Scientific registration n o : 319 Symposium n o : 20 Presentation: poster. DRAGOVIC Svetimir, MAKSIMOVIC Livija, KARAGIC Djura

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1 Scientific registration n o : 319 Symposium n o : 20 Presentation: poster Effect of long-term application of mineral or organic fertilizers on physical properties of loamy soil Effet de l'emploi systématique pendant plusieurs années d engrais minéraux ou organiques sur la qualité physique d un sol argileux DRAGOVIC Svetimir, MAKSIMOVIC Livija, KARAGIC Djura Institute of Field and Vegetable Crops, Maksima Gorkog 30, Novi Sad, Yugoslavia In 1996, we analyzed water-physical properties of a loamy soil in a long-term trial established in 1965 in order to study the effect of mineral fertilizers, plowed under harvest residues and stable manure on the yield of wheat, corn, sunflower and sugar beet which were rotated in a fixed order Mineral fertilization causes increases in bulk density while reducing total porosity, infiltration rate and the percentage of the structural aggregates mm in diameter. Similar effects were registered in the non-fertilized control plot. No large changes occurred in the variant with plowed under harvest residues in relation to the results of the analysis conducted in The application of stable manure affected positively all properties studied, especially bulk density and infiltration capacity. Introduction Various cultural practices are applied in order to increase plant yield. In addition to soil tillage, organic and mineral fertilization, plowing under of harvest residues and incorporation of other forms of organic matter are regular practices in the intensive agricultural production. Fertilizer application, as well as other cultural practices, affects not only plant yield but also physical soil properties. In the latter case, the effects may be positive and negative. If certain practices are applied inappropriately or untimely, they will negatively affect physical soil properties, first of all soil structure and water-air regimen. The intensive agricultural production calls for a regular study of water-physical soil properties, which are dynamic and subject to rapid changes. These properties should be analyzed after each application of cultural practices such as mineral or organic fertilization, etc. In Yugoslavia, those water-physical soil properties that are sensitive to mineral and organic fertilization or absence of fertilization are regularly studied, like in many other countries. Results have been reported in a number of papers. It has been found that physical soil properties change in dependence of prevailing conditions during and method of application of various cultural practices. Saric and Jocic (1993) recommend for mineral fertilization to be performed on the basis of soil fertility status because 1

2 excess amounts of mineral fertilizers may cause negative effects. Dragovic (1991) concluded that water-physical soil properties determine doses and ratios of mineral fertilizers, especially the coefficient of their utilization. Hadzic et al. (1993) reported that the repeated cultivation with heavy machines combined with mineral fertilization without organic fertilizers negatively affects physical soil properties. Dragovic and Maksimovic (1996) reported that the absence of organic fertilizers negatively affects physical soil properties in conditions of irrigation. This investigation was undertaken in order to establish the effect of a long-term organic and mineral fertilization of a rotation including several crops on the physical properties of a loamy chernozem soil. Material and Method A long-term trial was established in 1965 in northern Yugoslavia (the Vojvodina Province) on a loamy chernozem soil. The trial objective was to establish the effect of mineral and organic fertilizers on the yield of several crops in a rotation. In addition to the study of morphological characteristics and yields of the crops grown, water-physical soil properties were also monitored. In 1996, the following fertilization variants were analyzed: 1. Control non-fertilized; 2. Mineral fertilization, ; 3. Plowing under of harvest residues combined with mineral fertilization, ; 4. Organic fertilization, 40 t ha -1 of stable manure, in combination with mineral fertilization, N 70 P 60 K 40. The trial included the following crops: wheat, corn, sunflower and sugar beet. The crops were rotated in a fixed order. Organic fertilizers were added only to sugar beet and corn, mineral fertilizers to all crops. In variant 3, harvest residues are shredded, broadcasted over soil surface and plowed under; they are removed in the other variants. The soil is plowed at the depth of 30 cm; soil layers 0-15, and cm are analyzed. The previous analysis of physical soil properties was conducted in 1970 (Dragovic, 1973). Density and porosity Since the loamy soil has favorable and fairly stable physical properties, more or less intensive compaction occurred in all variants. Large increases in bulk density, especially in the surface soil layer, 0-15 cm, were registered in the control and the variant of mineral fertilization (Table 1). In relation to the previous analysis (Dragovic, 1973), there occurred an increase in bulk density in the surface soil layer of the unfertilized plot (14 %). In the variant with mineral fertilization, the increase was 6,3 %. The combination of organic and mineral fertilization (variant 4) kept the soil loose and there was no increase in bulk density. Increased soil compaction, i.e., increased bulk density, as a result of mineral fertilization had been reported before (Vucic, 1987; Zivkovic and Dragovic, 1975; Dragovic, 1991, etc.). Adding stable manure or harvest residues effectively prevents soil compaction. Soil compaction directly affects total porosity and air capacity. In our study, total porosity and air capacity were largely reduced in the variant of mineral fertilization 2

