nitrogen sources during crop cycle period: N0 and Org0 = symbiotically fixed atmospheric N2, N40 = N2 + mineral N 40 kg ha-1 N, N80 = N2 + mineral N 80 kg ha-1 N, N120 = N2 + mineral N 120 kg ha-1 N, OrgI = N2 + N taken up by cover crops (NCC) and OrgII = N2 + NCC + N applied with manure (Nm). Our study revealed that grain yield of barley was strongly affected by undersown red clover; because of competition for nutrients in cereallegume mixture the grain yield of barley in organic system was 11‒61% lower than that in conventional system. The seed rate of undersown red clover (2.84 million viable seed per ha) was too high. The content of proteiin depended on the availability of mineralised nitrogen. The mean protein content of barley grains over the trial years and treatments was 99 ± 1.6 g kg-1 in the conventional system, which was 17% higher than that in the organic system. Undersowing of red clover had no significantly positive effect on the grain yield and protein content of barley. Mineral N fertiliser had no negative aftereffect on growth of the red clover crop the following year. Mean above ground biomass yield over the trial years for the red clover crop 2nd cut was 17% higher in the conventional system than in the organic system.