IMPACT OF MOLE DRAINS AND N-FERTILIZER RATES ON SOME SOIL PROPERTIES AND SUGAR BEET PRODUCTION IN CLAY SOIL

El-Henawy A. S. A field experiment was conducted during two winter seasons 2013/2014 and 2014/2015 at El-HamulDistrict, Kafr El-Shiek Governorate, Egypt, to study and evaluate the effect of mole drains (2 and 4 m spacing between the ploughed lines and 60 cm depth) and applied N-fertilizer rates (100 N, 115 N and 130 N % from the recommended) + 3 ton/fed. of gypsum before cultivation on improving some soil physio-chemical properties and sugar beet production in heavy clay salt affected soil.


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The lowest values of N-uptake (35.20 to 36.44 kg.fed -1 ) were found with control, and the highest ones (44.10 to 55.38 kgfed -1 ) were found with treatments in both seasons.The low values of impurities (K, Na andAlfa-amino -N) in sugar beet roots were found with treatments compared to the control.

Introduction:-
Soil salinity and sodicity are one of the main agricultural problems limiting plant, growth and development in the world especially in arid and semiarid regions (Pessarakli, 2010). In Egypt, northern part of the Nile Delta represents a large area of heavy clay soils with shallow drainage which are low permeability that might have a low productivity.
Drainage plays a vital role in low permeable clay soils in order to prevent soil degradation. A secondary drainage treatment of moling seeks to be an inexpensive "drain" at close spacing, intercepted by permanent laterals at wider spacing. Moling is the best suited to clay soils with a minimum clay content of about 30%. Mole drainage, on the suitable soil type and done properly can reduce waterlogging problems. Mole drainage is widely used on heavy soils to improve productivity of pastures and crops (David, 2002). Improved salt affected soils and crop growth following subsurface drainage and mole drains are generally considered to be the result of the physical shattering of the hardpan, which allows to increase water penetration into the subsoil. This may also accelerate the leaching of sodium from the subsoil thereby further reducing the possibility of reformation of the hardpan (Lickacz, 1993).Antar, et al., (2008 and 2014) and Aiad et al., 2012found that subsurface tillage seemed to be effective in lowering soil salinity and sodicity and bulk density especially in the soil depth (0-60cm). Sugar beet yields are related to the salinity contents in soil.The yields increased when the EC decreased as affected by subsoiling and/or moling.
Alkali soils which are characterized by their adverse physical properties, their dispersed condition and impermeability to water, are to be directly connected with sodium as the dominant exchangeable base and the presence of magnesium silicate precipitated during the process of soil alkalinization. Gypsum applications followed by leaching, and biological methods such as growing salt-tolerant crops, were found successful in reclamation of a number of sodic and saline-sodic soils having good drainage conditions Sugar beet (Beta vulgaris L) is the second important crop for sugar production in Egypt. The importance of this crop comes not only for its ability for growing in the new reclaimed lands, but also for giving higher sugar content and short growth period. Also, sugar beet is widely grown in areas with salinity problems. So, there is a great need for several studies under Egyptian soil conditions to establish the best recommendations for raising the quantity and quality of sugar beet production. One way of increasing production of sugar beet is proper soil management such as drainage and increasing the efficiency of added nitrogen fertilizer. Sugar beetyield is affected by many factors such as drainage conditions and nitrogen fertilizer. The current study aims to study and evaluate the effect of mole drainsand applied N-fertilizer rates on improving some soil physio-chemical properties and sugar beet production in heavy clay soil.

