Ilgalaikio tręšimo poveikis skirtingos kilmės dirvožemių biologiniam aktyvumui ; The long-term fertilization effect on biological activity of different genesis soils
LITHUANIAN UNIVERSITY OF AGRICULTURE Kristina Grigali ūnien ė THE LONG-TERM FERTILISATION EFFECT ON BIOLOGICAL ACTIVITY OF DIFFERNT GENESIS SOILS Summary of doctoral dissertation Biomedical sciencies, agronomy (06 B) Kaunas, 2005 The dissertation was prepared at Lithuanian University of Agriculture in 2000-2004. Scientific supervisor: prof. habil. dr. Zigmas Jonas Vaišvila (Lithuanian University of Agriculture, biomedical sciences, agronomy 06 B) Scientific consultant: assoc. prof. dr. Irena Danguol ė Zakarauskait ė (Lithuanian University of Agriculture, biomy 06 B) Council of Defence for Biomedical Sciences, Agronomy: Chairman: prof. habil. dr. Algirdas Juozas Motuzas (Lithuanian University of Agriculture, biomedical sciences, agronomy 06 B) Members: prof. habil. dr. Pavelas Duchovskis (Lithuanian Institute of Horticulture, biomedical sciences, agronomy 06 B) prof. habil. dr. Albinas Lugauskas (Institute of Botany, biomedical sciences, biology 01 B) dr. Sigitas Lazauskas (Lithuanian Institute of Agriculture, biomedical sciences, agronomy 06 B) assoc. prof. dr. Jonas Mažvila (Lithuanian Institute of Agriculture, biomedical sciences, agronomy 06 B) Official Opponents: prof. habil. dr. Edmundas Lapinskas (Lithuanian Institute of Agriculture, biomedical sciences, agronomy 06 B) dr.
Publié le : dimanche 1 janvier 2006
Lecture(s) : 47
Source : VDDB.LIBRARY.LT/FEDORA/GET/LT-ELABA-0001:E.02~2005~D_20060117_170123-78293/DS.005.1.01.ETD
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LITHUANIAN UNIVERSITY OF AGRICULTURE Kristina Grigali ū nien ė THE LONG-TERM FERTILISATION EFFECT ON BIOLOGICAL ACTIVITY OF DIFFERNT GENESIS SOILS Summary of doctoral dissertation Biomedical sciencies, agronomy (06 B) Kaunas, 2005
The dissertation was prepared at Lithuanian University of Agriculture in 2000-2004. Scientific supervisor: prof. habil. dr. Zigmas Jonas Vaivila (Lithuanian University of Agriculture, biomedical sciences, agronomy 06 B) Scientific consultant: assoc. prof. dr. Irena Danguol ė Zakarauskait ė (Lithuanian University of Agriculture, biomedical sciences, agronomy 06 B) Council of Defence for Biomedical Sciences, Agronomy: Chairman: prof. habil. dr. Algirdas Juozas Motuzas (Lithuanian University of Agriculture, biomedical sciences, agronomy 06 B) Members: prof. habil. dr. Pavelas Duchovskis (Lithuanian Institute of Horticulture, biomedical sciences, agronomy 06 B) prof. habil. dr. Albinas Lugauskas (Institute of Botany, biomedical sciences, biology 01 B) dr. Sigitas Lazauskas (Lithuanian Institute of Agriculture, biomedical sciences, agronomy 06 B) assoc. prof. dr. Jonas Mavila (Lithuanian Institute of Agriculture, biomedical sciences, agronomy 06 B) Official Opponents: prof. habil. dr. Edmundas Lapinskas (Lithuanian Institute of Agriculture, biomedical sciences, agronomy 06 B) dr. K ę stutis Armolaitis (Lithuanian Institute of Forestry, biomedical sciences, ecology and environmental 03 B) The official defence of the dissertation will be held at the public meeting of the Council of Defence for the Agronomy Science on 22 December 2005 at 10 a. m. at the lecture-room 322, Central Building of Lithuanian University of Agriculture. Address: Student ų str. 11, LT-53361, Akademija, Kaunas distr., Lithuania Summary of doctoral dissertation was distributed on 22 November 2005. The dissertation is available in the Libraries of the Lithuanian University of Agriculture and Lithuanian Institute of Agriculture.
