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The recent maize experiment commenced in the 2022 fall crop season at the District Al-Hussainiya, Kerbala, Iraq. The experiment comprised two factors, with the first factor a combination of different levels of nitrogen (0, 150, and 300 kg N ha-1) with corresponding labels, N0, N1, and N2, respectively, and three levels of potassium (0, 80, and 160 kg K ha-1) symbolized as K0, K1, and K2, respectively. The second factor was a foliar application of organic nutrients (potassium humate) with two concentrations (1 and 2 g L-1). The organic nutrient application occupied the main plots, while the inorganic fertilizer combinations were in the subplots. The experiment used the maize cultivar 'Sumer,' planted in clay mixed soil in a randomized complete block design (RCBD) with a split-plot arrangement and three replications. The results showed a significant effect of adding fertilizer combinations of nitrogen and potassium and foliar application of the organic nutrient potassium humate (2 g L-1) individually and in combinations in most growth, yield, and quality-related traits. The combination of inorganic and organic fertilizers also revealed a significant superiority in enhancing the plant height, number of leaves, ear length, grain rows per ear, grains per row, grain yield, and the percent oil and protein in the maize grains. The interaction between the two study factors contributed to reducing the used amount of mineral fertilizer to 50%, as there was no significant difference between the fertilizer combinations of nitrogen and potassium 150 N + 80 K and 300 N + 160 K kg ha-1 in addition with organic nutrient application at the rate of 2 g L-1. [ABSTRACT FROM AUTHOR]

To achieve the carbonization utilization of Triarrhena lutarioriparia straw and relieve the environmental pressure caused by improper disposal in the Dongting Lake area, the agricultural efficiency of biochar derived from Triarrhena lutarioriparia was clarified. Two typical paddy soils in southern China, namely reddish clayey soil developed from a Quaternary laterite parent material and granitic sandy soil developed from a granite parent material, were selected. Six treatments with different dosage of biochar (0, 1%, 2%, 4%, 6%, and 8% of the soil mass，0-20 cm soil depth) were set. Rice pot experiments were conducted in 2020 to study the effects of different application rates of Triarrhena lutarioriparia biochar on rice nutrient utilization characteristics in two typical soils. The results showed different application rates of Triarrhena lutarioriparia biochar and soil types had certain effects on dry matter accumulation and nutrient uptake by rice organs and aboveground structures. With the addition of biochar, compared with the treatment without biochar, the accumulation of dry matter of rice increased from 0.6% to 18.6% and from 15.5% to 42.4% in the granitic sandy soil and reddish clayey soil, respectively. With the addition of 4% biochar, the accumulation of nitrogen, phosphorus, and potassium nutrients in the rice plant of the treatment increased by 8.6%, 10.5%, and 82.5% in the granitic sandy soil and by 33.8%, 100.0%, and 125.3% in the reddish clayey soil, respectively. The quadratic regression equation and fertilizer – carbon coupling model fitting showed that the optimal addition amounts of biochar in the granitic sandy soil and reddish clayey soil were 2.51% and 4.80% for nitrogen utilization, 4.33% and 7.03% for phosphorus utilization, and 4.67% and 4.81% for potassium utilization, respectively. Therefore, the application of Triarrhena lutarioriparia biochar is conducive to promoting the accumulation and growth of nitrogen, phosphorus and potassium nutrients in rice, and the amount of biochar added and soil conditions are important factors affecting the coupling effect of fertilizer and carbon. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Soil Sciences & Agricultural Engineering is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A two-year experiment (2018 and 2019) was conducted to investigate the conjoint effect of applying rice straw as a soil mulch and treating snake cucumber (Cucumis melo var. flexuosus) plants by potassium silicate solution (4 mM) either by soaking seeds or by foliar applications for different periods, on soil fertility, vegetative growth and yield traits, antioxidant activities in plant, nutrient uptake, and total yield under heat stress conditions. The experiment was conducted during summer season (the maximum weekly temperature ranged from 35.8 to 40.6°C) on a clay soil at Dokki field under greenhouse conditions, Giza governorate, Egypt. The treatment of T5 (soaking seeds for 24 h in potassium silicate solution) combined with covering soil with rice straw gave superior effects on enhancing soil fertility and nutrient uptake, increasing chlorophyll content, increasing antioxidant enzymes activity, decreasing proline and other free amino acids (FAA), total soluble salts (TSS), and vitamin C content, and these were probably the reasons that increased the plant tolerance to face the stress. Total yield increased by 13.4 and 8.19% under rice straw soil cover. Also, its highest values were achieved by the treatment of T5 (173 and 200%), during the two tested seasons, respectively. Results of this study suggest that the conjoint effect of using rice straw as a soil cover and treating plants with potassium silicate solution (4 mM) by soaking their seeds for 24 h is beneficial for improving soil fertility, nutrient uptake as well as for crop production under heat stress conditions. [ABSTRACT FROM AUTHOR]

