الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
SUMMARY
The present work aims at studying the main factors that limit the fertility in some sandy soils in Sinai and the possibility of using some natural (organic manure ”OM”) or and synthesized soil conditioners (some super absorbent materials ”hydrogels” having different ionicity ”G”) to modify the reverse effects of such limitations to reach proper providing of essential nutrients to growing plants. Obtained results could be summarized as follows :
I. Limitations of soil fertility in some sandy soils in Sinai :
Surface soil samples were collected from 17 locations to represent some new reclaimed areas, especially those have to be under agricultural development after entrance of El-Salam Canal water in Sinai. These include samples from east of Ismailia and El-Shabab farms to represent East Better Lakes Basin, from El-Quantara Shark to represent East Manzala Basin, from Rabaa and Bear El-Abd to represent South El-Bardawil Basin, from El-Taameer farms at El-Arish, Sheik Zoied, Rafah, OM Shihan and Nikhel to represent wadi El-Arish Basin and from Abou Sowaira, Sudr, Sahl El-Quaa valley Tur Sinai to represent East Gulf of Suez Basin. Particle size distribution, some hydrophysical and biological properties were determined to define limitations of soil fertility in the studied soils. Correlation coefficients relating soil properties by each other were calculated. Obtained data could be summarized as follows:
1-Particle size distribution of the studied soils indicate the dominancy of coarse texture (94% of the soils are sandy and only 6% are loamy sand) that refer to large size fractions, cohesionless nature, instability of the clods (single grain structure), rapid loss of water (rapid dry) and plant nutrients and highly exposed to both wind and water erosion.
2-Hydrophysical properties of the studied soils show their high percentages of macro-pores (drainable pores), low water holding capacity, filed capacity and available water range and high infiltration rate and hydraulic conductivity.
3-Biochemical properties of the studied soils refer to high pH, and low CEC, organic matter content, and available N, P and K. Salinity and
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high CaCO3 content may adversely affect soil properties in some locations. Low counts of micro-organisms (Bacteria, fungi and actinomycetes)/g soil and the low activity of both dehydrogenase and phosphatase indicate that these soils are biologically inert.
4- Statistical analysis of the data clarify that the main soil properties that limit fertility of the studied soils and needed to be modified are sand or clay%, available moisture, soil pH, OM content, CEC, plant nutrients, micro-organisms count and enzymes activity. Soil conditioning, proper fertilization and suitable irrigation management practices are needed to fulfill efficient utilization of nutrients and better cropping for such soils.
II. Effect of organic manure or/and acrvlamide hydrogels on Leachability and availability of N, P and K in sandy soils :
In a completely randomized columns experiment with three replications, Rafah sandy soil either untreated or treated with; a) organic manure (OM) at rates of 1, 2 and 4%, b) 0.2% of each of the acrylamide hydrogels, (G1) nonionic, (G2) anionic, (G3) cationic and (G4) mixture of G2 and G3 at the ratio of 2:3 (w/w), c) mixtures of OM and G at the rates of 1% OM + 0.1% G or 2% OM + 0.1% G or 2% OM + 0.2% G were examined. Two grams of a complex fertilizer 19:19:19 was added to each column through two methods of fertilizer application namely: (1) surface addition in one dose and leaching with distilled water (broadcasting treatment) or (2) dividing the fertilizer into ten doses and applying each dose dissolved in irrigation water as fertilizer solution having conc. of 1 g/L (fertigation treatment). Using a drip irrigation system, ten successive leachates were collected. Nitrogen (NH4+ and NO3”), P and K were estimated in each leachate. At the end of the tenth leachate, available forms of these elements in the soil were determined. Obtained results could be summarized as follows :
1- In the untreated soil, although addition of fertilizer by fertigation method reduces the fertilizers losses by leaching if compared with the other traditional method of fertilizer application (broadcasting), loss of fertilizer is still high (about 80% and 50% of added N, and 50 and 25% of added P and 90 and 60% of added K using both fertilizer application methods, respectively).
