Organic Carbon Changes Over 40-years in a Haplic Luvisol Type Farmland in Hungary

It is well known the effect of fertilizer applications in Haplic Luvisols after crop production, but long term changes in precipitation and soil organic carbon are not well documented. Study aimed to determine the effect of precipitation and fertilization (NPKCaMg) on the changes in soil organic carbon (SOC) in a long-term field experiment set up in Nyirlugos (Nyirseg region, Hungary: N: 47°41′60′′ and E: 22°2′80′′ since 1962) on a Haplic Luvisol. Over the 40 year period, from 1962 to 2002, SOC pool values ranged between 2.32 and 3.36 mg kg. On the untreated control plots the values remained nearly constant (3.31 mg kg, ± 0.29 mg kg and 0.52 mg kg). NPKCaMg fertilization resulted in a significant (P < 0.001) decline (16.6%) in SOC in comparison to the control plots in the 1 20-year interval, while in the 2 20-year period a significant (P < 0.001) increased (up to 31.9%) was noticed. During the 40 experimental years the seasonal correlations (R2) among SOC (mg kg), WHY and SHY precipitation (mm) ranged from 0.3343 to 0.9078 (on the P < 0.001 significance level). The correlations (R2) on the influence of NPKCaMg fertilization on SOC (mg kg) and precipitation (mm) were significant (P < 0.001): the means for WHY, SHY and over the 40 years were 0.4691, 0.6171 and 0.6582, respectively. Organic carbon reserves (mg kg) in soils decreased linearly as precipitation increased (from 3.22 to 7.27 mm yr). In case this trend-increasing precipitation caused by climate change reduces SOC in arable soils-will continue, and is aggravated by warming temperatures and a more altering climate (as predicted by climate change forecasts), the livelihoods of many Hungarian and European farmers may be substantially altered.