Liina Talgre

Changes in agricultural land use and in plant nutrient balances of arable soils in Estonia

Abstract The aim of the present study was to assess the impact of changes in agricultural land use and in the plant nutrient balances on the degradation of soils in Estonia. The plant nutrient balances of arable soils in Estonia were calculated at the national level. After the re-establishment of the independence of Estonia, in the transition to market economy, agricultural production has undergone a drastic decline. Agricultural land use has declined most of all in the regions with low soil fertility. Decreased and low-input agricultural production has reduced pressure on the surrounding environment but owing to the inadequate use of fertilizers, the balance of the main plant nutrients is at present negative. In the 1990s, crop production has occurred largely at the expense of soil resources. Current agri-environmental policy should be supplemented with measures for preventing degradation of soils due to the depletion of plant nutrient reserves of arable soils.

The effects of pure and undersowing green manures on yields of succeeding spring cereals

Abstract A field experiment was conducted in 2004–2006 to investigate the effect of green manure treatments on the yield of oats and spring barley. In the experiment, different green manure crops with undersowing and pure sowing were compared for amounts of N, C, and organic matter driven into soil and their effect on cereal yield. The spring barley field had a total of 41.7–62.4 kg N ha−1 and 1.75–2.81 Mg C ha−1 added to the soil with straw, weed, and roots, depending on the level of fertilisation; with red clover, and both common and hybrid lucerne undersowing, with barley straw and roots, the values were 3.45–3.96 Mg C ha−1 and 139.9–184.9 kg N ha−1. Pure sowings of these three leguminous green manure crops had total applications of 3.37–4.14 Mg C ha−1 and 219.7–236.8 kg N ha−1. The mixed and pure sowing of birds-foot trefoil provided considerably less nitrogen and carbon to the soil with the biomass than with the other leguminous crops. Application of biomass with a high C/N ratio reduced the yield of the succeeding spring cereals. Of the green manures, the most effective were red clover and both common and hybrid lucerne, either as undersowing or as pure sowing. Undersowings with barley significantly increased the N supply for the succeeding crop without yield loss of the main crop compared with the unfertilised variant. Compared with ploughing-in of green manure in autumn, spring ploughing gave a 0.2–0.57 Mg ha−1 larger grain yield.

The influence of thermal shock and pre-sprouting of seed potatoes on formation of some yield structure elements

Abstract For earlier potato yield formation we used pre-sprouting and thermal treatment which both add to the physiological age of potato. At the same time, pre-sprouting is a very time- and energy-consuming procedure. We investigated if thermal treatment could replace pre-sprouting and how it affects the growth and development of potato haulms and tubers. For that purpose an experiment was conducted in 2000–2002 to examine the opportunities for growing potatoes by using different methods of pre-planting treatment of seed tubers. Early, middle and late maturing potato varieties (two Estonian varieties and one Latvian) were used, each being subdivided into three variant categories: untreated, thermal shock and pre-sprouting. The experiment indicated that one or the other of thermal shock or pre-sprouting shortened the time to emergence by up to 10 days. With pre-sprouting, the formation of tubers started as soon as 45 days after planting and with thermal shock 50 days after planting, i.e., 5–10 days earlier than in the untreated variant. Thermal shock of seed tubers had the greatest effect on the number of tubers per plant, while pre-sprouting increased the average weight of tubers. Both pre-sprouting and thermal shock had a strong effect on the weight of the haulms in varieties with a longer growth period.