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2- a) Treating sandy soil with OM reduced N losses especially under fertigation treatment. More reduction was obtained by increasing the application rate of OM up 4%. Also leached NH4+-N was reduced from 36% in the untreated soil to be 19% at treated with 4% OM. Relevant values for NO3--N were 60.0 and 30.0%, respectively.
b) On the contrary, leached P and K from sandy soil treated with OM was increased by increasing the application rate of the conditioners, probably due to the effect of OM on transforming these elements to more soluble forms on one side and the high content of K in applied
OM on the other side.
3. a) Treating sandy soil with acrylamide hydrogels at the rate of 0.2% reduced leached nutrients especially under fertigation treatment to be 20-30% of added NH4+-N, 14-23% of added NO3--N, 18-24% of added P and 45-50% of added K. Chemical formulation of used hydrogel, i.e. its ionicity greatly affects the amounts of leached N in both cationic (NF14+-N) and anionic (NO3--N) forms.
Reduction leached N could be arranged descendingly due to G additions for NH4+-N as follows :
G2 > GI > G4 > G3
and for NO3”-N as follows :
G3 > G4 > G2 > G1
b) Similar trend was detected for P and K, the effect of studied hydrogels on reducing losses of P or K by leaching were desendingly
arranged as follows :
G1 = G3 > G4 > G2 for P
and G2 > G4 > G1 > G2 for K
4-Mixing OM with G increases the efficiency of added conditioners on reducing leached nutrients being higher with increasing the application rate of mixture’s components.
Obtained results clarify the efficiency of anionic G (G2) on reducing NIV-N and K losses and the cationic one (G3) on reducing leaching of
both NO3”-N and P.
5-a) Conditioning sandy soil increases retained nutrients in available forms in the soil after leaching especially when using the fertigation method. b) Addition of OM at the rate of 4% nearly doubled available of N and K in the soil after leaching and raised available P to be about 3 folds that of untreated soil. c) Increases in retained nutrients in sandy soil treated with 0.2% G ranged from 70 and 130% for N, 240 to 330%
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for P and 40 to 60% for K, according to the chemical formulation of applied G. The anionic hydrogel (G2) clearly increased available NI-14+-N and K while the cationic hydrogel (G3) in increased available NO3--N and P. d) Increases in retained nutrients in the soil in available forms by applying mixtures of OM and G differ due to the concentration of mixture’s components and the ionicity of added hydrogel being higher with increasing the application rate of either OM or G to plants in the mixture. Hydrogels in their mixtures with OM seem to have similar effect as if they were solely applied.
6- To get use of both anionic (G2) or cationic (G3) hydrogels, it seems preferable to apply their mixture, i.e. (G4).
III. Effect of organic manure or/and acrylamide hydrogels on growth response nutrients uptake and water and fertilizers use efficiency by Ryegrass plants in sandy soils :
In this part of research, a green house experiment within four replication conducted in a complete randomized system, using Ryegrass as an indicator plant.
