Effect of Saline Water on Soil Acidity, Alkalinity and Nutrients Leaching in Sandy Loamy Soil in Rwamagana Bella Flower Farm, Rwanda

The necessity to saline and sodic waters is sometimes used for irrigating agricultural activities under certain circumstances, but it is important to note that the use of these waters comes with specific considerations and limitations. One way to decrease undesirable effects of sodic waters on the physical and chemical properties of soils is to apply organic and chemical amendments within the soil. This study aimed to assess the effectiveness of saline water on soil acidity, alkalinity and nutrients leaching in sandy loamy soil at Bella flower farm, in Rwamagana District, Rwanda. The water used was from the Muhazi Lake which is classified as Class I (Saline water quality). Column leaching experiments using treated soils were then conducted under saturated conditions. The soil under experimental was first analyzed for its textural classification, soil properties and is classified as sandy loamy soil. The t-test was taken at 1%, 5% and 10% levels of statistical significance compared to control soil. The results indicated that the application of saline water to soils caused an increase in some soil nutrients like increase of Phosphorus (P), Potassium (K+), Magnesium (Mg2+), Sulphur (S), CN ratio and Sodium (Na+) and decreased soil texture, physical and chemical properties and remained soil nutrients. Consequently, the intensive addition of saline water leachates to soil in PVC pipes led to decreased of soil EC through leaching and a raiser Soluble Sodium Percentage (SSP). The rate of saline water application affected the increase accumulation of SAR and Na% in the top soil layers. The study indicated that saline water is an inefficient amendment for sandy soil with saline water irrigation. The study recommends further studies with similar topic with saline water irrigation, as it accentuated the alkalinity levels.

Reduction of N2O emissions by DMPP depends on the interactions of nitrogen sources(digestate vs. urea) with soil properties

The inhibition of nitrification by mixing nitrification inhibitors(NI)with fertilizers is emerging as an effective method to reduce fertilizer-induced nitrous oxide(N_(2)O)emissions.The additive 3,4-dimethylpyrazole phosphate(DMPP)apparently inhibits ammonia oxidizing bacteria(AOB)more than ammonia oxidizing archaea(AOA),which dominate the nitrification in alkaline and acid soil,respectively.However,the efficacy of DMPP in terms of nitrogen sources interacting with soil properties remains unclear.We therefore conducted a microcosm experiment using three typical Chinese agricultural soils with contrasting pH values(fluvo-aquic soil,black soil and red soil),which were fertilized with either digestate or urea in conjunction with a range of DMPP concentrations.In the alkaline fluvo-aquic soil,fertilization with either urea or digestate induced a peak in N_(2)O emission(60μg N kg^(-1)d^(-1))coinciding with the rapid nitrification within 3 d following fertilization.DMPP almost eliminated this peak in N_(2)O emission,reducing it by nearly 90%,despite the fact that the nitrification rate was only reduced by 50%.In the acid black soil,only the digestate induced an N_(2)O emission that increased gradually,reaching its maximum(20μg N kg^(-1)d^(-1))after 5–7 d.The nitrification rate and N_(2)O emission were both marginally reduced by DMPP in the black soil,and the N_(2)O yield(N_(2)O-N per NO2–+NO3–-N produced)was exceptionally high at 3.5%,suggesting that the digestate induced heterotrophic denitrification.In the acid red soil,the N_(2)O emission spiked in the digestate and urea treatments at 50 and 10μg N kg^(-1)d^(-1),respectively,and DMPP reduced the rates substantially by nearly 70%.Compared with 0.5%DMPP,the higher concentrations of DMPP(1.0 to 1.5%)did not exert a significantly(P<0.05)better inhibition effect on the N_(2)O emissions in these soils(either with digestate or urea).This study highlights the importance of matching the nitrogen sources,soil properties and NIs to achieve a high efficiency of N_(2)O emission reduction.