5 LIETUVOS EM Ė S Ū KIO UNIVERSITETAS Kristina Grigali ū nien ė ILGALAIKIO TR Ę IMO POVEIKIS SKIRTINGOS KILM Ė S DIRVOEMI Ų BIOLOGINIAM AKTYVUMUI
Daktaro disertacijos santrauka Biomedicinos mokslai, agronomija (06 B) Kaunas, 2005
6 Disertacija parengta 2000-2004 metais Lietuvos em ė s ū kio universiteto Agronomijos falkulteto Dirvotyros ir agrochemijos katedroje. Mokslinis vadovas: prof. habil. dr. Zigmas Jonas Vaivila (Lietuvos em ė s ū kio universitetas, biomedicinos mokslai, agronomija - 06B); Mokslinis konsultantas: doc. dr. Irena Danguol ė Zakarauskait ė (Lietuvos em ė s ū kio universitetas, biomedicinos mokslai, agronomija - 06B)
Disertacija ginama Lietuvos em ė s ū kio universiteto Agronomijos mokslo krypties taryboje: Pirmininkas prof. habil. dr. Algirdas Juozas Motuzas (Lietuvos em ė s ū kio universitetas, biomedicinos mokslai, agronomija - 06B) Nariai: prof. habil. dr. Pavelas Duchovskis (Lietuvos sodininkyst ė s ir darininkyst ė s institutas, biomedicinos mokslai, agronomija - 06B) prof. habil. dr. Albinas Lugauskas, (Botanikos institutas, biomedicinos mokslai, biologija 01 B), dr. Sigitas Lazauskas (Lietuvos emdirbyst ė s institutas, biomedicinos mokslai, agronomija 06 B) doc. dr. Jonas Mavila (Lietuvos emdirbyst ė s institutas, biomedicinos mokslai, agronomija 06 B) Oponentai: prof. habil. dr. Edmundas Lapinskas (Lietuvos emdirbyst ė s institutas, biomedicinos mokslai, agronomija 06 B) dr. K ę stutis Armolaitis (Lietuvos mik ų institutas, biomedicinos mokslai ekologija ir aplinkotyra 03B) Disertacija bus ginama vieame Agronomijos mokslo krypties tarybos pos ė dyje, kuris vyks 2005 m. gruodio 22 d. 10 val. Lietuvos em ė s ū kio universiteto centrini ų r ū m ų 322 auditorijoje. Adresas: Lietuvos em ė s ū kio universitetas, Student ų g. 11, LT-53361, Akademija, Kauno raj., Lietuva. Disertacij ą galima susipainti Lietuvos em ė s ū kio universiteto ir Lietuvos emdirbyst ė s instituto bibliotekose.
7 INTRODUCTION Relevance of the subject. Present days concern regarding the long-term productivity and sustainability of agro-ecosystems is leading to the development and protection of soil resources (Kanchikerimath et al., 2001). Soil is not only the main implement of agricultural production, but also the habitat of plants and microorganisms and the basis for nutrition processes. Soil fertility is formed through the interaction of complex natural and anthropogenic processes (Kandeler et al., 1993). Decomposition of plant residues and synthesis of humic substances are largely dependent on soil biological activity ( Берестецкий , 1984). As a result, determination of the changes in soil biological activity and composition of microorganisms is a very important criterion seeking to estimate ecological value of long-term fertilization trials (Svirskiene, 2003; Христенко ir kt., 2001; Bandick ir kt., 1999). Up-to-date agriculture cannot be visualised without the use of mineral and organic fertilizers, which in turn, raises a question of how the fertilizers used affect the soil and biological processes occurring in it. Rational soil fertilization with organic and mineral fertilizers improves microbiological and biochemical soil properties and promotes enhancement of agricultural crops yield (Svirskien ė , 1999; Звягинцев , 1980). Many researchers have noted the positive effect of low nitrogen, phosphorus, and potassium rates, especially, when using them systematically or when combining with organic fertilizers on soil biological activity (Svirskien ė et al., 1995; Marschner et al., 2003). However, some data found in literature suggest that even low rates of mineral fertilizers when used systematically for a long time have a negative effect on soil biological and other properties (Svirskien ė , 1995). Soil enzymes, released by microorganisms, roots and mesofauna and absorbed by soil colloids, are active catalysts of biochemical processes that determine their intensity and singleness; consequently their activity is an important indicator of the total biological activity and productivity ( Беспалова , 1984; Алиев , 1987). The enzymes sacharase and urease are considered to be objective indicators of soil fertility ( Русин et al., 1983). Some research has already been done (Arlauskien ė , 1997, 1998, 1999; Svirskien ė et al., 1995, 1997, 1999, 2003) on the effects of fertilization on soil biological activity, however, the findings are often not linked to soil genesis, soil texture, chemical properties, and crops grown and are limited by only short-term fertilizer application. Experimental objective : to determine effect of organic and mineral