Examined treatments were : a) untreated soil, b) soil treated with 2% or 4% OM, e) soil treated with 0.2% of the acrylamide hydrogel, GI, G2, G3 or G4, d) soil treated with mixtures of OM and hydrogels mentioned above at the rate of 1% OM + 0.1% G, 2% OM + 0.1% G and 2% OM + 0.2% G. Irrigation was adopted by fertigation system using 1 g/L fertilizer solution
19:19:19. Obtained results could be summarized as follows :
a- Examined conditioners significantly increased both forage yield and dry weight that reached 32.3% or 63.9% for forage yield and 18.4 or 41.7% for dry weight over that of the untreated sandy soil using 4% OM or 0.2% G respectively. Mixing both types of soil conditioners together increased both parameters. These increases by 72% or 76% for forage yield or dry weight under the treatment. 1% OM + 0.1% G. Relevant values for the treatment 2% OM + 0.1% G were 112 and 78%, respectively. Increasing hydrogel concentration through applying 2% OM + 0.2% G, slightly decreased both forage yield and dry weight by 10 to 15%, but in all cases the production was still higher than that of the untreated soil. b) Conditioning sandy soil increased N, P and K uptake of plants. For N, these increase reached 42.0%, 68%, 113% and
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122% using 4% OM, 0.2% G, 1% OM + 0.1% G, and 2% OM + 0.2% G. By doubling the rate of hydrogel compounds in mixtures to be 0.2% nitrogen uptake was slightly reduced (<10%). Increases in P and K nutrients uptake reached 57%, 87%, 133%, 141% and 124% for P and 61%, 83%, 129% 141% and 100 for K due to the treatments mentioned above in sequence. c) Soil conditioning increased water use efficiency by growing plants to reach 136% that of untreated soil with 4% OM, 172% with 0.2% G and 204%, 217% and 188% with the three mixtures of OM+G mentioned above, respectively. d) Soil conditioning increased the values of fertilizers use efficiency by plants to reach 1.4, 1.7, 1.8, 2.2 and 1.9 times that of untreated soil when treated with 4% OM, 0.2% G and the mixtures, 1% OM + 0.1 G, 2% OM + 0.1% G and 2% OM + 0.2% G, respectively. h) The results clarify the effect of anionic and cationic mixtures either solely added to soil or when mixed with OM. g) The reduction in growth, nutrients uptake or water and fertilizer use efficiency due to the treatment 2% OM + 0.2 G was explained on the basis of their effect on pore size distribution in soil towards the micropores and so its effect on increasing retained moisture in the soil to be over needs of growing plants, so it is recommended the use of lower rates of hydrogels or increasing the frequency of irrigation, i.e. reducing number of irrigation/season.
IV- Effect of organic manure or/and acrylamide hydrogels on some physicco-bio-chemical properties of sandy soils :
In order to evaluate the conditioning effect of both OM or G as well as their mixtures on soil properties, some hydrophysical, chemical and biological properties of the were determined at the end of green house experiment mentioned in Part III, i.e. after 150 days of plantation. Obtained results could be summarized as follows :
1. Hydrophysical properties :
a- Soil structure of treated sandy soil by both OM or G in more stable than that of untreated one. Water stable structural units > 0.25 mm in diameter reached 25% as 42 to 48% using 4% OM or 0.2% G in sequence compared with 20% for the untreated soil. Accordingly, structure coefficient was increased from 0.25 in untreated soil to be 0.34 or 0.73 to 0.94 with 4% OM or 0.2% G. Moreover, dry stable structural units > 0.84 mm in diameter, were increased from 10% in untreated soil to be 13% or 32-36% in treated one with 4% OM or 0.2% G. Therefore, wind erosion
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parameter was reduced from 1.0 in untreated soil to be 0.45 or 0.30-0.33 treated soil with 4% OM or 0.2% G. Mixtures of OM + G were more efficient than that of the individual conditioners. The rate of applying OM or G and the ionicity of G were the most important factors that affect structure stability. Stabilization was increased with increasing the application rate of each of both conditioners. Moreover, efficiency of using mixtures of OM and mixture of cationic and anionic hydrogel, i.e. G4 was
practical proved.
b-where as applied conditioners - either alone or in combination -decreased soil bulk density as well as the macro porosity (drinable pores > 28.8 M in diameter), they increased total porosity and micro pores relative to the macro ones indicating an improvement in the pore size distribution in sandy soil towards higher moisture retention and lower losses of water from the soil by leaching or deep percolation. While micro:macro porosity in untreated soil was only 0.33, such ratio increased to be 0.54 or 0.88-1.02 by treating the soil with 4% OM or 0.2% G. Data also indicate the importance of using mixtures of OM and G for improving pore size distribution in the soil where micro:macro reached 0.53, 0.65 and 1.2 using 1% OM + 0.1% G, 2% OM + 0.1 G and 2% OM + 0.2% G, respectively.
