AGRONOMIJAS VĒSTIS - Latvijas Lauksaimniecības universitāte

AGRONOMIJAS VĒSTIS (Latvian Journal of Agronomy), No.10, LLU, 2008Table 2. Effect of soil amendments and primary tillage on the crop yield, Mg ha -1YearTreatment2001 2002 2003winterspringpeaswheatbarleyAmendments (Factor A)Without amendments 5.11 3.63 3.21Farmyard manure 5.58 4.09 3.58Green manure 5.42 3.89 3.49Lime – mud 5.34 3.92 3.51LSD 05 A 0.063 0.082 0.132Incorporation methods of amendments (Factor B)With a moldboard plough at 0.25 m depth 5.30 3.89 3.59With a segment plough at 0.40 m depth 5.42 3.88 3.31LSD 05 B 0.036 0.047 0.076Soil tillage after incorporation of amendments (Factor C)Ploughing at 0.25 m depth 5.42 4.30 4.27Ploughless loosening at 0.25 m depth 5.36 3.72 3.12Ploughless loosening at 0.15 m depth 5.32 3.63 2.96LSD 05 C 0.051 0.067 0.108DiscussionsPhysical soil protection requires the avoidance of soil compaction. Therefore, clayey soils,noted for higher susceptibility to physical degradation, must be improved and the soil propertiesmust meet the requirements of sustainable tillage technologies (Maiksteniene, 1997; Balesdent etal., 2000; Palojarvi and Nuutinen, 2002). Our experiments showed that soil amendments of organicand inorganic origin had a greater effect on the improvement of the soil physical properties (bulkdensity, total and air-filled porosity, structure) in topsoil, than in subsoil. The positive effect offarmyard manure and lime mud lasted mostly three years and the effect of green manure one or twoyear after application. Only lime mud was effective for subsoil improvement.The influence of the incorporation of amendments with a segment plough on the waterconductivity in the subsoil increased even more in the third year of influence. The worsening of thesoil structure and water conductivity in the topsoil after segment ploughing was determined bymixing poorer quality clayey subsoil with more structured and more water conductive topsoil. Thefindings of other authors result in similar conclusion (Hakansson and Petelkau, 1994).In clayey soils it is very important to secure a good germination of spring crops, whichconditions their further growth, because having dry conditions in the topsoil the available watercontent for plants is limited; close to the plant wilting moisture content. The transition fromconventional to reduced tillage usually leads to the decrease in the yield of spring sown cereals.According to Finnish scientists, the main reason for this agronomic problem is coarse seedbeds,and therefore poorer germination of cereal seed, because of worse contact with the coarse soilaggregates and smaller reserves of the moisture in it (Pietola and Tanni, 2003). The application ofreduced ploughless tillage to spring crops in our study resulted in the deterioration of seedbedquality, reduction of soil porosity and, revealed later, however, a more uniform drying of thetopsoil before pre-sowing tillage in spring resulting from a better capillary regime compared withploughing.Our findings also show that spring sown cereals were susceptible to the reduction ofprimary clay loam soil tillage. Feiza and Cesevicius (2006) found, that reduced tillage can result inthe reduction of cereal yield even on sandy loam soils under Lithuania’s conditions. Theincorporation of amendments in our experiment, especially farmyard manure in separate caseshelped to avoid the crop yield reduction caused by the application of reduced soil tillage.Therefore, efforts focused in improving clayey soil properties are of great importance during thetransition to reduced tillage.76