The use of synthetic soil conditioners such as polyvinyl alcohol (PVA), bitumen (Bit.) and polyacrylamide (PAC) can be considered as a specific management to improve the efficiency of the use of nitrogen fertilizers and some chemical properties of calcareous soils that are reflected in crop productivity. Two rates of synthetic soil conditioners (PAV, Bit. and PAC) and three rates of nitrogen fertilizer (50, 75 and 100% N of recommended dose) were included in this study to evaluate their effects on some chemical properties, nutritional status and yield components of both maize and wheat crops along with nitrogen use efficiency. Field experiments were conducted in calcareous soil at Nubaria Agriculture Research Station farm during two successive seasons, summer season cultivated with maize (Zea mays L., cv Giza 10) and winter season cultivated with wheat ( Triticum aestivum L., cv Giza 168). Results showed that the highest significant yield components of maize and wheat crops along with their total content of the indicated macronutrients were observed when applied high rate of polyvinyl alcohol (0.2 %) accompanied with high rate of nitrogen fertilizer (100% N of recommended dose) as compared to other tested treatments. On the contrary, application of high rate polyacrylamide combined with low rate of nitrogen fertilizer generally was inferior for yield components of both maize and wheat plants. Also, data revealed that the nitrogen use efficiency was the highest (65.0 and 42.4) for maize and wheat plant, respectively, receiving 50 % nitrogen fertilizer rate in presence of 0.2 % polyvinyl alcohol. However, applied high rate of polyvinyl alcohol accompanied with low rate of nitrogen fertilizer was superior decreased pH values of soil as compared to either control or other tested treatments. An opposite trend for EC values which were superior increased in presences of all nitrogen fertilizer rates. Also, CaCO 3 values were lower when applied high rate of polyacrylamide in two seasons. The highest values of available nitrate and ammonium in soil were due to applied 0.2 % of polyvinyl alcohol combined with 75 % of nitrogen fertilizer rate compared to the other tested treatments.
This study was carried out during the winter two seasons 2015 , 2016 on wheat (Triticum aestivum L.) at Malawi Agricultural Research Station in El-Minya Governorate, Egypt to study the effectiveness of three irrigation scheduling treatments (farmer practice (I1), irrigation with 100% ET o (I2) and irrigation with 75% of ET o (I3)) along with five treatments (100% N, potassium humate (KH), 75%N+KH, 50% N +KH and 25%N +KH). Results of soil chemical properties revealed that no great variables were observed in pH values between all treatments either when applied full dose of nitrogen fertilizer (100% N) , Khumate (KH) alone or Khumate (KH) in combination with nitrogen rates. This result was true for both studied season. Mean values of soil EC, in general, were increased when applied low nitrogen rate. Also, irrigation at I3 (75% ET 0) recorded high value of EC as compared to other irrigation treatments. Moreover, organic matter values were increased as affected by Khumate application as compared with control treatment (only nitrogen fertilizer) as well as OM content in I1 (Farmer practice) irrigation treatment decreased as compared to other application irrigation treatments. Concerning available N,P and K mean values showed an increase in N , P and K availability when applied Khumate in combination with nitrogen fertilizer as compared to applied N fertilizer alone. Applied Khumate with 75% N seems to be favorable treatment than other treatments. Applied Irrigation treatment 75% Et 0 was superior for NPK availability as compared to other irrigation treatment. Also, date reveled that highest crop water requirements (CWR) and seasonal water consumption use (WCU) under farmer irrigation practice in the two growing seasons and the lowest value was under irrigation treatment with (I3) of ET o. The mean values of WCU were decreased when applied different nitrogen rates The value of WUE as a mean of two growing seasons were higher with irrigation treatment (I2) , also, with K humate in combination with 75% N rate.In addition, data showed that wheat yield and its components had significantly influenced by different applied treatments, compared to the control treatment. The plants receiving irrigation treatment at (100% of ET o) in presence of KH +75% nitrogen gave the highest wheat yield components as compared to other tested treatments. Similar trend was recorded for total content of nitrogen, phosphors and potassium in wheat plant.
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.
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