1998 * IX * 2

A. Kanal.  
  Prof. Hans Nõmmik activities directed to development of soil chemistry 96
Prof. Hans Nõmmik activities directed to development of soil chemistry. It will soon be two years since the death of Hans Nõmmik, a man dedicated to science, and enamoured of his research and teaching work. H. Nõmmik, an agronomy doctor, professor and author of over 120 publications (see list in the main publication), was known throughout Scandinavia and the world as a prominent specialist in 15N-methods in soil-tree studies. Throughout his scientific life (last publication in 1995), he remained faithful to this topic in forestry soil science. In 1979 he was appointed to a professorship at Swedish University of Agricultural Sciences at Department of Soil Forestry in the field of forest fertilisation and soil chemistry. Since 1988 up to his death (†27.06.95) he was professor emeritus at the same department.

Hans was born in Tartu on March 5, 1922 in the family of professor Anton Nõmmik, who was the first head of Soil Science Department, established at Tartu University in 1919. Nõmmik junior received his base education at Treffner Gymnasium, but the final exams he took in Tallinn. In 1942 he started studies at agronomy faculty at Tartu University. In 1943 he emigrated to Sweden and in next year continued his broken studies at the Royal Swedish Agricultural Highschool, from where he graduated in 1946. Even when a student he began half-part time technician work at Department of General Agriculture. From that time until to the end of his life, his career, from junior researcher, throughout to docent and professor, was connected with research work. As a freshly graduated agronomist, he started research work at National Health Institute in Stockholm. In 1953, he defended his doctoral thesis, entitled `Fluorine in Swedish agricultural products, soil and drinking water` and was awarded the degree of doctor of agronomy in agricultural chemistry. The young doctor continued research work at Ultuna Agricultural Research Station, and worked on problems connected with nitrogen fertilisation, liming, pH and organic matter in agricultural soils. He conducted a range of field trials, of which the Ultuna Long-term Soil Organic Matter Experiment is still efficiently used for research (Kirchmann et al., 1994). Dr H. Nõmmik was honoured with a Kellogg’s Foundation scholarship to California University for three months in 1956. In 1962 he was obtained a docent title, but in several reasons he moved to the Forest Highschool in Stockholm taking the position of senior researcher. Another pioneering program started for him, which concerned fertilisation, acidification and liming of forest soils. Dr H. Nõmmik was a tireless and enthusiastic specialist in improving productivity of the Swedish forest. During work at Forest Highschool in Stockholm, he lectured at Umeå University and in courses for professional forestry specialists. His scientific activity and publications made him well-known even outside Europe, and he visited USA, Canada, South-Africa, India, Malaysia. In 1970 he was engaged as International Atomic Energy Agency expert-consultant in India. Hans Nõmmik was a delegate of World Soil Science Congress in 1964, 1968, 1974.

In 1979 when the Agricultural, Forestry and Veterinary Highschools were linked to Universitas, Prof. H. Nõmmik was elected from associated professor place to a permanent professor position at the Forestry Department. Finally his scientific endeavours were applied to teaching. The sulphur question in Swedish forestry was topical at that time, but he continued research on the biochemical cycling of nitrogen as well. In every institution where he worked, he was respected not only as specialist, but also as a colleague whose door was always open for a student or for a project leader. Prof. H. Nõmmik was a recipient of numerous awards, among the more eminent being the Bernstein prize from the Royal Swedish Academy of Forestry and Agriculture. Two eminent soil scientist Anton and Hans Nõmmik rest in Uppsala churchyard, but their scientific achievements and human intellect will long be remembered in Estonian agricultural sciences.

