EURASIAN JOURNAL OF SOIL SCIENCE

1-9

Authors: Abdelmonem Mohamed Ahmed Amer

Sorptivity (S) has been defined in terms of the horizontal infiltration equation. At unsaturated conditions (at a very short time) S represents “maximum sorption capacity”, but in saturated conditions the sorption capacity decreases with the time. Over a long time of infiltration, sorptivity was not studied as a soil water parameter that could be determined. The purpose of this study is to apply derived equations depending on the infiltration functions to predict (1) soil water sorptivity (S) at infiltration capacity (unsaturated conditions) and at basic infiltration rate (Ib) (saturated conditions), (2) the hydraulic conductivity (Saturated Ks and unsaturated K(θ)) into capillary-matrix and non-capillary macro pores of soils. Five alluvial (saline and non-saline clay) and calcareous soil profiles located in the Nile Delta were investigated for applying the assumed equations. A decrease in S value was observed with an increase in soil water content. At steady infiltration rate (Ib), S decreased from 1.04 to 0.647cm.min-0.5 (i.e. S decreased by 37.79%) in average in calcareous soils and from 0.537 to 0.251cm.min-0.5 (53.25%) in alluvial clay soils. The steady Sw parameter was used in prediction of the hydraulic conductivities and the basic infiltration rate Ib , whereas, Sw is a suggested term at steady infiltration rate. The calculated values of Ib were corresponding to those obtained by infiltration experiment. This confirmed the significance of steady Sw as a new functional infiltration parameter. A matching factor u was calculated as a ratio between predicted Ib and the measured saturated hydraulic conductivity, Ks. The mean values of u were 0.895, 0.685 and 0.360 for calcareous, clay and saline clay soils respectively. Unsaturated K(θ) has been discriminated into saturated macro-pore K(θ)RDP and matrix unsaturated K(θ)h. The values of K(θ)RDP for macro pores remained higher than those for soil matrix pores (K(θ)h) in the studied soils. The highest value of K(θ) was obvious in calcareous soil profiles, while the lowest value was existed in saline clay soil. In conclusion, the predicted values of hydraulic conductivities of soil matrix (capillary) and macro (non-capillary) pores were reasonable and existed in the normal ranges of the investigated soils, indicating that the proposed equations are applicable and can be recommended to be used in coarse and fine textured soils with large scale of different properties.

18-23

Authors: Luiz Felippe Salemi, Rafael Pires Fernandes , Robson Willians da Costa Silva , Lara Gabrielle Garcia , Jorge Marcos de Moraes , Juliano Daniel Groppo , Luiz Antonio Martinelli

There have been a number of studies dealing with soil hydraulic properties. Yet, there is a poor discussion on the number of samples necessary to represent such variables that usually vary orders of magnitude in space. In the present paper, we examine the adequate number of samples for two soil saturated hydraulic conductivity (Ksat) data sets: (1) normal distribution (a 40 year-old pasture) and (2) non-normal distribution (primary forest). To assess the adequate number of samples in each case, we used for normal distribution, an statistical criterion of standard deviation lower than 5% compared to a high sampling effort (n = 25) as an indicative of a proper representation of Ksat variability. In the case of non-normal distribution, we used the same criterion but using median absolute deviation (a non-parametric statistics). Both data sets were available in Salemi et al. (2013) and were Ksat measured at 0.15 m soil depth for medium-textured inceptisols in São Paulo State, Brazil. For each data set, we simulated 10 ‘new’ samplings in which we calculated mean and standard deviation from sample 1 to 25 (for normal data) and median and median absolute deviation (for non-normal data). We found that, on average, at least 17 to 22 samples had to be collected to meet the adopted criterion for normal data whereas 20 to 25 had to be collected for non-normal data. Such numbers of samples exceed those used in a number of papers. Additional examples of this method with a light modification are given to establish number of samples in new study areas as well as to estimate number of samples when comparing two (or more) land-uses. Simple and practical procedures like those presented here could estimate the number of samples that adequately represents soil hydraulic properties variability.