Influence of Soil pH, Organic Matter, and Clay Content on Environmentally Available Lead in Soils: A Case Study in Muncie, Indiana, USA

Due to historical and ongoing industrial practices, lead contamination in urban soils presents substantial health risks, primarily due to its capacity to readily migrate from the soil to humans. This research focused on the influence of soil pH, organic matter, and clay content on extractable lead amounts. Sixty-four soil samples from Muncie, Indiana, were analyzed, revealing that the examined factors accounted for 21.71% of the Pb mg/Kg-dry variable variance (p −0.4, p < 0.001), with XRD and FTIR analyses confirming the binding affinity of clay minerals with lead. In contrast, no significant relationships were found between Pb concentrations and soil pH (r = 0.07;p = 0.59) or organic matter content (r = 0.12;p = 0.34). Elucidating the interactions between lead, clay minerals, and other soil constituents is crucial for addressing lead-contaminated soils and reducing environmental and health impacts.

Effects of fencing on vegetation and soil restoration in a degraded alkaline grassland in northeast China

In order to restore a degraded alkaline grassland, the local government implemented a large restoration project using fences in Changling county, Jilin province, China, in 2000. Grazing was excluded from the protected area, whereas the grazed area was continuously grazed at 8.5 dry sheep equivalent（DSE）/hm2. In the current research, soil and plant samples were taken from grazed and fenced areas to examine changes in vegetation and soil properties in 2005, 2006 and 2008. Results showed that vegetation characteristics and soil properties improved significantly in the fenced area compared with the grazed area. In the protected area the vegetation cover, height and above- and belowground biomass increased significantly. Soil pH, electrical conductivity and bulk density decreased significantly, but soil organic carbon and total nitrogen concentration increased greatly in the protected area. By comparing the vegetation and soil characteristics with pre-degraded grassland, we found that vegetation can recover 6 years after fencing, and soil pH can be restored 8 years after fencing. However, the restoration of soil organic carbon, total nitrogen and total phosphorus concentrations needed 16, 30 and 19 years, respectively. It is recommended that the stocking rate should be reduced to 1/3 of the current carrying capacity, or that a grazing regime of 1-year of grazing followed by a 2-year rest is adopted to sustain the current status of vegetation and soil resources. However, if N fertilizer is applied, the rest period could be shortened, depending on the rate of application.

Modeling the contribution of abiotic exchange to CO_2 flux in alkaline soils of arid areas

Recent studies on alkaline soils of arid areas suggest a possible contribution of abiotic exchange to soil CO2 flux(Fc).However,both the overall contribution of abiotic CO2 exchange and its drivers remain unknown.Here we analyzed the environmental variables suggested as possible drivers by previous studies and constructed a function of these variables to model the contribution of abiotic exchange to Fc in alkaline soils of arid areas.An automated flux system was employed to measure Fc in the Manas River Basin of Xinjiang Uygur autonomous region,China.Soil pH,soil temperature at 0–5 cm(Ts),soil volumetric water content at 0–5 cm(θs)and air temperature at10 cm above the soil surface(Tas)were simultaneously analyzed.Results highlight reduced sensitivity of Fc to Ts and good prediction of Fc by the model Fc=R10Q10(Tas–10)/10+r7q7(pH–7)+λTas+μθs+e which represents Fc as a sum of biotic and abiotic components.This presents an approximate method to quantify the contribution of soil abiotic CO2 exchange to Fc in alkaline soils of arid areas.

Studies on Fast Remediation of Soda Meadow Alkaline Soil

Researches on models of remediation quickly in soda meadow alkaline soil, and dynamic variation of water-salt in saline soil of Zhaozhou County were studied systematically from 2001 to 2006. Realize the vegetation cover of those years through the artificial planting, mixed seeding lyme grass （Elymus dahuricus Turcz） and melilot in the mode of rotary tillage and deep loosening in lower and medium saline soils. The results showed that there was remarkable relationship between net evaporation （difference of precipitation and evaporation） and total salt content in the soil. The net evaporation could be used as a new method to forecast the dynamics variation of salt to ensure the pasture optimum sowing time. Realize the autumnal vegetation cover of those years through direct planting on the bourgeon layer of soda meadow alkaline soil, on the other hand, the covered pasture made the function of restraining salt and alkaline content to realize the biology reverse succession quickly. Forage seeds were seeded directly on the seeding bed of soda alkaline meadow at the end of July. In fall of the same year, a certain amount of biomass was obtained. The model, which has remarkable economical efficiency and use widely, represented the innovative model for the fast vegetation restoration on the soda alkaline meadow soil.

