Modeling Soil Heat Flux in R

Knowing of soil heat flow properties of a crop field inform the farmer about temperature conditions of seeds germination. Soil heat flow today is either measured or modeled. In our study we rely on the procedure developed by Sang-Ok Chung and Robert Horton (1987). Applicability of the R language version heat flux model we studied on data collected by Gábor Szász director of the Agro-meteorological Observatory of Debrecen, Kismacs in May 2001.). Soil temperature data were collected in 5, 25 and 50 cm depth in 15 minute intervals from a loam texture chernozem soil covered with short grass. The used upper boundary layer at 5 cm and the lower boundary at 50 cm soil temperature data contain 2976 time periods. Temperature values measured at 5 and 50 cm depths were used as upper and lower boundary conditions, respectively. Using the R programmed heat flux model the 25 cm depth soil temperature was simulated and compared to the measured ones. Since the simulated and measured soil temperatures differed significantly we assumed necessity of coupling heat and moisture flux for describing time change of soil temperate. Our final conclusion is that because of the strong correlation between water flow and soil temperature, it is essential to make simultaneous estimations of them both when modeling soil temperature.</jats:p

A monokultúra és a vetésváltás hatásának vizsgálata a kukoricatermesztésben = Examining the effect of crop rotation and monoculture in maize production

A vetésváltásban termesztett kukorica egyértelműen, szignifikánsan több termést ad. Öntözött körülmények között a nem trágyázott parcellákon a vetésváltás termésnövelő hatása 55%-os. Trágyázás nélkül az elmúlt négy év (2003-2006) átlagában az öntözés csökkentette a kukorica termését! Amennyiben az öntözést műtrágyázással kombináljuk a vetésváltás termésnövelő hatása mérséklődik, értéke 8-10% körül alakul. Kedvező víz- és tápanyag-ellátottság esetén némelyik évben teljesen el is tűnik a vetésváltás kedvező hatása. A vetésváltásban kevesebb a talaj könnyen oldható nitrát tartalma, mint a monokultúrában. A trágyázás egyértelműen növeli a talaj nitrát és nitrit tartalmát. Vetésváltásban a nem trágyázott parcellákon alacsony, 5-7 ppm, a 120 N kg/ha parcellákon közel háromszor ennyi, 17-21 ppm a nitrát és nitrit tartalom. Öntözött körülmények között a vetésváltás nem befolyásolja a talaj nitrát-nitrit tartalmát, mert az öntözés nitrogén kilúgzó hatása mindkét kezelésben erősen jelentkezik. Az elvégzett vizsgálatok alapján az öntözött ill. öntözés nélküli körülmények között a talaj humusztartalmát sem a vetésváltás, sem a trágyázás nem befolyásolta szignifikánsan. A vetésváltás termésnövelő hatása egyértelműen a forgatást alkalmazó talajművelés esetén nagyobb. Ebben az esetben megközelíti a 30%-ot. Forgatásnélküli talajművelés esetében ez a hatás 13%-ra mérséklődik. Ezt érdemes figyelembe venni napjaink modern talajművelési rendszereiben, ahol sok esetben a forgatás mellőzik. | The maize produced in a rotation cycle gives expressly and significantly more yield. Under irrigated conditions the yield-increasing impact of the rotation cycle is of 55% on non-fertilised parcels. Under non-fertilised conditions the yield of maize was decreased by irrigation in the average of the last four years. In case we combine irrigation with fertilisation, the yield-increasing impact of rotation cycle is moderating, its value is about 8-10%. Under favourable water- and nutritive supply conditions, the favourable impact of rotation cycle completely disappears in certain years. The soluble nitrate content of the soil is less in rotation cycle than that in monoculture. Fertilisation increases the nitrate and nitrite content of the soil expressly. The nitrate-nitrite content in rotation cycle on non-fertilised parcels is low, about 5-7 ppm, while on parcels fertilised with 120 N kg/ha it is almost three times as much, that is 17-21 ppm. Under irrigated conditions rotation cycle does not affect the nitrate-nitrite content of the soil. The N leaching impact of irrigation is strongly present in both treatments. The yield-increasing impact of the rotation cycle is clearly stronger when the soil is tilled-up. In this case it is almost 30%, while in case of conservation tillage the impact reduces to 13%. This is worth considering in nowadays modern cultivation systems, where tillage is neglected in many cases

Investigating the long memory property of the Hungarian market pig prices by using detrended fluctuation analysis

Within the scope of this study we test the Long Memory property on monthly average pig market prices including piglet, young pig, sow and slaughter pig. We also calculate the Hurst exponent using Detrended Fluctuation Analysis (DFA) method. DFA is a method for determining the statistical self-affinity of a time serie. It is a useful technique for investigating time series with long memory (diverging correlation time and power-low decaying autocorrelation function. The obtained exponent by DFA is similar to those Hurst exponents estimated by other methods such as Rescaled Range (R/S) and AutoRegressive Fractionally Integrated Moving Average (ARFIMA), except the fact that DFA may also be applied to non-stacionary time series (mean and variance is changing with time) as in our case. We study the long memory property of the market pig prices. Data consist of four time series (piglet, young pig, sow, slaughter pig) between 1991 and 2013. Before the econometric analysis all the series were seasonally adjusted by using TRAMO/SEATS method. Data preparation was followed by differencing the time series and testing the normality and stationarity of them. In the next step we divided the analysed period to four parts and determined the Hurst exponent for each sub-period with the DFA method. So as to sum it up, slaughter pig prices are random, young pig and piglet prices developed similarly and have long memory, while sow price changes have definitely short memory</jats:p