3 and control. It means that the water-air ratio, which is rather good in the chernozem soils, deteriorated. Bulk density Total porosity Table 1. Soil density and porosity Variant Depth Specific mass cm g cm -3 g cm -3 % vol 1. Ø-Control ,63 1,55 41, ,64 1,43 45, ,63 1,38 47,53 2,63 1,45 44,81 2. Mineral fertilizers 3. Harvest residues + 4. Stable manure + N 70 P 60 K ,61 2,63 2,61 2,60 2,61 2,58 2,60 2,60 1,52 1,43 1,44 1,46 1,41 1,38 1,37 1,39 1,34 1,36 1,33 1,34 Infiltration 41,76 45,42 45,25 44,14 46,18 47,13 47,30 47,86 48,06 48,09 48,85 48,33 F.W.C. % vol 37,20 35,77 33,88 35,62 38,03 36,68 35,91 36,87 36,40 35,56 33,81 35,25 35,59 34,62 32,42 34,21 Air capacity % vol 3,87 10,06 13,65 9,19 3,73 8,74 9,34 7,27 9,78 11,57 13,49 11,61 12,47 13,47 16,43 14,12 Infiltration rate depends on physical soil properties, plot condition at the time of the analysis, cultural practices applied, etc. In the case of clayey soils, according to Bosnjak (1992), the rate is determined by soil structure, stability of structural aggregates, soil fertility and the portion of organic matter in the soil. In this investigation, infiltration rate varied largely with fertilization method. In variants 1, 2, 3 and 4, the values of water absorption were 12, 65, 83 and 127 cm per 4 hours, respectively. In relation to the 1970 results, large reductions in infiltration rate occurred in variants 1 (non-fertilized) and 2 (mineral fertilizers). In variant 3, the rate was slightly reduced and in variant 4 (stable manure) the rate was considerably increased (Figure 1). Favorable effect of manure on infiltration rate has been reported by Reitmeir (cit. Vucic, 1964) as well as by other authors. Infiltration rate is also favorably affected by a combination of harvest residues and mineral fertilizers (Dragovic, 1968). Water conductivity Similarly to the other water-physical properties, water conductivity exhibits a range of reactions to a long-term application of various fertilizers combined with continual plant production. The values of water conductivity were somewhat reduced in the non-fertilized variant and the variant of mineral fertilization. In the variant with stable manure, conductivity was improved. However, the values of water conductivity were fairly uniform across the variants, similarly to the previous analysis (Dragovic, 1973). Other authors too reported that the water conductivity in chernozem ranges from 10-3 to 10-4 cm/sec (Vucic, 1964; Zivkovic and Dragovic, 1975; Miljkovic et al., 1980, etc.). 3

4 40 A Infiltration (cm) Infiltration (cm) Control NPK Harvest residuals+npk Stable manure+npk Hours B Hours Figure 1. Instantaneous (A) and cumulative (B) infiltration rate Table 2. Water conductivity Variant Sample depth, cm/sec Ø-Control 8,8*10-4 3,9*10-4 1,0*10-3 3,7* Mineral fertilizers 5,6*10-4 5,6*10-4 8,0*10-4 6,4* Harvest residues + 1,9*10-3 2,5*10-3 2,5*10-3 2,3* Stable manure + N 70 P 60 K 40 3,6*10-3 8,6*10-3 2,6*10-3 4,9*10-3 This investigation showed that the long-term application of mineral fertilizers does not cause large reductions in the values of water conductivity. Similar observations were made by Allamaras et al. (1985), Konstantinovic (1997), etc. These authors pointed out that the method and depth of soil tillage have a higher effect on water conductivity than mineral fertilization. Soil structure and stability of structural aggregates Structure analysis was done by sieving soil samples from the layer 0-30 cm through a series of sieved ranging in mesh size from 0.25 to 10 mm (Table 3). Percentage of structural aggregates determines water-air soil properties. The percentages determined in this round of analyses were similar to the previously obtained 4

