Sequestration of P fractions in the soils of an incipient ferralisation chronosequence on a humid tropical volcanic island

Background Phosphorus (P) is the limiting nutrient in many mature tropical forests. The ecological significance of declining P stocks as soils age is exacerbated by much of the remaining P being progressively sequestered. However, the details of how and where P is sequestered during the ageing in tropical forest soils remains unclear. Results We examined the relationships between various forms of the Fe and Al sesquioxides and the Hedley fractions of P in soils of an incipient ferralitic chronosequence on an altitudinal series of gently sloping benches on Green Island, off the southeastern coast of Taiwan. These soils contain limited amounts of easily exchangeable P. Of the sesquioxide variables, only Fe and Al crystallinities increased significantly with bench altitude/soil age, indicating that the ferralisation trend is weak. The bulk of the soil P was in the NaOH and residual extractable fractions, and of low lability. The P fractions that correlated best with the sesquioxides were the organic components of the NaHCO3 and NaOH extracts. Conclusions The amorphous sesquioxides, Feo and Alo, were the forms that correlated best with the P fractions. A substantial proportion of the labile P appears to be organic and to be associated with Alo in organic-aluminium complexes. The progression of P sequestration appears to be slightly slower than the chemical and mineralogical indicators of ferralisation.

Effect of Bioslurry from Fixed Dome and Tubular (Flexi) Biodigesters on Selected Soil Chemical Properties, Maize (Zea mays) Growth, Yield and Quality

Agricultural utilization of bioslurry plays a critical role in soil conditioning and hence crop production. It also reduces greenhouse gas emissions thus mitigating climate change. Although the effect of bioslurry on growth and yields is well researched, that of different biodigester types is under-researched. Therefore, a study was carried out in Waruhiu Agricultural Training Centre, Githunguri sub-county, Kiambu county in Kenya, to investigate the effect of bioslurry from flexi and dome biodigesters on soil chemical properties, maize growth, yield and grain quality. Treatments were laid out in a Randomized Complete Block Design (RCBD) and replicated three times. The treatments were bioslurry from both Fixed Dome and Flexi biodigesters, applied separately at a rate of 400mls per hill as basal and top dress fertilizer. Planting was done during the 2019 short and 2020 long rains, using Duma 43 maize variety. The agronomic (germination percentage, number of leaves, leaf width, leaf length, plant height) and productivity data (stalk, stovers, grain yields and grain quality) were subjected to analysis of variance (ANOVA) through Proc general linear model (GLM) procedures. Mean separation was done using least square means (LS-Means). Results showed an increase in soil pH, total N and OC, exchangeable P, K, Mn and Na in both biodigester types. Total N and OC were higher in Dome treated soils by 38.89% and 37.00%, while in Flexi, it was 16.67% and 16.00% respectively. Exchangeable P and K was higher in Flexi treated soils with a 38.57% and 50.00% increase while in Dome it 37.86% and 47.22% respectively. Magnesium and Zn decreased after treatment by 34.30% and 22.59% in Dome while Flexi had 33.23% and 31.79% increase. Exchangeable Fe and acidity decreased in Dome but increased in Flexi treated soils. No statistical differences were observed on growth and yield parameters but Dome registered higher grain yields by 9.4% and 6.3% for short and long rains respectively. Flexi treated soils registered higher values in most grain nutrient content such as K, Fe, Cu, Mn and Zn in short rains and P, Ca, Fe, Cu, Mn and Zn in the long rains. Bioslurry from both biodigester types variably increased the evaluated soil chemical properties but decreased Mg and Zn. Despite the numerical differences noted between bioslurry from both biodigester types on maize growth and yield, there was no significant difference (p≤.05). However, Dome bioslurry increased N, OC and maize grain yield more while exchangeable P and K and most of the grain nutrient content were higher in Flexi treated soils. Therefore, bioslurry from either biodigester type can be used in enhancing soil conditions, growth, yield and quality of maize. However, a long-term experiment is required validate the findings.

Characterisation of soil phosphorus forms in the soil-plant system using radioisotopic tracer method

Soil incubation and pot experiments were conducted to follow the sorption processes of added phosphorus (P) fertiliser using the radioisotope tracer technique. Increasing doses of P fertiliser (40, 80, 160, 320 mg P/kg soil) were added to Chernozem and Arenosol and incubated for 1, 3, and 13 weeks. After incubation, perennial ryegrass (Lolium perenne L.) was sown in one group of pots, and the experiment had been continuing for another 9 weeks. The yield, grass P uptake, isotopically exchangeable (P_IE), water-soluble (P_W), and ammonium lactate soluble phosphorus (P_AL) fractions of soils were measured. On Chernozem, plant P uptake, P_IE, P_W and P_AL were significantly less in the case of the longest incubation period compared to shorter incubations. This suggests a transformation of P into tightly sorbed form. On Arenosol, there were only small changes in the parameters as the incubation period increased, suggesting less intense P transformation to tightly sorbed form. The P_W/P_IE ratio enhanced with increasing P-doses, and the ratios were higher on Arenosol. On Arenosol, the higher P doses caused a greater increase of P_W than on Chernozem. The P_IE + P_W showed a good correlation with plant P uptake proving this value can be a good indicator of plant-available phosphorus.