34-42

Authors: Sani Issa Mahaman Sanoussi , Fatondji Dougbedji , Ezenwa Matthew , A.A. Okhimamhe , Ali Ibrahim , Isiah Sule

In the Sahel, mineral fertilizer micro-dosing technique is known for its benefits to provide higher nutrient uptake and higher crop yields. A study was set up at ICRISAT research station at Sadoré in Niger, which aims at evaluating the sustainability of the technology in the long-term with emphasis on soil nutrients dynamics. The study has started since 2008 and was laid-out in a randomized complete block design that involved two pearl millet varieties, three planting densities, and four nutrients management options. For this study, a sub-set of the treatments from this long-term experiment was used. The nutrient management factor, which includes 4 levels was considered. The most important findings obtained indicated that the change in soil nutrient was markedly different on the planting hills and that from between hill. The change in soil pH-H2O values on the planting was -7.06 % for the control plots and -9.57 % for the plots applied with NPK. The total nitrogen content has dropped in the two different plots. The amplitude of drop has lowered with the application of NPK micro-dosing on the planting hills with respectively -5.11 % and -12.45 % in the control plots and the micro-dose plots. Positive change in available P was significantly observed (P≤0.05) in soil between hill with 1.08% in the control plots and 15.97 % in the amended plots. Both grain yield and total dry matter showed similar trend in which decreased yield was obvious over the time. In 2008, an average grain yield of 732 kg. ha-1 and 989 kg. ha-1 was obtained respectively for the control plots and 6g per hill of NPK plots. Whereas in 2016, 146 kg. ha-1 and 218 kg. ha-1 were produced respectively for the control plots and the mineral fertilizer micro-dosing plots. These findings indicated that in the Sahel low-input based millet cropping systems, for the mineral fertilizer micro-dosing technology to be sustainable in the long term, the improvement and maintenance of soil fertility should be considered as the cornerstone.

52-59

Authors: Nalan Kars , Imanverdi Ekberli

The aim of this study was to set regression models based on correlation between yield parameters of maize plant (height, thousand seed weight and yield) and physical and chemical characteristics of soils and to determine applicability of obtained models in estimation of plant yield grown in soils of Çarşamba Plain. Regression coefficient (R), root mean square error (RMSE), index of agreement , model efficiency (ME) were evaluated to determine the validity of regression models between the yield components and physical and chemical characteristics of 40 soil samples taken from root zone of cultivated farms. Model associated with the relation between (i) plant height and bulk density (BD), field capacity (FC), clay and sand content wasn’t statistical significant (R= 0.53, p>0.05); (ii) thousand seed weight and soil electrical conductivity (EC), organic matter (OM), lime (CaCO3), nitrogen (N), phosphorus (P), potassium (K), Ca + Mg was characterized with a moderate R (R=0.79, p < 0.05), and (iii) seed yield and OM, N, P, K, copper (Cu), cation exchange capacity (CEC), CaCO3 indices has the highest R (R = 0.87; p <0.01). In general, statistical parameters were within the validity limits. The established regression models can be applied for the predicting of yield parameters of maize plant grown in the farmed areas of the region.

66-74

Authors: Mehmet Ali Demiral , Juan Carlos Melgar , Beatriz Contreras , Ayako Kusakabe , Murat Uygun , Seçil Küçük Kaya

In this study, one-year old grapefruit trees grafted onto sour Orange (SO) and C22 rootstocks were exposed to NaCl-induced salinity (approx. 6 dS m-1) in pot culture for two months under greenhouse conditions. The experiment was laid out in a randomized block design with eight replicates. The trees were irrigated with saline solution containing 0.1% liquid fertilizer “Miracle-Gro Liqua Feed 9-4-9” (N-P2O5-K2O) enriched with micronutrients. The experimental treatments consisted of three levels (4 mM, 8 mM, 12 mM) of foliar applied proline along with control application. Distilled water served as the control. During the experiment the seedlings were sprayed totally five times with ten days intervals. At the end of the treatment physiologically mature leaves, free of damage or defects, were sampled. Dried and ground leaf samples were used for chemical (Na and Cl) and biochemical (DPPH scavenging activity, reducing power, total phenolic content, proline) analysis. Spesific leaf area, leaf water relations and leaf gas exchange of the plants were also determined. Foliar PRO application decreased Na and Cl concentrations of the leaves, and improved spesific leaf area in the final dose. Water leaf relations, photosynthetic activity and biochemical parameters were affected positively even though some differences were determined between the cultivars.