c-Retained moisture in sandy soil at all tensions under study (from 0 to 15 bars) were increased by soil conditioning. Because the increase in water retained in the soil at field capacity FC (pF=2.0) is far beyond that at wilting percentage WP (pF=4.2), the available water (FC-WP) in treated soil increased to be 1.56, 2.4-2.5, -:._ 1.6, :: 1.9 and __-_ 2.9 times that of untreated soil by incorporating 4% OM, 0.25 G, 1% OM + 0.1% G, 27.0 OM + 0.1% G and 2% OM + 0.2% G in the soil, respectively.
d-Incorporating either OM or/and hydrogels in sandy soil decreases its mean pore diameter 0 and in turn water transmitting properties namely : infiltration rate (IR), hydraulic conductivity, (K) and transmissivity for vertical flow of water through the soil profile (E K/D) to reach 33.9 or 47.1% for e, 33.1 or 47.6% for IR, 15.0 or 28.1% for K and 24.8 or 36.1% for E K/D by treating the soil with 4% OM or 0.2% G, respectively that of
untreated soil.
Treating the soil with mixtures of OM and G was more efficient than using each of them alone. Reduction in the values of water transmitting properties under study relative to that of untreated soil reached 40.9%, 44.5% and 51.3% for IR, 375, 41.4 and 52.1% for K, 20.9%, 23.5% and 31.0% to 0 and 28.1, 31.1 and 39.1 for EKJD with 1% OM, 0.1% G, 21.0 OM + 0.1% G and 2% OM + 0.2% G, respectively.
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h- Loss of water from sandy soil through evaporation was reduced by soil conditioning. Conditioning treatments could be arranged according to their effect or reducing evaporation as follows:
0.2% G > H% OM > untreated soil with an adjusted evaporation (E adj.) of 0.817; 0.569 and 1.0 for
E treated soil
E adj. = - - - - - - - - - - - - - x
WHC treated soil
WHC untreated soil
E untreated soil
Incorporating OM in the soil mixed with G was more effective than using each of them alone, where E adj. have reached 0.665, 0.630 and 0.480 for the treatments 1% OM + 0.1% G, 2% OM + 0.1% G and 2% OM + 0.2% G, respectively.
2. Chemical and biological characteristics :
a-using OM or G or mixtures of both as soil conditioners reduced its pH. This reduction was 0.06 or 0.1 unit with 2% or 4% OM and ranged between 0.23 and 0.4 units, 0.17 and 0.23 units and 0.1 and 0.18 units with 1% OM + 0.1% G, 2% OM + 0.1% and 2% OM + 0.2% G, respectively.
b-Conditioning increases CEC and surface area of the soil, the refers to beneficial effects on the chemical activity of treated soil. With this respect, applying 4% OM or 2.2% G compounds or mixture of 1% OM + 0.1% G nearly doubled CEC and surface area of the soil. By increasing the application rate of each of OM or G in the mixture of conditioners, the two factors under study were increased to be to two and half and three folds than that of untreated soil, by applying 2% OM + 0.1% G and 2% OM + 0.2% G, respectively.
c-Soil conditioning increased OM %. Accordingly, OC content was increased to reach 7.7 or 4.7 times that of untreated soil using 4% OM or 0.2% G. Organic matter % or organic C content ranged between 4.1 and 4.6 times, 5.3 and 6.4 times and 6.5 and 7.6 times than of untreated soil using mixtures of 1% OM + 0.1% G, 2% OM + 0.1% G and 2% OM + 0.2% G, respectively.
d-Similarly, total N and organic N take the same trend of OM% and organic carbon content. Compared with these of untreated soil Total N increased to reach 14.2 times with 4% OM and 7.2-8.4 times with 0.2% G. With this respect, organic N reached 38 times and 17.6-21.2 times that of untreated sandy soil using the two conditioners mentioned above, respectively. Increases in total N, using mixtures of OM and G ranged
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between 6.8 and 7.2 times, 8.2 and 10.1 times and 10.4 and 11.6 times and in organic N between 16.7 and 17.2 times, 20.9 and 26.4 times and 26.3 and 30.4 times that of untreated soil using their mixtures of conditioners mentioned above, respectively. Because the increase in total N is higher than that in organic C, CN ratio be more narrower than that of untreated sandy soil to be 6.44:1, 6.61:1 to 7.32:1, or 6.7:1 to 7.2:1, 7.57:1-7.86:1 and 7.14:1 to 7.84:1 by applying 4% OM, 0.2% G, 1% OM + 0.1% G, 2% OM + 0.1% G and 2% OM + 0.2% G, respectively. Such narrow CN ratio indicate the easy mineralization of organic nitrogen compounds, hence the possibility to save and provide available forms of N to growing plants.