Spatial variability of some chemical properties of a Cambisol soil with cocoa (Theobroma cacao L.) cultivation

Objective: To evaluate the spatial variability of some chemical properties of a Cambisolsoil, in order to establish specific agronomic management zones for cocoa cultivation.Methodology: A sampling of 42 georeferenced points equidistant at 40 m was carriedout. Geostatistical variability maps were made with the results of the chemical analysisof the soil properties, using the ordinary Kriging interpolation technique.Results: It was found that the percentage of saturation of acidity (PSA), acidity and H+showed high variability; P-Olsen and interchangeable K, Ca and Mg displayed mediumvariability, and pH, MO, CIC and Al presented low variability. Soil properties pH, PSA;Exchangeable P-Olsen, Ca and Mg showed high spatial dependence (<25%) and OM,exchangeable K and CIC moderate spatial dependence (25-75%).Study limitations / Implications: The generated maps allowed the identification ofpartial areas with different variability, as well as the direction of greatest variability of theproperty as a function of distance.Conclusions: With the maps, it was possible to make recommendations for agronomicmanagement depending on each specific management area.

Soil phosphorus fractionation in calcareous soil as affected by organic amendments application

<p>Understanding of P transformations following organic amendments addition to highly calcareous soils is necessary for developing better management practices that can help enhance P fertilizer use efficiency. Phosphorus solubility and availability for plant uptake under the conditions of arid calcareous soil is very low, making P nutrient supply a critical issue under these conditions. The aim of this study was to evaluate the impact of various types of organic amendments (chicken compost, cow compost and a mixture of humic-fulvic acid) applied alone at different rates of KH2PO4 fertilizer on P fractions in calcareous soil using the sequential chemical extraction method. Amended calcareous soil was incubated under laboratory conditions and soil samples were collected at 0, 4, 8 and 16 weeks of the incubation periods. Soil was sequentially extracted and analyzed for P different fractions. The results indicated that the addition of chicken and cow compost increased soluble and exchangeable-P and Ca-P fractions in calcareous soil and the increases depend on application rates. The results indicated that combination of chicken and cow compost with different KH2PO4 fertilizer application rates increased the concentration of soluble and exchangeable-P in the soil compared to organic amendments or KH2PO4 fertilizer applied alone. The P associated with Ca was the dominant P fractions in soil, ranging between 51 to 59% regardless of the different treatment and the period of incubations. The Al- and Fe-associated P fractions varied between 2 and 9%, with the maximum value being observed at the eighth week of incubation. The residual-P fraction ranged between 5 and 22% at different incubation periods.</p>

Measuring the Fate of Compost-Derived Phosphorus in Native Soil below Urban Gardens

The heavy reliance on compost inputs in urban gardening provides opportunities to recycle nutrients from the urban waste stream, but also creates potential for buildup and loss of soil phosphorus (P). We previously documented P in leachate from raised-bed garden plots in which compost had been applied, but the fate of this P is not known. Here, we measured P concentrations in soils below four or six-year-old urban garden plots that were established for research. We hypothesize that the soil P concentration and depth of P penetration will increase over time after gardens are established. Soil cores were collected in five garden plots of each age and quantified for inorganic weakly exchangeable P. Inorganic weakly exchangeable P was significantly elevated in native soil below garden plots (>35 cm deep) relative to reference soil profiles, and excess P decreased with increasing depth, although differences between garden plots of different ages were not significant. Our analysis shows that excess P from compost accumulates in native soil below urban garden plots. While urban agriculture has the potential to recycle P in urban ecosystems, over-application of compost has the potential to contribute to soil and water pollution.

