Assessment of soil and climate factors on chestnut productivity for Kastamonu region

Chestnut trees are mostly cultivated for their fruit and wood. About 111.044 hectares (0.5%) of Turkish land is covered by Chestnut forests. With regards to the fruit, it is used in preparations of many recipes due to its dietetic value. Due to its economic and nutritional value, the world production of chestnuts is increasing as new stands are being planted in various regions of the world. According to FAO statistics (FAO, 2012), Turkey was the third world's largest producer in 2011 with 59.789 tons (40.000 tons in the 60s); the world's largest producers are China (1.650.000 tons), Republic of Korea (70.000 tons), and Turkey (59.789 tons). In Europe and Turkey, the most important chestnut specie is Castanea sativa Mill., one of 13 species from Castanea genus. According to the chestnut distribution map, there are 23.341,7 ha chestnut stands at the border of Kastamonu Forest District Directorate. There are 11,1% pure and 80,4% chestnut mixture stands with other deciduous tree species. %83,5 (19498,2 ha) chestnut stands are on the shady aspect and 16,5% (3843,5 ha) on the sunny aspects. Chestnut stands in general (97,7%) grow at the altitude of 500 m-1500m. All species of plants are dependent on the weather and soil with regards to their production. We know from literature that chestnut species generally dislikes chalky soil, but appreciats sedimentary or siliceous soils. Their roots tend to decay in poorly drained soils. It can be found on acidic to neutral soils, and influenced by sea climate which is characterised by annual mean rainfall ranging between 600 and 1500 mm, mean annual temperature between 9 and 13 oC, 27 oC being the mean of the maximal temperature. Among soil properties, only soil pH and clay content showed significant differences between altitudes (P< 0.05 and P<0.001 respectively). There were also significant differences in soil porosity (P<0.01), soil pH (P<0.05) and bulk density (P<0.01) between the soil depths. Soil moisture, silt and sand contents did not vary between the altitudes or between the soil depths. Mean soil pH at the lower altitude (6.13) was higher than that at the higher altitude (5.55), whereas clay content at the lower altitude was lower (19%) than that at the higher altitude (28%). In general, soil porosity a showed an increase with soil depths, whereas soil pH and soil bulk density decreased with the soil depths. Only soil organic carbon content showed significant differences between the altitudes (P<0.05), while soil organic carbon (P<0.05), total nitrogen stock capacity (P<0.01) and soil organic carbon stock capacity (P<0.01) had a significant difference between the soil depths. Soil organic carbon decreased with increasing altitudes. At the lower altitude (41 m), mean soil organic carbon was 2.65%, while at the higher altitude (305 m) it was 1.91%). As for the SOC and STN stock capacities, there were indications that mean soil organic carbon and nitrogen stock capacities decreased with increasing altitudes, but this was not statistically significant. Soil macro nutrients (Mg, P and K) showed significant differences between the altitudes (P<0.001; P<0.01 and P<0.001 respectively), while all soil macro nutrients (Ca, Mg, P, K and S) had significant variations with the soil depths. Mean soil macro nutrients; Mg and K concentrations were significantly higher at the higher altitude than those at the lower altitude, whereas mean soil P concentration was lower at the higher altitude than those at the lower altitude. All soil micro nutrients (Fe, Mn, Na, Cu, Zn, Cl, Al and Co) showed significant variations either between the three altitudes or between the soil depths. Soil micro nutrients, Fe, Mn, Cu, Zn, and Co concentrations were significantly lower at the higher altitude than those at the lower altitude, while Na and Al concentrations were higher at the higher than at the lower altitude. As a result of the work done, results and suggestions were made to improve the chestnut forests, to benefit from the existing chestnut fields at the maximum level, to combat the diseases and harms. Keywords: Castanea sativa, soil properties, climate, production, Kastamonu