Vetch-wheat crops are superior to vetch-oat crops in terms of protein yield

Abstract The formation of yield in two different combinations: vetch with wheat or oats, and the effect of vetch on yield potential of cereals has been investigated in Estonian field experiments over three years. We found that the inclusion of vetch seed in cereal seed and increase of its seed density led to considerable decrease in the yield of the cereal component (R=0.980–0.998). The adverse effect of vetch on cereal yield led to a reduction in wheat yield by up to 1861 kg ha−1 on average for the three years, and in oats yield by up to 1413 kg ha−1. One reason for the decreases in cereal yields was the formation of smaller grains in cereals under increased vetch seed densities. As a three-year average, the wheat 1000-seed weight decreased by up to 6.3 g while the corresponding figure for oats under identical conditions was 2.5 g. The inclusion of vetch in a crop and the increase of its seed density led to a substantial increase in the protein content of cereal grains. In oats, the change in grain protein content was smaller. At the same time, the maximum protein yield per area unit in cereals was obtained from their monocultures. In a mix with vetch, the amounts of nitrogen consumed by cereals decreased and protein yield of cereals per area unit reduced at higher vetch seed densities. Vetch-cereal mixes had an advantage over cereal monocultures as far as protein yield was concerned. In vetch-wheat and vetch-oats mixes the maximum protein yield was 500 kg ha−1 and 438 kg ha−1, respectively, on average for the three years. Of the two combinations, vetch-oats mixed crop gave the highest yield of grain, whereas the higher mixed crop yield resulted from the oats component. Oats is somewhat more competitive with vetch than wheat. Vetch-wheat mixed crop gave the highest protein yield because the protein content of wheat grains was higher than oat grains. Legume-cereal mixes are particularly suited for the conditions of organic farming as they ensure a relatively good harvest and a high protein yield.

Relating Sentinel-1 interferometric coherence to mowing events on grasslands

In this study, the interferometric coherence calculated from 12-day Sentinel-1 image pairs was analysed in relation to mowing events on agricultural grasslands. Results showed that after a mowing event, median VH (vertical transmit, horizontal receive) and VV (vertical transmit, vertical receive) polarisation coherence values were statistically significantly higher than those from before the event. The shorter the time interval after the mowing event and the first interferometric acquisition, the higher the coherence. The coherence tended to stay higher, even 24 to 36 days after a mowing event. Precipitation caused the coherence to decrease, impeding the detection of a mowing event. Given the three analysed acquisition geometries, it was concluded that afternoon acquisitions and steeper incidence angles were more useful in the context of this study. In the case of morning acquisitions, dew might have caused a decrease of coherence for mowed and unmowed grasslands. Additionally, an increase of coherence after a mowing event was not evident during the rapid growth phase, due to the 12-day separation between the interferometric acquisitions. In future studies, six-day pairs utilising Sentinel-1A and 1B acquisitions should be considered.

Consequences of pre-planting treatments of potato seed tubers on leaf area index formation

Abstract In field trials conducted in 2000–2002, we examined the influence of pre-planting treatments of seed tubers on the formation of leaf area index. The potato varieties used were Agrie Dzeltenie (early), Piret (middle-maturing) and Ants (late). The following treatments were used: untreated control, thermal shock and pre-sprouting. Pre-sprouting treatments of all varieties and thermal shock treatment of the variety Agrie Dzeltenie had a significant effect on the leaf area index. The value and timing of maximum leaf area index were: variety specific, 4.0 units of the early variety Agrie Dzeltenie, 3.7 units of the middle-maturing variety Piret and 3.9 units of the late variety Ants. The weight of the haulms of the plants developed from physiologically older seed tubers formed faster and remained smaller. Pre-planting treatment of seed tubers provided quicker field emergence. The slower the potato plants developed the haulms, the greater the maximum weight achieved. Pre-planting treatments influence the leaf area index. The importance of this influence lies in potato varieties with different maturity times since increases in quality and yield depend on the size of the photosynthetic area.