M. Agur.  
  The resistance analysis of potato varieties to potato virus M isolates (KVMEba, KVMEre) infection 104
The resistance analysis of potato varieties to potato virus M isolates (KVMEba, KVMEre) infection. The virological evaluation of potato varieties ‘Ants’, ‘Berber’, ‘Lazunak’, ‘Prigozii 2’, ‘Procura’, ‘Sante’, ‘Sarme’, ‘Timate’ and ‘Varajane kollane’ earlier analysed to PVX resistance has been continued. The complete resistance analysis of these varieties to PVM two isolates were carried out. The degree of susceptibility/resistance, the virus biosynthesis intensity and symptoms of infection in PVMEba and PVMEre inoculated plants (the first year) and in the plants of their tuber reproduction (the second year) have been determined in order to compare the reaction of potato varieties to the infection with different isolates of the same virus and to select out variety-virus isolate combinations more prospective for breeding to this virus resistance. The susceptibility/resistance of varieties studied to PVM depended on the virus isolate and the age of virus infection in plant. Var. ‘Prigozii 2’ has 100% susceptibility to both isolates and var. ‘Timate’ to PVMEre. The lowest degree of susceptibility to PVM was established in var. ‘Ants’ and ‘Procura’ to both isolates and in var. ‘Varajane kollane’ to PVMEre. The highest biosynthesis intensity of both isolates was determined in var. ‘Timate’. In var. ‘Procura’, ‘Ants’ and ‘Varajane kollane’ it was lower than in other varieties studied. Most of all varieties reacted to PVMEre with more severe symptoms than to PVMEba. In all combinations of variety and virus isolate the characteristics determined were higher in the plants of second generation (tuber reproduction) than in inoculated ones. The variety-virus isolate combinations with the degree of susceptibility less than 100% are recommended for using the clone selection to get the virus resistant material. Var. ‘Procura’, ‘Ants’ and ‘Varajane kollane’ are the most prospective for this purpose.
R. Kask.  
  A short account of the organic matter supplies in the main Estonian monarable soils 109
A short account of the organic matter supplies in the main Estonian nonarable soils1.
  1. The average characteristics of the organic matter supply in the organogenic horizon (Aorg) of Estonian nonarable soils may vary within the range of 55…890 t/ha. In automorphic soils those average characteristics decrease in the following order: typical sod-calcareous soils (on limestone and on morain) → leached sod-calcareous soils → podzolized sod-calcareous soils → sod-podzolic soils, ranging from 185…55 t/ha. In half-hydromorphic and hydromorphic soils the organic matter supply increases alongside with the increase of the degree of bogging in the following order: gleyed soils → soddy gley soils → peaty soddy gley soils → peaty gley soils → bog soils, ranging from 150…890 t/ha.
  2. The large differences in the organic matter supply of different soils does not inasmuch depend on the differences of the accumulation of organic matter in these soils as on the different intensity of the mineralization and leaching of the organic matter.
  3. At the calculation of the organic matter supply it is always necessary to consider the proportion of fine earth in the soil mass. As in Estonia it may vary from 0.5…100% the respective correction coefficient (0.005…1.00) should be applied.
H. Kärblane.  
  Leaching the plant nutrial elements applied by fertilizers 116
Leaching the plant nutrial elements applied by fertilizers. The leaching of plant nutrial elements (N, P, K) applied by fertilizers was investigated on sandy Podzol in the Antsla Experimental Station of the Estonian Research Institute of Agriculture.

The results of lysimeter experiments showed that the volume of leaching water through the 60 cm layer of soil makes 2.0…2.8% of the average annual precipitation (600 mm).

The lysimeter water from non-fertilized area contains 1.4…1.8 mg/l of N in nitrate form. The lysimeter water from area fertilized by mineral fertilizers contains up to 4.7 and by manure up to 4.0 mg/l N in nitrate form. The concentration of N-NO3 in the lysimeters of clover fields was 3.2 mg/l as an average. The lysimeter water from non-fertilized area contains 0.009 mg/l of phosphorus (P) and 6.2 mg/l of potassium (K). The figures from fertilized areas by mineral fertilizers were 0.017 and 15.9 mg/l accordingly.

In the case of application rate with ammoniumnitrate of 50…100 kg/ha N 0.21…1.00% N of applied was leached out in sandy soil. The leaching from the nitrogen of manure (50…100 t/ha) makes 0.05…0.62% and from symbiotically fixed nitrogen of clover 0.40…0.72%. In the case of application rate with potassium chloride of 75 kg/ha of K 0.95% of K was leached out. 0.09% and 0.09…0.13% of P was leached out from applied superphos-phate and manure accordingly.

R. Lillak.  
  The impact of date of the last cut and cutting frequency on productivity of alfalfa depending on cultivar characteristics 125
The impact of date of the last cut and cutting frequency on productivity of alfalfa depending on cultivar characteristics. As a result of unstable marine climate conditions, the growing of alfalfa connected with some risk, especially on light acid soils, very common for South-Estonia. For that reason 2-cut harvesting system was used in culti-vating of alfalfa. Growing of foreign alfalfa cultivars, exceeded local ones for faster development and recovery ability, make theoretically possible to transit from 2 to 3-cut harvesting system also in South-Estonian pedoclimatic conditions. However, surpassing for winter hardiness, as a rule, growing of these cultivars will increase the risk of deterioration the sward after few years. Under such circumstance's re-evaluation of cutting schedules of alfalfa sward is necessary. On the other hand there are different viewpoints for determining the optimum autumn harvesting data. Many Estonian grassland researchers are recommending farmers not to cut during the end of August and in September. The results of more resent experiments done in Experimental Station of Institute of Grassland Science and Botany, Estonian Agricultural University, suggest that duration of the ‘critical harvesting period’ could be much shorter.