fertilizers on biological activity of different genesis soils in long-term crop rotation trials. Experimental tasks: • to determine biological activity of different genesis soils; • to identify the relationship between soil biological activity and chemical properties; • to study the effect of organic and mineral fertilizers and their combinations on soil biological activity; • to investigate the effect of mineral fertilizers on biological activity of different genesis soils; • to find out the correlation between the productivity of crops grown in the crop rotation and soil biological activity. Experimental object : Soil biological activity investigated according to the activity of the enzymes urease, sacharase, alkaline phosphatase, arylsulfatase, dehydrogenases and respiration intensity in long-term fertilization trials. Novelty of the research work. It is the first time complex research has been done on the effects of fertilization on soil biological activity that formed on limnoglacial, moraine and abrubt textural change genesis. Biological activity was investigated in relation to soil genesis and chemical properties. The relationship between the crops grown, their yield and enzyme activity and respiration intensity in the soil was identified. It is the first time activity of
8 enzymes such as dehydrogenases, alkaline phosphatase and arylsulfatase, has been studied in the soils of Lithuania. Practical relevance of the work. The data substantiated by the new research supplement the knowledge on the effects of various intensity plant fertilizations with organic and mineral fertilizers on soil biological properties. The determination range of enzymes in Lithuanian soils was expanded. It is expedient to determine the activity of dehydrogenases, alkaline phosphatase and arylsulfatase in further research, since they are good indicators of microbiological activity and phosphorus and sulphur circulation. Approbation of the dissertation. The research data were published in scientific works Vagos (2001), Agriculture (2003); Agricultural sciences (2003), Roczniki gleboznawcze in Poland (2004); research results were reported at the scientific conferences: international Soil in the Environment in Krakow (2003) and Achievements and Tasks of Soil Science and Plant Nutrition in Course of Integration into the EU at LUA; conferences Lithuanian biological diversity (condition, structure, protection) (2001, 2003) at VPU, Human and nature safety (2001) and Youth seeks progress (2001) at LUA. The volume of the dissertation. The work is written in Lithuanian, it consists of 102 pages, 34 tables, 10 figures and 150 references are used in the dissertation. EXPERIMENTAL CONDITIONS AND METHODS Soils and sites of experiments. Soil of LUA Experimental station (Kaunas distr.) is with abrubt textural change. In Ap horizon of soil prevails silt fraction (54.7%), a lower amount (29.8%) of sand, whereas in subsoil significantly increased amount of sand (56.3%) and decreased amount of silt fraction (20.9%). In deeper horizons (50 cm and deeper) dominated moraine clay. Soil pH of Ap horizon is neutral or alkaline, has moderate (2.3%) amount of humus, total nitrogen 0,12%, available phosphorus 75 mg kg -1 and available potassium 90 mg kg -1 . Soil is with abrubt textural change silty loam on moraine clay Calcari-Epihypogleyic Luvisol, in the text silty loam on moraine clay Luvisol . Kri ū kai (akiai distr.). In soil prevails limnoglacial silty loamy and has no skeleton. In Ap horizon of soil dominates silt fraction (69.9%), lower amount (17%) of clay and (12.9%) sand fractions. Soil pH of Ap horizon was alkaline, has moderate (2.4%) amount of humus, total nitrogen 0,12%, available phosphorus 82 mg kg -1 and available potassium 84 mg kg -1 . Soil is limnoglacial silty loamy Endocalcari-Epihypogleyic Cambisol, in the text limnoglacial silty loamy Cambisol . Sk ė miai (Radvilikis distr.). Soil developed on moraine deposits and has lighter texture. In Ap horizon dominated sand fraction (54.7%), lower amounts of silt (31.2%) and (14.1%) clay fractions. Soil pH of Ap horizon was alkaline (pH 7.4), has moderate amount of humus, total nitrogen 0,17%, available phosphorus 57 mg kg -1 and available potassium 109 mg kg -1 . Soil is moraine sandy loamy Epicalcari-Endohypogleyic Cambisol, in the text moraine sandy loamy Cambisol . Scheme of the experiment. Two long-term fertilization trials were established in 1966 at LUA Experimental station (Kaunas district): I trial used mineral fertilizers and II trial organic and mineral fertilizers. Two long-term fertilization trials carried out by workers of Centre Agrochemical Investigations at LIA: one was established in 1971 at Sk ė miai (Radvilikis district) and second in 1990 at Kri ū kai (akiai district). In the period of 1999-2002 was grown in trials: LUA Experimental station fodder beet -spring barley - one year perennial grasses - winter wheat, Sk ė miai sugar beet - spring barley - annual grasses (vetch-oats mixture for green forage) - winter wheat, Kri ū kai potatoes -spring barley - annual grasses - winter wheat. The following mineral fertilizers of the same forms were used in trials: ammonium saltpetre, granulated superphosphate, potassium chloride. Fertilizers of nitrogen, phosphorus