Cotton yield and quality are constantly deteriorating in water limited and poorly drained silty clay soils. Farmers practice deep plowing and irrigate at 2-week interval, which is costly, degrading soil, and reduce cotton yield. A field study was conducted to evaluate the impact of tillage, irrigation intervals, and K (potassium) levels on cotton yield and quality. The experiment comprised main plot [reduced tillage (RT) and conventional tillage (CT)], subplot [irrigation intervals (2, 3, and 4-week)], and sub-sub plot treatments [K levels (0, 50, 100, and 150 kg K ha−1)]. Experimental design was split-split-plot replicated thrice. RT with 4-week irrigation interval and K level can replace CT. RT with 4-week interval plus 150 kg K ha−1 produced 25.6% more returns than CT. Four-week interval with 150 kg K saved 50% water and showed higher lint yield than 2-week interval. Four-week interval increased lint yield by 41% and 15.7% over 2- and 3-week intervals, respectively. The highest K level improved lint quality and produced 50.9% higher lint yield than zero K level. Lint quality increased with deficit irrigation and higher K levels. Thus RT, infrequent irrigation, and appropriate K level is a sustainable approach for economic production of cotton. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Soil Sciences & Agricultural Engineering is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This experimental was carried out during the two winter seasons of 2019/2020 and 2020/2021 in a private unheated plastic houses,, Kom Haleen, Menia El Qamh District, Sharkia Governorate, Egypt, to study the effect of different sources of nitrogen fertilizer as soil application and some growth stimulants as foliar application on growth and yield of sweet pepper (cv. Lirica RZ) grown in clay soil using drip irrigation system. Results showed that, the interaction between fertilization sweet pepper plants with vermicompost at 1.225 kg/m² (as organic nitrogen 100%) and foliar spray with compost tea at 10 ml/l increased dry weight of leaves, stems and shoots/plant at 80 and 100 days after transplanting in both seasons, number of fruits/ plant and total yield/plant followed by the interaction between vermicompost and spraying with vermicompost tea at 7.5 ml/l. Generally, the interaction between fertilization of plants with vermicompost +FYM at 0.613+2.100 kg /m² as organic nitrogen (50% +50 % of each) and spraying with compost tea at 10 ml/l increased N,P and K in leaves and stems and average fruit weight. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Soil Sciences & Agricultural Engineering is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Canadian Shield clay soils are high in potassium (K) reserves. The differential contribution of soil K fractions to crop nutrition is an important issue for ley farming systems of Eastern Canada where nitrogen (N)‐based manure application rate leads to K surplus and redistribution. Our objective was to assess the long‐term change in K offtake, K budget, and K forms under a 3‐yr‐cycle ley farming system (barley [Hordeum vulgare]–mixed forage–mixed forage) initiated in 1989 and ended in 2016. The liquid dairy manure (LDM) supplied higher amounts of K than mineral fertilization (MIN) and led to larger K offtake across crop cycles. The cumulative K budgets averaged −579 kg K ha−1 cycle−1 for MIN and +69 kg K ha−1 cycle−1 for LDM. Despite cyclic variations, topsoil showed a surplus of exchangeable K (>100 kg K ha−1) at the end of experimentation under MIN and LDM compared to the initial state in 1989. Exchangeable and non‐exchangeable K fractions increased between 2001 and 2016 in 0‐ to 30‐cm depth even under K deficit (MIN), due to K release from slowly available forms and recycling from lower layers. There were no significant relationships between K budget and exchangeable K down to 90 cm. The approach relating soil exchangeable K and K budgets to support buildup and maintenance of soil fertility proved to be inappropriate in clay soils high in illite‐like minerals. Potassium dynamics in clay soils under ley farming highlighted the importance of considering non‐exchangeable and subsoil K in K fertilization recommendations. [ABSTRACT FROM AUTHOR]