e- Sandy soil conditioning significantly increase nutrients availability in the soil. Applying 4% OM or 0.2% G to sandy soil raised available N to be 2.1 or 2.0 times, available P to be 2.0 or 1.75 times and available K to be 3.2 or 2.35 times that of untreated soil. Relevant values for mixtures of 1% OM + 0.1% G, 2% OM + 0.1% G and 2% OM + 0.2% G were 1.74, 1.90 and 2.29 times for N and 1.65, 2.27 and 2.65 times for P and 2.53, 3.63 and 4.52 times for K, respectively.
Ionicity of studied hydrogels is considered of the most important factor that nutrients availability (in both anionic and cationic forms). Accordingly, the effect of examined hydrogels on increasing the availability of nutrients in its cationic forms, i.e. NI-14÷-N or le was descendingly arranged is follows :
Anionic G > mixture of anionic + cationic G > cationic forms, i.e. NO3”-N and H2 PO4 was arranged in the some manner as follows :
Cationic G > mixture of anionic + cationic G > anionic G > nonionic G.
I- Biological activities of sandy soil is measured by total number of microorganisms (bacteria, fungi and actenomysites)/g soil and the activities of both dehydrogenase and phosphatese enzymes were increased by soil conditioning. Such increases in total number of bacteria have reached 4.97%, 103%, 323%, 397% and 435% by treating the soil with 4% OM, 0.2% G, 1% OM + 0.1% G, 2% OM + 0.1% G and 2% OM + 0.2% G, respectively.
Similarly, relevant increase in total number of fungi were 25967%, 12233%, 17433%, 14700% and 23467% and in total number of actinomycetes 475%, in sequence, addition of 4% OM raised the enzymes activities in treated soil to be ten folds for dehydrogenase and 3.5 folds that of untreated soil for phosphatase. As expected, increases in enzymes
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activity when applying hydrogels will be lower than that of OM. Increasing in enzymes activity relative to the untreated soil due to the addition of 0.2% hydrogels have reached 2.6 and 2.0 times for both enzymes, in sequence, being higher with G4, i.e. anionic +cationc hydrogel compound with untreated soil, enzymes activity have reached 7.2, 8.4 and 9.4 times for dehydrogenase 2.8, 3.3 and 37 times for phosphatase by treating the soil with 1% OM + 0.1% G, 2% OM + 0.1% g and 2% OM + 0.2% G, respectively.
Obtained results could be discussed on the basis of combined and interacted effects of both OM and hydrogels on hydrophysical, chemical and biological properties of sandy soil and in turn on plant growth nutrient uptake and both water and fertilizers use efficiency by growing plant where a conclusion was drawn that mixing both types of soil conditioners together was more efficient on improving soil properties that applying each of them alone. Application rate of mixture’s components and the ionicity of applied hydrogels are considered of important factors that highly affect soil conditioning.
Results clarify the high efficiency of using mixtures of anionic and cationic hydrogels (2:3) particularly when combined with OM.
When evaluating the use of such technique for sandy soil conditioning one has to take in consideration the improvement in hydrophysical, chemical, biological properties and nutritional status of the soil an in turn the increase in its productivity and the lowing the prices of irrigation water and fertilizer on one side and the prices of the conditioners used and costs at the condition process on the other side. With this respect, applying 2% OM mixed with 0.1% of a mixture of anionic and cationic hydrogels at the rate of 2:3 to sandy soil could be recommended to reach high efficiency of soil conditioning without reverse effects on plant growth, nutrients uptake and both water and fertilizer use efficiency by growing plants.