A pot experiment was conducted under greenhouse conditions using pots (perforated at the bottom), with 12 kg soil capacity of each. Pots were seeded with wheat (Triticum aestivum c.v. Sakha 8), to study the effects of traditional soluble-N and slow release-N fertilizers. The soil of each pot was thoroughly mixed with P at a rate of 12 mg P/kg soil. Soil K was in sufficient amount. The experimental pots were contained 288 pots, which arranged in a complete randomized block design with three replicate in four factors of three forms of soil , four N-fertilizers ( two traditional soluble-N and the other two slow release-N fertilizers) , three rates of N-fertilizers as well as two rates of moisture regimes of 70 and 100 WHC . At wheat maturity after 24 weeks-growth, plants in each pot were cut 2-cm above soil surface, carefully washed, dried and weighted. After wheat harvested and in the same pots, in order to study the Nfertilizes residual effect, two successive crops of Sorghum vulgar "c.v. Giza 15" and then barley "Hordium, vulgar c.v. Giza 121" were planted and harvested after 9 and 16 weeks , respectively. The obtained results may be summarized as follows:• The traditional soluble forms of N-fertilizers produced higher dry matter (gm./pot) of wheat crop compared with the slow release forms of N-fertilizers. • Dry weights (gm/pot) of both sorghum and barley were more under fertilization with slow release forms of N-fertilizers, than under fertilization with the traditional soluble forms, with approximately equal to two fold and threefold, respectively. • Slow release forms resulted in less N-uptake by wheat than the traditional soluble forms.While the slow release forms of N-fertilizers affected positively on N-uptake by both of sorghum and barley, with increases approximately equal to twice threefold more than the traditional soluble ones.• Residues of slow release N-fertilizers have appropriate supply of sorghum and barley, at the two successive with amounts of (N), because their ability to continuous supply (N) for long periods of time.

A heat flux plate was installed at 0.05m depth and thermo wires were installed at 0.05 and 0.3m depths in sandy soil with grasses of the surface at Ismailia Agriculture Research Station. Data of soil heat flux (G) (W/m 2 ) and soil temperatures were recorded every fifteen mints to represent 96 readings/day and air temperatures ( o C) were recorded every one hour. Finally, twenty four values for soil heat flux, soil temperatures were calculated and air temperature were recorded along a year. The objectives must study the soil heat flux at 0.05m depth and its relation to soil and air temperature. Also to calculate heat flux at 0.3m depth and determined the relation between G at 0.05m and G at 0.3m.The obtained results showed that soil heat flux values (W/m 2 ) at 0.05 m depth were higher at the day time with their peaks were at the mid day. The values became negative at night and early morning in the months of December, January, February and March, while the values became positive and low at early morning in the other months.Soil heat flux had been affected by both soil and air temperatures. The temperatures of air were more effective than soil temperatures of all months except for May and June. While, in March both temperatures had more or less similar effect on soil heat flux.The correlation coefficients and regression equations were significant between soil heat flux and either soil or air temperatures during the tested period.The values of calculated soil heat flux (G) at 0.30 m depth were less than those of measured soil heat flux (G) at 0.05 m, inspite of the significant values of correlation and regression between each other. Keyword: Soil heat flux (G) (Wm 2 ), soil temperature ( o C), Air temperature ( o C). INTRODUCTIONThe amount of thermal energy that moves through an area of soil in a unit of time is the soil heat flux or heat flux density. The ability of a soil to conduct heat determines how fast its temperature changes during a day or between seasons. Soil temperature is a key factor affecting the rate of chemical and biological processes in the El-Raies, S.A.A

The present study was conducted for three successive years in a sandy soil of Ismailia Agricultural Research Station (IARS). The abscissas of IARS are Latitude 30˚ 3 30 a d o gitude 3 ˚ 0 E and its elevation 10.2 meter over the sea level. Three thermal sensors were placed in the soil at depths of 0.05m, 0.10m, and 0.30m from the soil surface, to study the reflection effects of variations in the temperature of air on the variation of temperatures of the soil in the studied depths.The readings of air temperature (Air-T) were recorded with rate of one reading/hour, While soil temperature (Soil-T), at any soil depth was recorded with average of one reading/hour (i.e.24 readings/day). This means that, at any year, the recorded readings of (Air-T) or (soil-T) were 24 x365=8760 readings.The monthly averages of soil temperatures of the three depths throughout the three years were 13.