Two field experiments were carried out at the experimental farm (Ghazala Village), Faculty of Agriculture, Zagazig University, Sharkia Governorate, during 2016/2017 and 2017/2018 seasons to study the influence of three planting densities, (28000, 35000 and 46666 plants/fad.) three levels of N fertilizer (80,100 and 120 kg/fad.) and two levels of potassium fertilizer (24 and 48 kg k2O/fad.) on yield and its attributes as well as quality of sugar beet grown in clay soil. Results of combined analysis illustrated that, decreasing planting density from 46666 to 35000 or 28000 plants/ fad., significantly increased root length, root diameter and fresh root weight g/plant; on the other hand the highest planting density (46666 plants/fad.) produced higher sucrose, extractable sugar percentages, sugar and recoverable sugar yields/fad., than low or medium densities. Raising N fertilizer levels significantly affected yield and its attributes as well as quality of sugar beet. Where, the results of the combined analysis indicated that, each increment of nitrogen fertilizer level from 80 up to 120 kg N/fad., cm was accompanied with a significant increase in root length, root diameter, fresh root weight/plant, root and recoverable sugar yields/fad., but significantly decreased sucrose (%). Data of combined analysis also revealed that application of 48 kg K2O/fad., significantly increased root yield attributes i.e., root length root diameter (cm), fresh root weight g/plant, sucrose, extractable sugar percentages, as well as, root and recoverable sugar yields ton/fad., compared with supply of 24 kg K2O/fad. Interactions between the studied factors (according to the combined analysis) indicated that the highest root yield (ton/fad.) was achieved when sugar beet was sown with the highest plant density of 46666 plants/fad., and fertilized with 120 kg N/fad. As well as, the highest value of root diameter (cm) was achieved under the application of 120 kg N/fad., and addition of 48 kg K2O/fad., while, the interaction between planting densities and potassium fertilizer levels had no significant effects on all studied traits. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Soil Sciences & Agricultural Engineering is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Potassium (K) is the most taken up and removed nutrient by potato (Solanum tuberosum L.), and has a great influence on tuber yield and quality. This study was performed to evaluate the effects of three rates (100, 200, and 400 kg K2O ha-1) and two timings of application of K (single application at planting furrow and split application of 50% at planting furrow plus 50% at hilling), as potassium chloride, as well as a control (without K application) on the plant nutrition and tuber yield and quality of potato 'Agata' grown in tropical clay soils. The split application of K fertilizer had little influence on plant nutrition and tuber yield and quality. The influence of K fertilization on increasing K and reducing Ca and Mg concentrations in the leaf was more significant in soil with low exchangeable K. In this soil, the maximum tuber yield (33.6 Mg ha-1; 107% higher than the control) was obtained with an estimated rate of 325 kg K2O ha-1, while in the soils with medium and high exchangeable K, the tuber yield was increased between 22 and 34% and only up to a rate of 200 kg K2O ha-1. The critical leaf K concentration to reach 95% of the maximum yield was 29.3 g K kg-1, but there was an extreme increase in the tuber yield even with K rates that provided leaf K concentrations above this limit. Potassium fertilization increased the firmness and reduced soluble solids and protein in tubers. [ABSTRACT FROM AUTHOR]

Lemon (Citrus limon), a species of the genus Citrus, is an economically significant crop and extensively cultivated in Iran, especially in Fars Province. Very little information is currently available on the changes in the different forms of soil potassium under the influence of lemon tree plantations or the associated mineralogical changes. The objective of this study was to investigate the status of different forms of K and the transformation of K-bearing minerals in the rhizosphere in lemon orchards of varying ages. Results demonstrated that the amounts of soluble, available, exchangeable, and nonexchangeable K in the control were higher than those in the lemon orchards of all the age range studied. The highest reduction in the different forms of soil K was measured for the 50-year-old orchard. The nonexchangeable K was significantly lower in the 20- and 50-year-old lemon orchards as compared with the control soil. Soil potassium concentration was observed to decrease with increasing soil depth. Our findings also indicated that vermiculitization of illitic clay minerals occurred due to both root potassium uptake and root activities in the rhizosphere of lemon trees. Shallower soil depths in the orchards were found to contain a higher illite content, while the vermiculite and interstratified I/S content increased with depth, except in the case of the 5-year-old orchard. Our findings also show that soils under lemon orchards of different ages exhibit differences in their K availability and, further, that vermiculitization might take place as a result of long-term cultivation despite the application of potassium fertilizers. [ABSTRACT FROM AUTHOR]