The primary object of that study was to investigate the effect of the final cut and cutting frequency on relative DM yield of alfalfa, formation of botanical composition and density of the sward, and growing ability and number of tillers. Field experiment with two alfalfa cultivars (Swedish ‘Pondus’ and local ‘Karlu’) was established on loamy Podzoluvisol soil (content of organic matter in 0…20 cm soil layer was 2.80…3.20%, total nitrogen content – 0.14…0.15%, available potassium and phosphorus content – 74.3…86.9 and 45.4…50.1 mg/kg, respectively, and pHKCl – 6,2…6,4) on 22nd of May 1997. Two- and three-cut harvesting system with eight different data of the last cut (28.08…02.10) were used since 1996. The plants were harvest at a 8…10 cm stubble height. In loamy, lightly acid Podzoluvisol soil conditions of South-Estonia it's possible to use 3–cut harvesting system if winter hardy alfalfa cultivars with good recovery ability will be grown. Svalöf SW (Swedish) alfalfa variety ‘Pondus’ is one of the most perspective variety in that viewpoint. Very winter hardy local ‘Karlu’ is stopping to growth as early as in the middle of August and making possible only two cuts during vegetation period. When the 3-cut alfalfa harvesting system is using there are necessary to consider with ‘critical autumn period’. However, according with results of this investigation the length of critical period is much shorter than traditionally recommended in Estonia and limited with the end of August and first ten day's period in September. We are recommending farmers to make the last cut in the period 3 to 6 weeks before the end of vegetation period. The recommendation to harvesting in autumn 4…6 weeks before the first killing frost (-2.2 °C) is not always realizable (incl. 1996). Cutting alfalfa during the critical period resulted decreasing in DM yield from 10% (‘Karlu’) to 32% (‘Pondus’) in the next year. That decrease was resulted mostly by interfering with tiller production, not with number of tillers. Making 2 cuts (first cut at the 10% bloom stage) during vegetation period, the period before the final autumn cut was comparatively long (56…61 days). In such conditions the data of the last cut was not signifi-cant impact on the yield of the next year. The density of the sward correlated positively with the harvest frequency. However, the changes took place with sward density not reflected in the yielding ability of alfalfa as well as in the botanical composition of the sward. Data of the final cut have no influence on the sward density.

E. Must.  
  Efficiency of the milk cooling tanks of different firms 134
Efficiency of the milk cooling tanks of different firms. New milk cooling tanks, taken in to use in our farms cools milk quickly below of 4 °C. Therefore during cooling-storing, in case of milk transportation every day, in tanks the total bacterial count in milk changes not much, increases on an average 1.03 times. On the most cases tempera-ture of milk was at the end of the evening milking 4.1…9.6 °C, before the morning milking 2.7…4.3 °C and at the end of the morning milking 3.3…7.5 °C and milk cools down to the temperature of 4 °C within 0.1…0.5 hours. From these data be inferred, that new milk cooling tanks are of great importance in production low bacterial count milk.

According to ratio (quotient) of quality-cost are similar high effective Etscheid and Meko tanks KT and O (1.5), to these follows Alfa Laval HCA and CH (1.4) and Westfalia tanks (1.3). The lowest effeciency has RØ-KA Industrie tank RK (0.6).

To raise temperature of washing solution tanks firms Meko, Alfa Laval and Westfalia it is necessary to supply automaton cleaning units Meko, TWA 1000 R and Cryos Japy with the electric warming unit or take into use in addition the electric water heating unit for washing tank by heat water temperature of 80 °C.

E. Soovik.  
  The effect of drainage on the yield 143
The effect of drainage on the yield. The effect of drainage on the yield of arable rotation can be expressed and analysed by the dependence of the relative yield s on the relative drain spacing e (s = f(e)) according to formulae (1), (2) and (3), where unreduced due to excessive moisture yield s = 1 and drain spacing by the 1964 year instruc-tion e = 1. Formulae (4) and (5) present the first and second derivatives of the dependence s = f(e). These functions make possible to separate some characteristic stages of effect of drainage on the yield as it occurs from the Figure 1 giving ground to make several essential practical conclusions. Thus dependeces about the effect of drainage on the yield of arable crops present basis for seeking for optimal solutions in land drainage in Estonia.