Effects of Irrigation with Well Water on Chemical Characteristics of a Weakly Alkaline Soil Used as Rice Field

This paper discussed the effects of irrigation with well water on the salinity and pH of a weakly alkaline paddy soil in Fujin of Heilongjiang Province in the north-eastern part of China.It has been found that after seven years the accumulation of total soluble salts did not occur and that the pH of 0～15 cm layer fell down from 7.92～8.30 to 6.76～7.45,and that the content of anion HCO - 3 and its proportion in the total soluble anions have fallen down.Conversion from paddy soil to upland restored the pH of soil,exchangeable sodium,ESR(exchangeable sodium ratio) to their original levels of upland fields respectively.

Comparative Effects of Salt Stress and Extreme pH Stress Combined on Glycinebetaine Accumulation,Photosynthetic Abilities and Growth Characters of Two Rice Genotypes

Glycinebetaine （Glybet） accumulation, photosynthetic efficiency and growth performance in indica rice cultivated under salt stress and extreme pH stress were investigated. Betaine aldehyde dehydrogenase （BADH） activity and Glybet accumulation in the seedlings of salt-tolerant and salt-sensitive rice varieties grown under saline and acidic conditions peaked after treatment for 72 h and 96 h, respectively, and were higher than those grown under neutral pH and alkaline salt stress. A positive correlation was found between BADH activity and Glybet content in both salt-tolerant （P=0.71） and salt-sensitive （P=0.86） genotypes. The chlorophyll a, chlorophyll b, total chlorophyll and total carotenoids contents in the stressed seedlings significantly decreased under both acidic and alkaline stresses, especially in the salt-sensitive genotype. Similarly, the maximum quantum yield of PSII （Fv/Fm）, photon yield of PSII （ФPSII）, non-photochemical quenching （NPQ） and net photosynthetic rate （Pn） in the stressed seedlings were inhibited, leading to overall growth reduction. The positive correlations between chlorophyll a content and Fv/Fm, total chlorophyll content and ФPSII, and Pn as well as Pn and leaf area in both salt-tolerant and salt-sensitive genotypes were found. Saline acidic and saline alkaline soils may play a key role affecting vegetative growth prior to the reproductive stage in rice plants.

Effects of nitrogen application rate and hill density on rice yield and nitrogen utilization in sodic saline–alkaline paddy fields

Soil salinity and alkalinity can inhibit crop growth and reduce yield,and this has become a global environmental concern.Combined changes in nitrogen (N) application and hill density can improve rice yields in sodic saline–alkaline paddy fields and protect the environment.We investigated the interactive effects of N application rate and hill density on rice yield and N accumulation,translocation and utilization in two field experiments during 2018 and 2019 in sodic saline–alkaline paddy fields.Five N application rates (0 (control),90,120,150,and 180 kg N ha^(-1) (N0–N4),respectively) and three hill densities(achieved by altering the distance between hills,in rows spaced 30 cm apart:16.5 cm (D1),13.3 cm (D2) and 10 cm (D3))were utilized in a split-plot design with three replicates.Nitrogen application rate and hill density significantly affected grain yield.The mathematical model of quadratic saturated D-optimal design showed that with an N application rate in the range of 0–180 kg N ha^(-1),the highest yield was obtained at 142.61 kg N ha^(-1) which matched with a planting density of 33.3×10^(4) ha^(-1).Higher grain yield was mainly attributed to the increase in panicles m^(–2).Nitrogen application rate and hill density significantly affected N accumulation in the aboveground parts of rice plants and showed a highly significant positive correlation with grain yield at maturity.From full heading to maturity,the average N loss rate of the aboveground parts of rice plants in N4 was 70.21% higher than that of N3.This is one of the reasons why the yield of N4 treatment is lower than that of the N3 treatment.Nitrogen accumulation rates in the aboveground parts under treatment N3 (150 kg N ha^(-1)) were 81.68 and 106.07% higher in 2018 and 2019,respectively,than those in the control.The N translocation and N translocation contribution rates increased with the increase in the N application rate and hill density,whereas N productivity of dry matter and grain first increased and then decreased with the increase in N application rate and hill density.Agronomic N-use efficiency decreased with an increase in N application rate,whereas hill density did not significantly affect it.Nitrogen productivity of dry matter and grain,and agronomic N-use efficiency,were negatively correlated with grain yield.Thus,rice yield in sodic saline–alkaline paddy fields can be improved by combined changes in the N application rate and hill density to promote aboveground N accumulation.Our study provides novel evidence regarding optimal N application rates and hill densities for sodic saline–alkaline rice paddies.

