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3. Doktoritööd

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/2490

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Sirvi 3. Doktoritööd Märksõna "agricultural land" järgi

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    Land use and soil management in Estonian agriculture during the transition from the Soviet period to the EU and its current optimisation by the spatial agro-economic decision support system
    (Eesti Maaülikool, 2007) Astover, Alar
    According to the main objectives of the study, the following conclusions could be presented: 1. The drastic decrease in arable land use in the transition to a free market economy continued until EU CAP was implemented in Estonia. The regional differences in land use changes in the 1990s were determined mainly by local bio-physical disadvantages such as soil quality. The higher decrease rate of arable land use in 1992– 2001 occurred in the regions with low soil fertility. A decrease in soil fertility by one quality point brings about a 2.5% increase in the proportion of abandoned land. The loss of subsidies at the beginning of the transition period highlighted the importance of pedo-climatic conditions in the formation of the profitability of agricultural production but the EU agricultural policy has again relieved the impact of bio-physical diversity on the competitiveness of agriculture. 2. Plant nutrient balances of Estonian arable soils were analysed in the long-term (1939–2003) with uniform methodology. This approach enabled the evaluation of some aspects of sustainability of agricultural land use and soil management through transition from the Soviet era to the open market economy. The application of both mineral and organic fertilisers started to increase in the 1960s and peaked in the 1980s. The increase in fertilisation was not followed proportionately by yield increase and this resulted in positive NPK balances of arable soils in the 1970–1980s, which has significantly improved the nutrient supply of arable soils. The quantities of plant nutrients N, K and P applied to the fields exceeded the amounts removed through crop harvesting by a factor of 2–2.3 (N), 1.9–2.2 (K) and 3–3.5 (P). The amounts of lactate soluble P and K increased by 1.1 and 0.7 mg kg-1 soil per year, respectively. 3. In the 1990s the use of fertilisers has decreased by significant factors: N by six; P by twenty; K by thirty and organic fertilisers by four. The total balances of K and P of arable soils have become negative as a consequence of inadequate fertilisation. Active balance, which enables the estimation of the degree to which formation of the yield occurs at the expense of soil resources, shows that at present the 58 59 largest deficiency is regarding P (68%) and K (57%) followed by N (34%). Thus, at present, crop production takes place largely at the expense of the soil nutrient reserves created by farmers in the 1970–1980s. The use of mineral fertilisers is less intensive in the regions with low soil quality. Decrease in soil fertility reduces the amount of mineral fertilisers used by 2.85 kg NPK per one soil quality point. As nutrient deficiency is highest for forage crops, the depletion of soil P and K may become critical, especially in organic systems where grasslands are dominant. Agri-environmental policy should more consider soil degradation due to the negative plant nutrient balances of arable soils in Estonia. 4. At present only 40–50% of the yield potential of cereals is realised in actual farming conditions. The high yield gap indicates the ineffective use of pedo-climatic resources and this causes agricultural self-sufficiency at the national level to deteriorate. Low realisation of yield potential of cereals is partly due to the insufficient use of fertilisers, as the actual yield level is limited by low input of plant nutrients to the soil. It must, therefore, be considered that the yield formation of cere - als is largely determined by the pedo-climatic conditions (50–60%), and that fertilisers are a lesser influence. In the case of oilseed rape the utilisation of the yield potential is 60–65%, which is induced by more intensive fertilisation compared to cereals. To narrow the yield gap in a profitable and environmentally friendly way, the field-specific fertiliser and other input optimisation is required. 5. A positive effect of the collapse of Estonian agriculture has been a reduction of the pressure on the environment whereas a negative effect to the several aspects of sustainable agriculture has emerged (i) in soil degradation which is due to insufficient investments into maintaining soil fertility, (ii) in ineffective use of pedo-climatic resources, (iii) in low profitability and competitiveness of the agri - culture sector, and (iv) in decreased national food supply. To achieve more sustainable agriculture the optimisation of agricultural land use and soil management should be based on the scientific knowl - edge and from this necessary precondition to develop a spatial agro-economic DSS. 6. The agronomic models for spring barley and potato, based on the regression analysis of numerous field experiments, were developed to assess the impact of soil and climate conditions on the effective - ness of fertilisers. The effectiveness of fertilisation depends, to a large extent on, besides soil properties, meteorological conditions. The variance of the average effectiveness, even of quite small rates, of mineral fertilisers (N60, P26 and K50) is very high. Higher efficiency is guaranteed in the case of balanced fertilisation but the optimum combination of nutrients depends on the relative prices of fertilisers and yield. The developed models enable the estimation of the pedo-climatic and economic risks in fertilisation optimisation. Improved agronomic models operating in spatial and temporal scale are forming a basis for knowledge-based DSS. 7. Data handling and presentation in the agricultural decision making process was for the first time in Estonia embedded to fieldspecific GIS and its application possibilities were analysed in the example of Kullamaa rural municipality. A field-specific database was compiled and agro-economic models were applied to provide information for decision makers. Economically effective N norm for barley is, in most of the study area, from 50 to 60 kg N ha-1 but on a quarter of arable land in the study area it is uneconomical to apply N to barley. Field-specific fertiliser optimisation compared to uniform fertiliser application can help farmers to avoid economic losses and simultaneously increase effectiveness of fertilisation and low yields. The simulated barley yield for the study area is, with the use of economically optimised amounts of NPK fertilisers, 2.6 Mg ha-1, which is by 1.1 Mg ha-1 higher compared to the actual cereal yield in the region. Composed thematic maps enable the clear presentation of spatial variability in the profitability of barley production from field to region scale. Farmers can use spatial profitability data with other criteria for crop rotation planning and for strategic decisions but presented DSS does not make decisions, but rather contributes knowledge that can be used in the decision making process. The ben - efit of this DSS is that information from different sources is collected, processed and integrated into a unified system which makes decision making more effective. This also makes existing soil information more easily available and self-explanatory for stakeholders. 8. Despite the fact that this study presents spatial agro-economic DSS on the example of just one rural municipality and a single crop, its importance is more extensive. Up-scaling the modelling results 60 61 from field-level also enables its application in regional planning and in macro-economic analysis. In this study the methodology for the functioning of the DSS was developed which is further applicable nationwide. There is an increasing demand for the planning of abandoned agricultural land in Estonia and a developed DSS can be expanded for the cultivation of bioenergetic crops or for afforestation of abandoned land. 9. Further improvement of DSS should focus on the development of agronomic models for various crops and economic models should be continuously adjusted according the changes in socio-economic conditions. The database of digital soil map should be definitely appended with quantitative parameters, which would provide prerequisites for its more extensive applications such as related production activities to environmental impact. The extensification of Estonian agriculture during the transition period has reduced the negative impact on the environment but at the same time this has caused a decline in the fertility of agricultural land, and this diminishes the competitiveness of Estonian agriculture. Analysed spatial DSS serves as a basis for effective resource management in modern agriculture and can be used as a tool in knowledge-based decision making processes to achieve economic, social and environmental targets of sustainable agriculture. The improvement of the current DSS and usage expansion from pilot areas to nationwide coverage of Estonia are essential for these purposes. This study creates possibilities not only for field-specific agro-economic analysis but also contributes a framework for further expansion of the capabilities of GIS-based DSS in various branches of the rural economy.