Materials and methods:-
A field experiment was conducted through two winter seasons 2013/2014 and 2014/2015 at El-HamulDistrict, Kafr El-Shiek Governorate, Egypt), to evaluate the effect of mole drains (2 and 4 m spacing between the ploughed lines and 60 cm depth) and applied N-fertilizer rates (100 N, 115 N and 130 N % from the recommended dose) on improving some soil physio-chemical properties and sugar beet production in heavy clay salt affected soil. The location is situated at 31° 18′ 12″ 7 N latitude and 31° 03′ 30″ 5 E longitude. Nitrogen fertilizer in the form of urea was added in three doses (before the first, second and the third irrigations). All plots received 3 ton/fed. of gypsum before cultivation as recommended. The different agricultural practices were done as recommended through the two growing seasons. The salinity of irrigation water ranges between 0.8 -0.6 dSm-1 with an average of 0.70 dSm -1 . The initial of some soil properties for the experimental field are presented in Table (1). The experiment design was a randomized complete block in seven treatments with three replicates as follows: 1. Open drainage + 100% of the recommended N (90Kg N/fed) (control). 2. Mole drains at 2m spacing + 100% of the recommended N (90Kg N/fed). 3. Mole drains at 2m spacing + 115% of the recommended N (104Kg N/fed). 4. Mole drains at 2m spacing +130% of the recommended N (117Kg N/fed). 5. Mole drains at 4m spacing + 100% of the recommended N (90Kg N/fed). 6. Mole drains at 4m spacing +115% of the recommended N (104Kg N/fed). 7. Mole drains at 4m spacing + 130% of the recommended N (117Kg N/fed).
Before winter season 2013/2014, mole drains installation with twodistances between the ploughed lines (2and 4m) and 60 cm depth perpendicular to the open drainage. "Mole drains are unlined channels formed in a clay subsoil with a ripper blade with a cylindrical foot, often with an expander which helps compact the channel wall." Open drain was used to collect the drainage water brought by mole drain channels.
In the two growing seasons, seeds of sugar beet (pleno cultivar) were sown. The plants were thinned to one plant before the first irrigation. All plots received 100 KgCa-superphosphate/fed, and 50 Kg K-sulfate/fed, during tillage operation. Soil samples (0-15, 15-30, 30-60 and 60-90cm depth) were collected before experiment and after the first and second seasons from treatments instillation for all treatments and monitored for some physical and chemical analysis. Salinity was determined in saturated soil best extract according to Page et al. (1982). Exchangeable sodium was determined using ammonium chloride and measured by using flame photometer according to Page et al. (1982). Soil bulk density and total porosity of the different layers of soil profile were measured before experiment and after the first and second seasons from treatments instillation for all treatments using the core sampling technique as described by Campbell (1994). Soil penetration resistance (SPR) was determined by hand penetrometer apparatus (Read by Newton/cm2) and, convert the Newton into Mega Pascal (MPa) values (100 Newton/cm 2 = 1 Mega Pascal). Infiltration rate was determined using double cylinder infiltrometer as described by Garcia (1978). At harvest, root and top yields and sugar yield as ton/fed were determined in both seasons.
Sucrose % and juice purity % were determined in Delta company sugar in El-Hamul district. Sugar yield was Calculated from multiplied root yield (ton / fed) x sucrose % Alkaline coefficient (Ac) calculated as follow: Ac= [(Na+K) ⁄ ( α-amino N)] according to Wieninger and kubadinow 1971 and polloch 1984 . Statistical analysis: Some of the obtained data are subjected to statistical analysis according to Snedecor and Cochran (1980). Treatments were compared by Duncan's multiple range test (Duncan, 1955)  Results and discussion:-Soil salinity and sodcity:-Data presented in Tables (1 and 2) show that, application of mole drainsseem to be more effective in decreasing soil salinity and sodcity in presence gypsum. The salinity and sodcity of the soil increased markedly with the increasing of soil depth. Soil salinity and sodcityin the topsoil up to 60cm, before treatments application (Table, 1) are relatively high (EC e varied from 7.98 to 10.54 dSm -1 and ESP from 16.74 to 19.16) comparing with that after the first and second seasons (Table, 2) which, varied from 5.13 to 9.24 dSm -1 for EC e and 13.05 to 17.56 for ESP. The decreases of soil salinity and sodcity in the topsoil up to 60cm, after the second season of treatment installation are more pronounced compared to that after one season (Table, 2). Salinity and sodcityof the soil are decreased in the upper layer (0-60cm) in all treatments while, no decrease was shown in the deeper layer 60-90cm. These results might be explained by the effect of mole drains on water table recession, which occurred only through mole depth and thus contributed to an active salt transfer during the falling of water   Table (3) show that, application of mole drains and added of gypsum seemed to be more effective on increasing Ca ++ /TSS ratio in the topsoil up to 60cm, than before application and control treatment. The increases of Ca ++ /TSS ratio after the second season are more pronounced compared to that after the first season. This may be due to the leachability of Na + is higher than that of Ca ++ and Mg ++ with mole drains. Also, Na + and Cl − are leached more readily than SO 4 + , Ca ++ and Mg ++ . In this concern, Ali and Kahlown (2001) mentioned that reclamation of salinesodic and sodic soils, however, can not be achieved by simple leaching. Reclamation of these soils is difficult, time consuming and more expensive than that of saline soils due to replacement of exchangeable sodium with calcium. Hence, it requires the addition of chemical amendments such as gypsum along with leaching. Change in Ca ++ /TSS ratio were no observed in deeper layer (60-90cm). Whereas, mole drains is effective in removing salts especially Na + from the topsoil up to 60cm. Results also, show that, narrow mole spacing (2m) is superior to wider mole spacing (4m) in increasing Ca ++ /TSS ratio. This may be due to the good effectiveness of narrow mole spacing (2m) than wider mole spacing (4m). While, no obvious different betweenCa ++ /TSS ratio values under N-fertilizerrates treatments in both seasons.    (6) showed clearly that the N-uptake (kg/fed.) by roots and tops of sugar beetwere parallel to the yield results in both seasons. Whereas, mole drains application and increasing N-fertilizer rate (from 100 to 115 and 130% from the recommended N) caused increases for N-uptake by sugar beet roots and topscompared to control. The low values of N-uptake (35.20 and 36.44 kgfed -1 ) were found with control treatment, while the high ones (44.10 and 55.38 kgfed -1 ) were found after treatments application in both seasons, respectively.The high values of impurities (K and Na) in sugar beet roots were found with control treatment, while the low ones were found after treatments application in both seasons. On the other side α-amino-N take opposite trend than K and Na in both seasons and gave lowest values with control. Potassium , sodium and alfaamino nitrogen (K , Na and α -N) were determined as (g / 100 g sugar)Alkaline coefficient:-Regarding to alkaline coefficient as affected by mole drains and nitrogen levels, data presentedin Table (6) cleared that with increasing nitrogen levels up to 100% from recomendation dose to 130% caused to decreasing (AC) to(1.74 and 1.73) in both seasons, This mean that if (Ac) decrease than (1.8) this indicator that over fertilization happen. So, we must take care from increasing nitrogen dose which decreasing (Ac) low than (1.8).

Conclusion:-
 Molingis good way in clay soils to reserve the root zone from water logging and salinity in presence gypsum.  Mole draintend to improve soil physio-chemical characteristics and increase sugar beet production.