Short-term effects of biochar and gypsum on soil hydraulic properties and sodicity in a saline-alkali soil

Salt and sodicity of saline-alkali soil adversely affect the construction of ecological landscapes and negatively impact crop production.The reclamation potential of biochar(BC,wheat straw biochar applied at\%by weight),gypsum(G,0.4%by weight),and gypsum coupled with biochar(GBC)was examined in this laboratory-based study by evaluating their effects on a saline-alkali soil(silt loam)with no amendment as a control(CK).Saline ice and fresh water(simulated rainfall)were leached through soil columns to investigate changes in salt content,sodium adsorption ratio(SAR),alkalinity,and pH of the leachate and the soil.Results showed that saturated water content and field water capacity(FWC)significantly increased by 4.4%and 5.6%,respectively,in the BC treatment after a short incubation time.Co-application of biochar and gypsum(GBC)increased soil saturated hydraulic conductivity(Ks)by 58.4%,which was also significantly higher than the sole addition.Electrical conductivity(EC)of the leachate decreased sharply after saline ice leaching;subsequent freshwater leaching accelerated the removal of the rest of the salts,irrespective of the amendment application.However,the application of gypsum(G and GB)significantly enhanced the removal of exchangeable Na^+and reduced leachate SAR.After leaching,the soil salt content decreased significantly for all treatments.The application of gypsum resulted in a significantly lower soil pH,exchangeable sodium percentage(ESP),SAR,and alkalinity values than those recorded for the CK and BC treatments.These results demonstrated that the co-application of gypsum and biochar could improve saline-alkali soil hydraulic conductivity and decrease leaching-induced sodicity over a short period.

The applicability of biochar and zero-valent iron for the mitigation of arsenic and cadmium contamination in an alkaline paddy soil

In paddy fields, the opposing transformation of arsenic (As) and cadmium (Cd) poses many challenges for their simultaneous remediation.In our previous study,we reported that combined biochar and zero-valent iron(ZVI)amendment had great potential for the simultaneous alleviation of As and Cd bioavailability in contaminated acid paddy soil.In this study,an As-and Cd-contaminated alkaline paddy soil was further studied,and the same ZVI-biochar mixtures amendments were applied to evaluate the impact of the mixtures on As and Cd transformation and translocation in the soil-rice system by performing pot experiments with rice.In line with our previous study,the ZVI-biochar composites significantly reduced As and Cd accumulation in different rice tissues,leading to a 42%and 47%decrease in rice grain As and Cd levels,respectively,compared with the control values.The ZVI-biochar mixtures exhibited synergistic effects of biochar and ZVI by enhancing the transformation of bioavailable As and Cd fractions into less bioavailable fractions,and by increasing iron plaque formation to reduce As and Cd bioavailability.Although the bioaccumulation and translocation factors of As and Cd in alkaline paddy soil were generally lower than those in acid paddy soil,particularly in the presence of the ZVI-biochar mixtures,the grain As and Cd levels did not achieve the desired food safety standard levels,probably related to the high soil As content and the small changes in soil pH.Nevertheless,for treating lightly and moderately contaminated paddy soils,ZVI-biochar mixtures can still be a good choice in the future.