9 and kallium were used in spring. Farmyard manure was spread and ploughed in autumn before fodder beet. Average rates of fertilizers per crop rotation were given in 2-7 tables. Agriculture crops yield calculated as metabolizable energy (MEY) GJ ha -1 (Jankauskas et al., 1999). Suitable varieties of agriculture crops in the Lithuania were grown in the trials. Meteorological conditions. A thermal and irrigation condition in the period of plants vegetation was described by one of the most informative agrometeorological indicates G. Selianinovo hydrothermal coefficient (Bukantis, 1998). LUA Experimental station. In 1999, 2000 and 2002 dominated optimal (HTC=1.0-1.4), 2001 rather wet (HTC=1.6) hydrothermal condition. The first part of 1999 and second part of 2002 was dry. Radvilikis distr. Sk ė miai . In 1999 and 2000 dominated rather wet (HTC=1.7-1.8), 2001 optimal hydrothermal condition and in 2002 was weak dry (HTC=0.8). Methods of investigations. Soil samples were taken three times each year in the growing season: first time before fertilization, second 2-3 weeks after fertilization and last after the harvest, from 0-20 cm depth. The analyses of soil biological activity were determined on air-dried samples by following methods: sacharase (invertase) by Hofman ir Seegerer (1950) and urease by Hofman ir Schmid (1953), modified by Chunderova (1973); dehydrogenases was based on 2.3.5 triphenyltetrasol chloride colourless oxidized form reaction to red formasane (Methodical..., 1978); alkaline phosphatase by Schinner et al.; arylsulfase by Tabatabai et al.; soil respiration intensity by Öhlinger (Schinner et al., 1995). The total biological activity evaluated relatively by summation of urease, sacharase and dehydrogenases activity and soil respiration intensity, by Acci method, modified by Kariagina (1983). Soil chemical analyses carried out by methods: soil pH potentiometric method; available phosphorus and potassium by A-L method; organic carbon by Tyurin method (modified by Nikitin (1999)); total nitrogen Kjeldahl method; mineral nitrogen distillation and colorimetric (1 N KCl extraction) method. Data of experiment was evaluated by methods of onefactorial disperse analysis (ANOVA). Dependence of mineral fertilizers and soil chemical properties on soil biological activity was processed by correlative - regressive analysis. Relationship was calculated among agriculture crop yield and soil biological activity. For calculation correlative regressive analysis was used second level equation y = a + bx + cx 2 and coefficient η (STAT ENG) (Tarakanovas et al., 2003). The significances of differences in correlative regressive analyse was used t Student test. Data reliability significant at the probability 95% level marked * and 99% level **. EXPERIMENTAL RESULTS AND DISCUSSION Comparison of biological activity in the soils of different genesis Soil group, genesis and texture affect soil biological activity. Urease activity was found to be the highest in limnoglacial silty loamy Cambisol compared with moraine sandy loamy Cambisol and silty loam on moraine clay Luvisol (Table 1) . This soil is markedly dominated by silt fraction (69.9%), had higher organic carbon content. The activity of sacharase and arylsulfatase was significantly higher in moraine sandy loamy Cambisol . This soil was dominated by sand (2-0.05 mm particles) fraction (54.7%), had lower organic carbon content and the lowest pH value (6.3-6.9), compared with the other soils. This was determined by the fact that optimal pH is more acidic for the activity of these enzymes. Dehydrogenases activity and soil respiration intensity were higher in limnoglacial silty and moraine sandy loamy Cambisol s. Dehydrogenases activity was almost a twice as high as that of silty loam on moraine clay Luvisol . In this case not only soil texture and genesis, but also its chemical properties, especially organic carbon content, had an impact.