Especiación del fósforo en sedimentos de un río tropical venezolano y su posible impacto sobre el ecosistema

In this study, a modification of the method of extraction sedimentary(SEDEX) was used to quantify the different forms of P in sediments collected inCuchivero river during March 2014. The range of variation of the concentrations ofthe different forms of P respect the total P (TPf) were 4.84-7.49 μgP/g to the F1 fraction consisting of exchangeable P (ad-P) plus associated with iron oxides (Fe-P)with greater preponderance of P-Fe; 0,58-1,61 μgP/g- authigenic (F2); 2.03 - 6.38μgP/g- detrital (F3), and 28.59 - 68.99 μgP/g-organic (F4), respectively. Thesevalues represent promedio11, 54%; 1.62%; 7.67% and 79.08% respectively for thefour fractions. The organic phosphorus was the way most representative fractionspeciation of TPf. The average percentage of bioavailable P represented by F1 + F4fraction of P was 52.72 μg-P/g, which represents 90.63% of the TPf. Thedistribution of the different forms of P in sediments showed association withsmaller particle size and postdepositional different mechanisms may be affected bysources of input materials, grain size, depositional environments, hydrologicalconditions and anthropogenic activities.

Effect of green manure crops, termination method, stubble crops, and fallow on soil water, available N, and exchangeable P

Green manure crops may have a role to play in the development of sustainable agricultural systems in the semiarid northern Great Plains of North America. This study determined the benefits of different green manure crops, seeding dates, and termination methods on soil nitrogen, phosphorus, and moisture, as well as the performance of durum wheat following green manures the following year. Field experiments were conducted at Swift Current, Saskatchewan, from 2006 to 2009. Three green manure crops [forage pea (Pisum sativum L.), chickling vetch (Lathyrus sativus L.), and black lentil (Lens culinaris Medik.)] were seeded in May, June, and July, and terminated at full bloom using glyphosate, rototilling or by frost. Other treatments included summerfallow and stubble of selected crops harvested for grain or silage. Different green manure crops, seeding dates or termination methods had similar effects on soil moisture, available N, and exchangeable P at termination or the following spring. These effects of green manure management on soil residual characteristics were comparable to those observed under summerfallow, but higher than those on grain or silage stubble. Therefore, green manure is a viable alternative to summerfallowing and could be seeded any time during the growing season. If seeded late, green manure could be terminated by frost, thus saving on costs.

Study of salinity effects on the inorganic phosphorus transformation in three different soil series of Ganges River Floodplain

The present study was carried out to investigate the effects of salinity level on different forms of inorganic phosphorus (P) transformation in three different soil series such as Amjhupi, Gopalpur and Bajoa located in Ganges River Floodplain. Two non-saline soils and one slightly saline soil with different textural classes were collected from these sites. The salinity treatments were 0, 6, 10 and 13 dSm-1 with three replications. The treated soils were then incubated in laboratory at field capacity moisture condition. To determine the transformation of different forms of inorganic P, sampling was done for 0, 14, 21, 42 and 84 days. Different forms of inorganic P such as soluble and exchangeable phosphorus (SE-P), iron and aluminium bound phosphorus (Fe and Al-P), calcium bound phosphorus (Ca-P) and residual phosphorus (RE-P) were determined. For Amjhupi soil series, the sequence of different forms of inorganic P was RE-P>Ca-P>Fe and Al-P>SE-P according to their amount. For Gopalpur and Bajoa soil series, the sequence was Ca- P>RE-P>Fe and Al-P>SE-P and RE-P>Ca-P>Fe and Al-P>SE-P, respectively. The sequence clearly indicates that the soluble and exchangeable P decreases with time due to salinity which reduces the uptake of P and ultimately reduces the yield. The changes were statistically significant (p<0.0001) in case of all three soils.Jahangirnagar University J. Biol. Sci. 5(1): 71-79, 2016 (June)

PENGARUH KEDALAMAN MUKA AIR TANAH TERHADAP LILIT BATANG KARET CLON PB260 DAN SIFAT KIMIA TANAH GAMBUT DI KEBUN MERANTI RAPP RIAU

Study to evaluate the effect of the depth of water table in peatlands of the PB260 rubber girthimmature plants (age 2-3 years) and chemical properties of peat soil has been carried out inMeranti Estate RAPP Kampar Estuary Pangkalan Kerinci District of Riau in December 2013.The research used a descriptive method with measuring water table depth in selected plots with girthmeasurements of planting rubber trees planted in 2010 and 2011. At two sample plots (representingthe shallowest water level and water level deep) dug each soil profile to the investigation anddecision soil samples. Soil samples were analyzed at the Laboratory of BPTP North Sumatra. Theresults showed that the water table in peatlands deeper, reaching 88.6 cm girth will decrease thegrowth of young rubber trees. Rubber immature plants age 2 years who has the best girth growth ingroundwater at a depth of 29.6 cm deep and 3 years old trunk circumference rubber girth bestgrowth at 65.3 cm water table. The water table is within reach mean 88.6 cm cause fasterdecomposition of peat soil is characterized by C/N ratio of lower and lower quality (fertility) peatsoils with lower ash content, K-exchangeable, Mg-exchangeable, P-available, and P-total.