Effect of Trichoderma viride biofertilizer on ammonia volatilization from an alkaline soil in Northern China

Ammonia（NH3） volatilization is one of the primary pathways of nitrogen（N） loss from soils after chemical fertilizer is applied, especially from the alkaline soils in Northern China, which results in lower efficiency for chemical fertilizers. Therefore, we conducted an incubation experiment using an alkaline soil from Tianjin（p H 8.37–8.43） to evaluate the suppression effect of Trichoderma viride（T. viride） biofertilizer on NH3 volatilization, and compared the differences in microbial community structure among all samples. The results showed that viable T. viride biofertilizer（T） decreased NH3 volatilization by 42.21% compared with conventional fertilizer（（CK）, urea）, while nonviable T. viride biofertilizer（TS） decreased NH3 volatilization by 32.42%. NH3 volatilization was significantly higher in CK and sweet potato starch wastewater（SPSW） treatments during the peak period. T. viride biofertilizer also improved the transfer of ammonium from soil to sweet sorghum. Plant dry weights increased 91.23% and 61.08% for T and TS, respectively, compared to CK. Moreover, T. viride biofertilizer enhanced nitrification by increasing the abundance of ammonium-oxidizing archaea（AOA） and ammonium-oxidizing bacteria（AOB）. The results of high-throughput sequencing indicated that the microbial community structure and composition were significantly changed by the application of T. viride biofertilizer. This study demonstrated the immense potential of T. viride biofertilizer in reducing NH3 volatilization from alkaline soil and simultaneously improving the utilization of fertilizer N by sweet sorghum.

Research on controllable alkaline soil degradation of 5-substituted chlorsulfuron

Sulfonylurea（SU） has become one class of the most important herbicides worldwide due to their ultralow application rate and mammalian toxicity. Recently application licenses of 3 classical SU herbicides chlorsulfuron, metsulfuron-methyl and ethametsulfuron were suspended due to their undesirable long persistence which is incompatible with the particular rotation planting system in China. Our previous study has discovered that electron-donating groups, especially dimethylamino and diethylamino substituents, on the 5 th position of the benzene ring in chlorsulfuron, greatly accelerated its degradation rate in an acidic soil（p H 5.41）. Owing to the natural slower degradation of SUs in alkaline soil,dimethylamino and diethylamino substituted chlorsulfuron Ia and Ib were further studied in an alkaline soil（p H 8.46） with chlorsulfuron as a control. The experimental data indicated that the half-life of degradation（DT50） of Ia was 3.36 days while Ib was 6.25 days which amounted to 30 and 15 folds faster than chlorsulfuron（DT5084.53 days）, respectively. The research confirmed that our newly-designed structures Ia and Ib can hasten their degradation rate in alkaline soil as well as in acidic soil. This structural modification of the classical SU provided an opportunity to control the degradation rate to reduce their impact on relevant environment and ecology.

Moderate sewage sludge biochar application on alkaline soil for corn growth:a field study

In view of the risks induced by the inhibitory effects of applying impracticably large amounts of sewage sludge biochar(SSB)to the alkaline soil,this field study investigated the influence of moderate biochar amendments(0,1500,4500,and 9000 kg/hm2)on corn growth,alkaline soil properties,and the uptake of potentially toxic elements(PTEs).The results showed that applying more SSB would decrease the ammonium nitrogen concentration and increase the available phosphorus and potassium concentrations,which inhibited corn plant growth because of high background nutrient levels of the alkaline soil.When the alkaline soil was amended with 1500 kg/hm2 SSB,the dry weight of 100 niblets increased from 32.11 g in the control to 35.07 g.There was no significant variation in the total concentration of PTEs in the soil.The concentrations of Mn,Ni,Cu,and Zn in niblets decreased from 5.54,0.83,2.26,and 27.15 mg/kg in the control to 4.47,0.62,1.30,and 23.45 mg/kg,respectively.Accordingly,the health risk from corn consumption was significantly reduced.Furthermore,the combination of SSB and fertilizer improved corn growth and reduced the risk of consumption of PTEs.Therefore,considering the increase in corn fruit yield and the decrease in consumption risk,applying 1500 kg/hm2 of biochar to alkaline soils is a realistically achievable rate,which can broaden the utilization of SSB for remediation of different types of soil.