Despite the great importance of potassium applied as a fertilizer in the orange orchards, no information is currently available regarding the rate of potassium release from rhizosphere and the bulk soils of such trees. The objectives of this study were to investigate the weathering of micaceous minerals and their non-exchangeable K release and also, to examine the status of different forms of K in the rhizosphere and bulk soils of orange orchards with different ages in Darab, Fars Province. Samples were, accordingly, taken from the rhizosphere and bulk soils of orange orchards with the ages of 5, 10 and 20 years; also, virgin soils (control) were obtained from three soil depths including 0-30, 30-60, and 60-100 cm. Water soluble, exchangeable and nonexchangeable K, and the clay mineralogy of the soils were determined. The results demonstrated that the concentration of soluble and exchangeable K in the cultivated soils was less than that in the control soil and that the concentration of nonexchangeable K in the soils of 20-year-old orchards was less, than that in other soils. Soluble and exchangeable K values decreased with depth in all soils. Clay mineralogy investigation also showed that the quantity of illite decreased and that of smectite and illite-smectite increased as the age of orange trees was raised. With increasing the age of orange trees and root development, more potassium could be taken up from soil and more changes occurred in the soil minerals. In order to avoid a very high decline in the reserved K in the soils under orange trees, particularly in the orchards with older trees, K fertilization has to be taken more seriously based on the soil testing results. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted under greenhouse condition at the Experimental Farm, Faculty of Agriculture, Zagazig University, Egypt. The experiment aimed to study the effect of different potassium sources (potassium sulphate and potassium feldspar) at the recommended rate (40 mg K kg-1) either single or in combination with soil amendments i.e., farmyard manure (FYM) and sulfur (S) with or without silicate dissolving bacteria (SDB) on yield and nutrients uptake by wheat through the investigated clayey soil. Soil were taken from the surface layers (0-30 cm) from Hehia District, Sharkia Governorate, Egypt. Application of K-sulphate or K-feldspar as individual application or combined with different soil amendments under SDB gave increase in straw and grain yield, potassium uptake, biological yield, 1000 grain weight and protein content of wheat plants compared to untreated soil. The highest value for each of yield, K-uptake and available K was found in clayey soil treated with K-sulphate combined with FYM plus S in the presences of SDB, while the lowest ones were obtained with untreated soils in absence of soil amendments and SDB. Application of Ksulphate showed greater value in each of yield, protein content, K-uptake by wheat plants and soil available potassium than K-feldspar. Application of SDB to K-sulphate or K-feldspar increased yield, protein content, K-uptake of wheat and available potassium compared to the untreated ones. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Plant Production is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Soil organic carbon (SOC) sequestration in response to long-term fertilizer management practices under jute-rice-wheat agro-ecosystem in alluvial soils was studied using a modeling approach. Fertilizer management practices included nitrogen (N), phosphorus (P) and potassium (K) fertilization, manure application, and root-stubble retention of all three crops. Soil carbon (C) model RothC was used to simulate the critical C input rates needed to maintain initial soil C level in long timescale (44 years). SOC change was significantly influenced by the long-term fertilizer management practices and the edaphic variable of initial SOC content. The effects of fertilizer combination "100%NPK+FYM" on SOC changes were most significant over "100%NPK" fertilization. If the 100% NPK fertilizer along with manure applied with stubble and roots retention of all crops, alluvial soils of such agro-ecosystem would act as a net C sink, and the average SOC density kept increasing from 18.18 Mg ha−1 during 1972 to the current average of ∼22 Mg ha−1 during 2065 s. On an average, the critical C input was estimated to be 5.30 Mg C ha−1 yr−1, depending on local soil and climatic conditions. The critical C input could be effectively estimated using a summary model driven by current SOC level, mean annual temperature, precipitation, and soil clay content. Such information will provide a baseline for assessing soil C dynamics under potential changes in fertilizer and crop residues management practices, and thus enable development of management strategies for effectively mitigating climate change through soil C sequestration. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Soil Sciences & Agricultural Engineering is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Soil Sciences & Agricultural Engineering is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The extractable soil-K concentration, used for fertilizer-K recommendations, may be affected by soil drying. Although air or oven drying are the most common soil processing methods, K from field-moist soil has been documented to be a better predictor of soil-K availabilities and fertilizer-K needs for soybean [Glycine max. (L.) Merr.] grown on fertile silt loam to clayey soils. We evaluated the effect of four soil processing methods (field-moist [FM], air-dry [AD], air-dry followed by oven-dry [ADOD], and oven-dry [OD]) in predicting extractable soil-K availability for soybean production on less fertile Mid-Atlantic sandy-textured soils. Twelve soybean field trials were conducted in 2014 on Coastal plain and piedmont soils in Virginia and North Carolina. Soil K was extracted by Mehlich-1 with each soil processing method and correlated with soybean relative yield. Soil-K concentrations from each method were statistically similar and strongly correlated (r² = 0.94-0.98) with each other having intercept and slope coefficients that were not different from zero and one, respectively. Extractable soil-K concentrations from each method were also strongly correlated with soybean relative yield and explained 93 to 95% of the relative yield variation for FM soil, 95 to 96% for AD soil, 83 to 86% for ADOD soil, and 94 to 95% for OD soil. Results suggest that soil-K concentrations from FM, AD, and OD samples are similar in predicting K availability for soybean. Soil drying should not be an issue of concern in extracting soil K and recommending fertilizer-K rate for soybean production on Mid-Atlantic coarse-textured Coastal Plain and Piedmont soils. [ABSTRACT FROM AUTHOR]

Clay amendments are used widely in the horticultural industry in peat-based substrates, as they have the capability to improve the potassium (K) buffering capacity. The K adsorption and desorption behavior of different clays was characterized here to develop criteria for identification of clays suitable for substrate amendment and to evaluate their significance for plant K uptake. K adsorption of saprolitic, bentonitic and relocated clays from the Westerwald area, Germany, was characterized with adsorption isotherms for calculating the maximum adsorption capacity for K. The K desorption was quantified in a percolation experiment using 0.01 M CaCl 2 as extractant. The influence of a varying K adsorption capacity of the clays on the K availability to plants was investigated in a growth experiment. The availability of K in substrates was determined by 0.01 M CaCl 2 (CAT), Ca-acetate-lactate and NH 4 acetate. Different cultivation practices were simulated by varying the start of K topdressing: “immediate,” “delayed” and “no” K topdressing. A higher K adsorption capacity of the clays amended resulted in a lower K concentration in the pore solution of clay-amended peat-based substrates, while the CAT extractable K concentration was the same. It also resulted in an enhanced plant growth and higher K concentrations in the shoot without K topdressing. The uptake of K by plants exceeded the amount of exchangeable K in some peat-clay blends where no K was fertilized. The amount of K released from the clays in the plant experiments was in the same magnitude as the maximal desorbable K determined in the percolation experiment and was highly dependent on the mineralogical composition in the order: smectitic > illitic, kaolinitic clay. The K released from the clays contributed significantly to the supply of K to plants. [ABSTRACT FROM AUTHOR]

Nutrient demand for oil palm is determined by the potential yield, which is varies according to genotype, soil, palm age and environmental factors. Moisture stress having a strong influence on oil palm growth and development. Therefore, a study was conducted to determine the effect of nitrogen (N), phosphorus (P) and potassium (K) fertilizers on growth performance and yield response of oil palm in irrigation system. This study using 33 NPK factorial fertilizer design were conducted on mature D × P palms planted on Gong Chenak soil series (Aquic kandiudults) at Felda Agricultural Services Sdn. Bhd. (FASSB), Tembangau 9 estate (03°00′59.5″N Longitude 102°28′48.5″E) in the year 2000 under irrigation condition. The fertilizer rates for respective fertilizers (kg nutrient/palm/year) were N (0, 0.84, and 1.68 kg N), P (0, 0.68, and 1.36 kg P 2 O 5) and K (0, 0.24, and 4.8 kg K 2 O). A normal field operation and maintenance for the oil palm was used throughout 7-year (2005–2012) study period. Mature oil palms treated with complete NPK fertilizer (N1P1K1 