10 Table 1. Biological activity in the soils of different genesis Urease Sacharase DehydrogenSoil reiation + Alkaline + Arylsulfatas insitprphosphatase pmegr 2N4H h 3 mpg egr l4u8c ohs e foaprseemr sa2 s4ma gnh e CtOe 2 npser y2 4m gh μ g ph3e nh ol per nitpreoer p μ h1g e hn ol Silty loam on moraine clay Luvisol 0,19 18,10 3,17 0,25 328 55 Limnoglacial silty loamy Cambisol 0,45 20,07 6,51 0,28 316 40 Moraine sandy loamy Cambisol 0,34 28,99 6,70 0,29 268 84 Note: per 1 g of air-dried soil, + one-year data of investigations Alkaline phosphatase activity was higher in silty loam on moraine clay Luvisol and limnoglacial silty loamy Cambisol , compared with moraine sandy loamy Cambisol . The obtained results suggest that alkaline phosphatase activity was to a greater extent influenced by soil pH or available phosphorus content rather than by soil genesis. Soil biological activity in relation to soil chemical properties Soil is a solid biological system in which indicators of biological activity are closely related to chemical properties. The dependence of biological activity on soil chemical properties was more evident in silty loamy soils compared with sandy loamy. In silty loam on moraine clay Luvisol , having fertilized the plants with only mineral fertilizers, the activity of urease significantly depended on the total nitrogen ( η =0,92*), and that of dehydrogenases ( η =0.94*) on the content of available potassium in the soil. Having fertilized the plants with organic and mineral fertilizers (trial II), a strong correlation was determined between sacharase activity and total nitrogen ( η =0.82*) and pH value ( η =0.78*), as well as between organic carbon and dehydrogenases activity ( η =0.94*) and respiration intensity ( η =0.86*) in the soil. In limnoglacial silty loamy Cambisol a very strong relationship was identified between urease activity and available phosphorus ( η =0.70*), a weaker relationship was found with organic carbon contents ( η =0.60) and pH value ( η =0.63). Soil respiration intensity significantly ( η =0.85*) depended on organic carbon content. In moraine sandy loamy Cambisol , biological activity was little dependent on soil chemical properties. Only soil respiration intensity significantly ( η =0.59*) depended on soil pH value. Phosphatase activity strongly ( η =0.78-0.93*) correlated with available phosphorus in all three soils. A strong relationship ( η =0.83-0.87*) between arylsulfatase activity and available potassium contents was identified in silty and sandy loamy Cambisol s. Alkaline phosphatase activity and arylsulfatase activity decreased when respectively increased amounts of available phosphorus and potassium in soil. Dehydrogenases activity and respiration intensity were more dependent on organic carbon content in the tested soils. In silty loam on moraine clay Luvisol and limnoglacial silty loamy Cambisol , which contained more organic carbon, higher respiration intensity was determined compared with moraine sandy loamy Cambisol . This suggests that more intensive respiration occurring in these soils results in a more rapid mineralization of organic matter. The effects of long-term fertilization with mineral or organic fertilizers and their combinations on soil biological activity Organic and mineral fertilizers significantly (30%) increased urease activity, which characterises nitrogen regime in silty loam on moraine clay Luvisol (Table 2). Urease activity
11 1 was mostly increased (53%, 42% and 42%) by N 78,8 P 50 K 75 , 100 t ha -1 and 50 t ha - manure + P 32,5 applied annually per rotation. Table 2 . The effects of mineral or organic fertilizers and their combinations on soil biological activity LUA Experimental station, Kaunas distr., average 1999-2002 Urease mg Sacharase Dehydrogenases Soil respiration Treatments NH 3 per 24 mg glucose mg formasane per intensity mg CO 2 h per 48 h 24 h per 24 h Unfertilized 0,19 18,39 3,53 0,23 50 t ha -1 manure per 0,23 17,55 0,25 rotation 3,79 100 t ha -1 manure per 0,27 18,43 0,26 rotation 4,95 N 78,8 P 50 K 75 0,29 19,51 4,30 0,27 N 37,5 P 40 K 75 0,24 17,04 4,01 0,22 N 120 P 65 K 90 0,23 17,53 3,43 0,23 50 t ha -1 e pe 0,27 18,40 0,25 