5 results. In the non-fertilized variant and the variant of mineral fertilization, the percentages were reduced by 7 and 5 %, respectively, in the variant with harvest residues the percentage remained at the same level, and in the variant with stable manure it was increased by 2 %. Table 3. Soil structure aggregates dry sieving Variant Diameter of aggregates, mm structure % ,5 0,5-0,25 1. Ø-Control Mineral fertilizers Harvest residues Stable manure + N 70 P 60 K The reduction in the percentage of structural aggregates observed in the variant of mineral fertilization indicates that the soil is beginning to lose its positive characteristics, i.e., the process of soil degradation is at work. Only application of stable manure or other forms of organic matter can preserve favorable soil structure. Stability of structural aggregates was determined by wet sieving. The previous analysis (Dragovic, 1973) provided the values of %. The observed differences were small. Twenty-six years later, the stability was reduced by 9 % in the control variant, by 4-5 % in the other variants (Table 4). Table 4. Stability of structural aggregates Variant % aggregates, diameter in mm Total > ,5 0,5-0,25 1. Ø-Control 0,14 2,27 5,85 33,30 15,84 14,55 74,95 2. Mineral fertilizers 0,08 1,02 2,86 33,31 20,79 19,29 77,35 3. Harvest residues + 0,97 3,04 4,75 35,96 16,12 15,88 76,72 4. Stable manure + N 70 P 60 K 40 0,15 2,40 4,16 39,03 16,32 15,82 77,88 Chernozem has a high stability of structural aggregates, as stated by Vucic (1987) and a number of other authors. Itemizing the favorable physical properties of chernozem, Babovic (1997) points out the stability of structural aggregates when exposed to water. Conclusion The long-term trial with the application of various fertilizer forms showed that mineral fertilization tends to worsen some water-physical soil properties. Likewise, the absence of fertilization affected negatively these properties, especially the water-air regimen. The incorporation of stable manure not only maintained water-physical properties but also even tended to improve some less favorable properties. It reduced soil compaction and improved infiltration, filtration, soil structure and the stability of structural aggregates. 5

6 Literature Allmaras, R.R., R.H. Dowdy, Conservation tillage systems and their adaptation in United States. Soil Tillage Research, Vol. 5, No 2, Amsterdam. Babovic, D Determining soil structure and stability of aggregates. Methods of study and determination of physical soil properties, a monograph, pp Bosnjak, Dj Practice Book in Irrigation of Agricultural Crops. Faculty of Agriculture and Institute of Field and Vegetable Crops, Novi Sad, pp. 42. Dragovic, S Effect of plowing depth, fertilization and irrigation on physical properties of chernozem under a rotation of agricultural crops. M.Sc. thesis, Faculty of Agriculture, Novi Sad, pp.67. Dragovic, S The effect of applying harvest residues, stable manure and mineral fertilizers on physical properties of chernozem with and without irrigation. Soil and Plant, Vol. 22, pp Dragovic, S Effect of long-term application of mineral fertilizers on waterphysical properties of chernozem soil. Soil as a natural resource and a factor of development. Academy of Sciences and Arts of Bosnia and Herzegovina, Vol. 15, pp Dragovic, S., Livija Maksimovic Effects of irrigation on soil compaction and degradation. J. Contemporary Agr. Engineering, Novi Sad, Vol. 22, No 7, pp Hadzic, V., R. Nikolic, B. Marinkovic, D.Djukic Soil compaction causes and consequences. In: Effect of soil compaction on yield of agricultural crops, a monograph, chapter I, Faculty of Agriculture, Institute of Agr. Enginering, Novi Sad, pp. 98, Konstantinovic, J Soil Cultivation in Crop Production, Institute of Field and Vegetable Crops, Novi Sad, pp Miljkovic, N., V. Hadzic, B. Zivkovic, Z.. Milosev and S. Dragovic Hydraulic conductivity of hydromorphic and some other soils in Vojvodina. Soil and Plant, Belgrade, Vol. 29, 1, pp Saric, M., B. Jocic Biological potential of some cultivated plants in agrophytocenose depending on mineral nutrition. Serbian Academy of Sciences and Arts. a monograph, pp.135. Vucic, N Water properties of chernozem and hydromorphic black soil and their importance for the irrigation practice in the region of Backa. Contemporary Agriculture, No. 1, pp Vucic, N Water, air and thermal regimen of soil. A monograph, Vojvodina Academy of Sciences and Arts, Novi Sad, Vol. 1, pp Zivkovic, B., S. Dragovic Physical properties of soil at various depths and cultivation and fertilization methods. Proceedings of ILOMD Symposium, Keshetely - Hungary, pp Keywords : Long-term fertilization, bulk density, water retention, structural aggregates, infiltration, water conductivity. Mots clés : fertilisation, longue durée, densité apparente, rétention en eau, agrégats structuraux, infiltration, conductivité 6