To study the variations of soil temperature in sandy soil and their relations to Alfalfa plant growth, eight thermal sensors were placed in two sites at different depths in a sandy soil at Ismailia Agricultural Research Station, and cultivated with alfalfa crop (Medicago sative) under sprinkler irrigation. After the plantation of alfalfa seeds, four plots were chosen for soil temperature (A, B, C, and D); each one represented one meter square plot. Two sites; one between A and B and the other between C and D plots were chosen to put the temperature sensors at four depths of; 0.05, 0.10, 0.15 and 0.30 m. At the end of the experiment, the average of the two sites was calculated for each depth. The alfalfa plants were cut every 28 days for each plot (seven days apart in dual way between the four plots) from January till October, where they equal 40 cuts/10 months. The results revealed that soil temperature decreased at the day night until the seventh to eightieth O'clock a.m., after sunrise it increased at the day light until the third to fifth O'clock p.m. at the surface layers depth for the previous months, while the values of the studied deepest layer (0.3m) decreased at day night until the ninth to tenth O'clock a.m., and after sunrise, it increased until the sixth to eighth O'clock p.m. after sunset. The minimum soil temperatures were 6, 6.64, 6.07 and 9.33ºC in February and the maximum were 35.58, 34.83, 38.15 and 31.79°C in July for the aforementioned depths, respectively. Alfalfa dry weight (kg/m 2 ) was positively significant correlated with the average soil temperature through the period of cuts. The minimum dry weight values (1.67 kg/m 2 ) was at the 2 nd cut at the temperature average (13.20°C), while the maximum values of dry weight (6.70 kg/m 2 ) was at the 23 rd cut at soil temperature average (26.20°C). The available K, Mn and Zn showed no significant correlation with soil temperature, while the available Fe was highly significant correlated with soil temperature. There were negative significant correlations between plant NPK concentrations and soil temperature, and this related to dilution with increase plant growth, whereas the uptake of P and K showed positive and significant correlation with soil temperature. Key words: alfalfa crop, sandy soil, soil temperature. INTRODUCTION:Soil temperature is a factor of primary importance in determining the rates and directions of soil physical properties and strongly influences its biological processes, such as seed germination, seedling emergence and growth, root development and microbial activity (Hillel, 2004). A change in soil temperature, caused by a gain or a loss of heat from the soil, depends on the specific heat and the

ABESTRACTFifty one registers (one every week) of soil temperatures in 51 weeks through twelve months from January to December were recorded for every depth. They were recorded for three soil depths (0.05, 0.15, and 0.30m) in sandy soil that covered with alfalfa plants in Ismailia Agriculture Research Station of Ismailia governorate. The total soil temperature registers recorded were (51 observations x 3 depths) 153 readings. One hundred and fifty three soil samples in the same 51 weeks were collected from the same locations of the three depths. The volumetric heat capacity, thermal conductivity and thermal diffusivity were calculated. The obtained results were summarized as follows:Soil volumetric heat capacity increased with increasing moisture content at the nearest soil surface depth (0.05m) or the deepest one (0.30m). They ranged from 1.345479 to 1.803934, 1.286049 to 1.678707 and from 1.281804 to 1.757947 MJm -3 c -1 for the three depths 0.05, 0.15 and 0.30m respectively.Soil thermal conductivity increased with increasing soil moisture content. The values ranged from 1.2603 to 2.2489, 1.23222 to 2.15026 and 1.03913 to 2.18332Jm -1 s -1 c -1 , at moisture content ranged from 0.024 to 0.133, 0.010 to 0.103 and 0.009 to 0.122m 3 m -3 for the abovementioned depths, respectively. However, soil temperature showed a small effect on increasing the thermal conductivity.Soil thermal diffusivity was affected by soil temperature and soil volumetric moisture content. They ranged from 9.