Phosphorus and potassium release during decomposition of roots and shoots of green manure crops

Decomposition rates of above- and underground biomass and the dynamics of the remaining phosphorus (P) and potassium (K) were studied in trials at the Estonian University of Life Sciences (58°23′N, 26°44′E) in Nordic conditions. The research focused on the decomposition of roots and leaves/shoots of green manure plants. In shoot residues of birds-foot trefoil and white melilot, after 6 months 19% and 20%, respectively, of P remained. Red clover shoots decomposed the slowest, remaining 44% of P in the residue. In a year, legumes remained 20–22% of initial organic P and 11% in 2 years. Rapid release of K from legume shoot residue occurred in 6 months. The roots released K in a period lasting from 6 to 12 months. The roots retained 15–32% K over a year. White clover roots were the slowest in K release. Residue decomposition and P, K release were all influenced by weather conditions.

Do green manures as winter cover crops impact the weediness and crop yield in an organic crop rotation

Abstract The effects of different winter cover crops and their combination with composted cattle manure on weeds and crop yields were investigated within a five-field crop rotation (barley undersown with red clover, red clover, winter wheat, pea, potato) in three organic cropping systems. The control system (Org 0) followed the rotation. In organic systems Org I and Org II the winter cover crops were used as follows: ryegrass (Lolium perenne L. in 2011/2012) and a mixture of winter oilseed-rape (Brassica napus ssp. oleifera var. biennis) and winter rye (Secale cereale L.) in 2012/2013 before pea; winter oilseed rape before potato and winter rye before barley. In Org II system composted cattle manure was also applied. In comparison with the control system, the winter cover crops, depending on plant species used, reduced the biomass and density of the weeds. In both years winter rye was a better suppressor of weeds than the other winter cover crops. Cover crops increased the yield of potato in rotation crops. When used together with composted cattle manure the cover crops caused significant yield increase in cereals.

Large-Leaved Lupin (Lupinus polyhyllus Lind.) and Early Red Clover (Trifolium pratense L.) as Green Manure Grops

Trials with large-leaved lupine (‘Lupi’) and early red clover (‘Jõgeva 433’) as green manure were carried out to study their suitability for green manure production. The trials were carried out on the trial fields of the Estonian University of Life Sciences in 2008-2010. Biomass production abilities of various plants grown with or without a cover crop were examined. In the experiment, different green manure crops with undersowing and pure sowing were compared for amounts of N, C, P, K and organic matter driven into soil and their effect on cereal yield. The value of these green manure crops as manure was estimated, based on their effect on the succeeding cereal yield. From green manure plants, sown with cover crops, red clover gave the best results, while large-leaved lupine was better grown as pure crop (18% more biomass than red clover in similar situation). Biomass from large-leaved lupine, grown without cover crop, was also the most efficient in returning nutrients into the soil. Pure green manure had bigger effect and it lasted longer if grown as undersowing. Lai noskaidrotu sugu piemērotību zaļmēslojumam, tika veikti pētījumi ar platlapu lupīnu (‘Lupi’) un agrīno sarkano āboliņu (‘Jogeva 433’). Izmēģinājumi tika iekārtoti Igaunijas dabas zinātņu universitātes pētījumu laukos 2008.-2010. gadā. Tika izvērtēta sugu spēja veidot biomasu, audzējot ar virsaugu un bez tā. Izmēģinājumā tika salīdzināti dažādi zaļmēslojuma augi gan pasējā, gan tīrsējā, izvērtējot augsnē atstāto N, C, P, K un organiskās vielas daudzumu un to ietekmi uz graudaugu ražu. Zaļmēslojuma vērtība tika noteikta, pamatojoties uz tā ietekmi uz nākamā gada graudaugu ražu. Izvērtējot zaļmēslojuma augus, kaļs sēti pasējā, labākie rezultāti tika iegūti, izmantojot sarkano āboliņu, bet platlapu lupīnai labāki rezultāti bija tīrsējā (par 18% lielāka biomasa nekā sarkanajam āboliņam līdzīgos apstākļos). Platlapu lupīnas biomasa, kas iegūta bez virsauga, visefektīvāk nodrošināja barības vielu papildināšanu augsnē. Lielāks un ilglaicīgās zaļmēslojuma efekts tika novērots, ja tas tika audzēts pasējā.

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.