manur r rotation + P 32 5 , annually 3,76 50 t ha -1 manure per 0,25 16,99 0,24 rotation +N 37,5 P 40 K 75 annually 4,12 LSD 05 0,05 2,45 0,77 0,03 Note: per 1 g of air-dried soil Sacharase activity was the lowest in 1999 compared with the other experimental years. The first half of summer was droughty (HTC=0.1-0.4). Under such conditions manure and mineral fertilizers affected sacharase activity insignificantly. After a year sacharase activity resulting from these fertilizers was significantly higher than a year before. Mineral fertilizers applied to perennial grasses and winter wheat as well as the effect of manure of the second and third year did not increase sacharase activity in the soil. Having summarised averaged data from four years we can assert that positive effect of mineral and organic fertilizers on sacharase activity was not revealed. Farmyard manure incorporated ones per four years insufficiently increased soil humus content, which is related to sacharase activity. Dehydrogenases activity reflects the total activity of soil microflora. Manure and mineral fertilizers increased dehydrogenases activity annually. Only when winter wheat was grown in the trial, dehydrogenases activity in many cases was promoted by the effect of manure, whereas mineral fertilizers either suppressed its activity or did not have any significant effect on it. Dehydrogenases activity was mostly enhanced by 100 t h -1 e nd average annual a manur a N 78,8 P 50 K 75 fertilizer rates per rotation by 40% and 22%, respectively. Alkaline phosphatase is an inductive enzyme whose activity is enhanced at low phosphorus content in the soil. Plant fertilization with organic and mineral fertilizers inappreciably changed the activity of alkaline phosphatase. The activity of alkaline phosphatase was promoted (7.6%) only by 100 t ha -1 manure rate incorporated for the preceding crop. Arylsulfatase activity is important for the breakdown of sulphur compounds in the soil. Arylsulfatase activity did not significantly change through organic and mineral fertilizer rates, although under the effect of 100 t ha -1 manure rate, the activity of this enzyme was slightly higher (16%) than in the soil of control treatment.
12 Soil respiration intensity was increased by mineral and organic fertilization only in the years when fodder beet and winter wheat were grown, whereas in the years when spring barley and perennial grasses were grown, soil respiration intensity was suppressed. Averaged experimental data suggest that these fertilizers and their combinations promoted soil respiration intensity (Table 2). In all experimental treatments where fodder beet was applied with manure, an increase in soil respiration intensity was identified compared with unfertilized treatment. Soil respiration intensity was also increased by average N 78,8 P 50 K 75 fertilizer rate per crop rotation. % 25 20 15 10 5 0 2 3 4 5 6 7 8 Treatments Fig. 1. The effects of mineral or organic fertilizers and their combinations on the changes of total biological activity (values of treatments are shown in table 2) Having compared organic and mineral fertilizer rates, equivalent in terms of nutrients, it was found that nutrients applied with organic fertilizers (100 t ha -1 manure) per rotation increased biological activity in the soil more than the nutrients applied with mineral fertilizers (N 120 P 65 K 90 ). However, comparison of 50 t ha -1 manure and N 37,5 P 40 K 75 rates showed a similar biological activity. This organic fertilizer rate incorporated every four years was too low to reveal the difference of its efficacy, compared with the equivalent mineral fertilizer rate. Total biological activity. Considering soil as undivided biological system in which biological, chemical and physical properties are closely related, it is important to identify changes in the total biological activity in the soil occurring under the effects of mineral or organic fertilization (Fig. 1). Manure and mineral fertilizers and their combinations increased biological activity in the soil from 3 to 24%. The total biological activity in the soil was mostly promoted by moderate annual (N 78,8 P 50 K 75 ) mineral