and N2P2K2) increased 17.3% in an average fresh fruit bunch yield (FFB) from 22.9 ton/ha/year in control plot to 27.0 ton/ha. The results of this study highlighted the positive response of palm growth and foliar nutrient status with N manuring throughout this study period. Fertilizer rate at 0.84 N, 0.68 P 2 O 5 , and 2.4 kg K 2 O was the best rate to maintain optimum palm growth, particularly on estimated leaf area index (LAI) and frond dry weight, FFB yield response and foliar nutrient status. • Oil palm crops in plantation sector have never been irrigated. • Nitrogen, phosphorus and potassium status in oil palm showed improvement in treated plot as compared control. • About 17.3% increase in fresh fruit bunch yield to 27.0 mt/ha/yr in plot treated with complete NPK fertilizer compared to control (22.9 mt/ha/yr). • Fertilizer rate at 0.84 N, 0.68 P 2 O 5 , and 2.4 kg K 2 O was the best rate to maintain optimum palm growth, yield response and foliar nutrient contents. [ABSTRACT FROM AUTHOR]

Aims: Potassium (K) fertilization increases crop productivity, but in some cases, crop productivity is maintained even with inadequate or low K input. In both situations, the soil mineralogy plays a role that should be investigated. The aims of this study were to quantify the potassium concentrations in several soil compartments, determine the amount of K taken up by plants, and consider soil clay mineralogical changes and K dynamics, as response to K fertilization historic and successive crops. Methods: A soil field experiment was conducted in south Brazil over a period of 15 years with different K doses, and a second experiment was conducted in a greenhouse with 11 successive plant cycles under two conditions: no K fertilization (K-poor context) and K fertilization of 30 and 90 mg kg of soil (K-rich context). Results: In the K-poor context, illite was not found in clay fraction and the non-exchangeable K and available K forms were reduced, compromising both the K uptake by plants and the crop yield. In the K-rich context, the low amount of illite was found compared to K-poor context, while relative hydroxy-aluminum interlayered vermiculite (HIV) abundance decreased in detriment of kaolinite. Furthermore, all K compartments (K in plants, available K, structural K, and non-exchangeable K) were restored when high fertilization was applied to the soil. Conclusion: For correct fertilization, the soil mineralogy and fertilization background should be taken into account to obtain high crop production and low K loss in agricultural lands. This will help to maintain soil K reserve, but the successive crops induce ion exhaustion, including K, affecting whole clay mineral assemblage. [ABSTRACT FROM AUTHOR]

The five representative soil pedons were studied for characterization and evaluate for soil-site suitability for groundnut in the soils of Uben Irrigation Command Area of Saurashtra region in Gujarat. All the soils were found dominance of clay (26.4 to 39.8 per cent) and finer in texture. The soils were found clay loam to clayey in texture. The soils are moderately alkaline reaction and calcareous in nature. The soils were found low in available nitrogen, medium in phosphorus and high in potash content. The soils of Vertic Calciustepts [Minor-1, Bava Pipalia (P1) and Minor-4, Arabtimbadi (P2)], Vertic Haplustepts [Minor-6, Arabtimbadi (P3)] and Lithic Ustorthents [RBMC, Pipalva (P4)] and Typic Haplustepts (Minor-9, Chowki(P5) are moderately suitable (S2) for groundnut cultivation. The soil-site characteristics such as drainage, texture and soil fertility appeared to be most striking factors influencing the crop response. [ABSTRACT FROM AUTHOR]

Annual potassium (K) balances have been calculated over a 40-year period for five field experiments located on varying parent materials (from loamy sand to clay) in south and central Sweden. Each experiment consisted of a number of K fertilizer regimes and was divided into two crop rotations, mixed arable/livestock (I) and arable only (II). Annual calculations were based on data for K inputs through manure and fertilizer, and outputs in crop removal. Plots receiving no K fertilizer showed negative K balances which ranged from 30 to 65 kg ha−1 year−1 in rotation I, compared with 10–26 kg ha−1 year−1 for rotation II. On sandy loam and clay soils, the K yield of nil K plots (rotation I) increased significantly with time during the experimental period indicating increasing release of K from soil minerals, uptake from deeper soil horizons and/or depletion of exchangeable soil K (Kex). Significant depletion of Kex in the topsoil was only found in the loamy sand indicating a K supply from internal sources in the sandy loam and clay soils. On silty clay and clay soils, a grass/clover ley K concentration of ∼2% (dry weight) was maintained during the 40-year study period on the nil K plots, but on the sandy loam, loam and loamy sand, herbage concentrations were generally less than 2% K. [ABSTRACT FROM AUTHOR]