fertilizer rates and 100 t ha -1 manure rate designed for fodder beet fertilization. The effect of long-term fertilization with mineral fertilizers on soil biological activity Urease activity. Plant fertilization with only mineral fertilizer rates had little effect on promoting urease activity in silty loam on moraine clay Luvisol (Table 3). A significant increase of urease activity in the soil was determined to have resulted from the application of average N 75 P 65 K 75 fertilizer rate per rotation. Analogous rates of one-component or two-component fertilizer did not have significant effect on urease activity. In limnoglacial silty loamy Cambisol , having fertilized potatoes and winter wheat with mineral fertilizers, urease activity declined (Table 4). In the years of annual grasses and barley growing urease activity was increased more (23%) by N 120 P 180 K 180 fertilizer rate. Averaged data from four years indicate that mineral NPK fertilizers did not have any significant effect on urease activity. Only trends of changes in urease activity were identified under the effect of fertilizers. In moraine sandy loamy Cambisol a significant trend of urease activity suppression under the effect of fertilizers was determined, especially under the effect of high nitrogen and phosphorus fertilizer rates, in the plots grown with sugar beets, barley and winter wheat. Only in 2001 in the plots with annual grasses mineral fertilizers promoted urease activity in the soil. Average of experimental data suggests that there were no significant differences in urease activity under the effect of mineral fertilizers (Table 5). In the soil of the trial plots that were fertilized with moderate mineral fertilizer rates urease activity was slightly higher than in unfertilized plot. However, high rates (N 135 , P 180 , K 180 ) tended to suppress urease activity.
13 Table 4 . The effects of mineral fertilizers on soil biological activity in silty loam on moraine clay Luvisol LUA Experimental station, Kaunas distr., average 1999-2002 TreatmenUrease mg mSga cglhuacraossee Dehydrogenases mg Soil respiration CO 2 per ts NH 3 per 24 h per 48 h formasane per 24 h intensity 24m gh Unfertiliz 0.18 17.83 2.81 0.27 ed N 75 0.20 20.32 3.42 0.27 P 65 0.18 19.38 3.46 0.27 K 75 0.19 20.01 3.96 0.28 P 65 K 75 0.18 18.69 4.18 0.26 N 75 P 65 0.19 19.57 4.01 0.27 N 75 K 75 0.19 21.73 4.05 0.24 N 75 P 65 K 75 0.21 20.46 4.13 0.25 LSD 05 0.03 3.11 0.66 0.04 Note: per 1 g of air-dried soil Sacharase activity. In silty loam on moraine clay Luvisol mineral fertilizers increased sacharase activity by on average 12%, compared with unfertilized plot. The highest increase in the activity of this enzyme resulted from the application of N 75 K 75 and N 75 P 65 K 75 fertilizer rates per rotation (Table 3). In limnoglacial silty loamy Cambisol , when was grown potatoes and barley, mineral fertilizers increased sacharase activity in the soil of most treatments. However, in the trial grown with annual grasses and winter wheat, mineral fertilizers suppressed the activity of this enzyme. Averaged data from the 1999-2002 period suggest that long-term crop fertilization with various rates of mineral fertilizers suppressed (2-12%) sacharase activity. However, a significant reduction (12%) in sacharase activity in the soil was identified only in the treatment where the plants were applied with N 67.5 P 90 K 180 fertilizer rate. Table 5. The effects of mineral fertilizers on soil biological activity in limnoglacial silty loamy Cambisol Kri ū kai, akiai distr., average 1999-2002 mg formasane intens Treatments Ureasem gh glSuaccohsaer apseer m48g Dehydrogenases Soilp eirtre ys2 p4mi rgha tiCoOn 2 NH 3 per 24 h per 24 h Unfertilized 0.45 20.07 6.51 0.28 P 90 K 90 0.43 19.01 5.63 0.24 N 67,5 K 90 0.45 17.95 6.21 0.21 N 67,5 P 90 0.43 19.20 5.36 0.26 N 67,5 P 90 K 90 0.44 18.09 5.42 0.25 67,5 P 180 K 90 0.42 N 19.28 5.05 0.28 N 67,5 P 90 K 180 0.44 17.66 5.51 0.25 N 135 P 180 K 90 0.45 19.72 5.50 0.24 N 135 P 90 K 180 0.45 18.86 5.65 0.22 N 135 P 180 K 180 0.47 18.78 5.23 0.22 LSD 05 0.05 2.37 0.77 0.04 Note: per 1 g of air-dried soil
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