Forest Soil Cation Dynamics and Increases in Carbon on the Allegheny Plateau, PA, USA Following a Period of Strongly Declining Acid Deposition

Reductions in exchangeable calcium and magnesium and increase in exchangeable aluminum concentrations have been shown in soils impacted by acid deposition, including at four sites on the Allegheny Plateau, PA, USA, sampled in 1967 and 1997 during a period of peak deposition. We repeated sampling at these sites in 2017 to evaluate changes in soils during the more recent period when there has been a strong decline in acid deposition. The uppermost horizons, including the Oa and A horizons where humified organic matter transitions to mineral soil, were thicker, had higher concentrations of organic carbon and exchangeable calcium and magnesium, and lower concentrations of exchangeable aluminum in 2017 compared to 1997, approximating values measured in 1967. Below the Oa/A horizons, 2017 soil chemistry was more similar to the 1997 results, with some reduction of Ca in the recent measurements. These results suggest recovery of base cation–aluminum balance in surface horizons and may indicate a reduction of aluminum mobilization and increased efficiency of vegetation recycling of nutrients with decreased acid anion concentrations. These changes are consistent with a partial recovery from acid deposition. However, the increase in humified soil organic matter may also be affected by coincident increases in temperature and soil moisture.

Responses of crop yield, apparent potassium balance, and soil potassium status to long-term fertilization and lime addition in acidic Ultisol

Soil acidification is one of the major soil degradation phenomenon in tropical and subtropical region, which cause reductions in soil fertility, particularly potassium (K), and declines in crop yield. However, it remains unclear whether and how the status of K in soils and crops changes with the application of lime to alleviate soil acidification. Six treatments of long-term experiments (started 1990) in subtropical region were carried out. Regardless of fertilization regime, lime addition markedly increased grain and straw yields compared to those yields without lime application. Lime addition also led to significant decreases in the apparent K balances compared to soils without lime application. The agronomic K efficiency and partial factor productivity of K fertilizer both significantly increased after lime application. Lime addition reduced the soil exchangeable K (EK) content and stock, while increased soil non-exchangeable K (NEK) content and stock. Redundancy analysis showed that K input, lime, pH, and exchangeable calcium all significantly affected the K in soil and crops. Path analysis showed that lime indirectly influenced soil K (EK and NEK) by directly affecting soil pH, exchangeable calcium, K uptake and apparent K balances. These results suggest that lime addition is a viable strategy for improving crop yields and K fertilizer efficiency in degraded soils caused by acidification. Lime significant increased K uptake which lead to decreased soil EK content and stock. Additional, lime also increased soil NEK content and stock which was regulated by soil pH, exchangeable calcium, and crop growth.

Influence of irrigated mineralized waters on properties of ordinary chernozem in the conditions of Prysamaria Dniprovske

Irrigation of lands in arid climates helps to solve the problem of water deficit of soils in order to increase their fertility. However, under the influence of mineralized waters used for irrigation, there is a degradation of chemical, physico-chemical, water-physical and physical properties of soils. Soil monitoring is one of the effective mechanisms that allowsassessing the current state of soils and predicting the negative consequences of economic activity in the future. The area where the research was conducted is in the zone of insufficient moisture where there is an annual deficit of water balance of soils. Irrigation in the studied areas began in the mid-70s of the last century and lasted until 1992. The waters of the Samara River were used for this purpose. The total mineralization of water during the growing season reaches 3515 mg/dm3. It is possible to estimate the degree of transformation of soils that have been under the influence of irrigation waters for a long time in relation to the indicators of virgin soils. The zonal soils of the research area are CalcicChernozems. The analysis of macromorphological indicators showed that irrigation soils differ from the reference ones by the thickness of the organogenic horizon, density and structure. The results of the analysis of the aqueous extract of the reference soils show the absence of salinization with water-soluble salts. Their content varies in the range from 0.051 to 0.078 %. A maximum of one salt is observed in the soil profile, namely in the transitional horizon at a depth of 45–63 cm. Below this depth, the content of water-soluble salts progressively decreases. The total content and distribution of water-soluble salts in the soil profile of irrigated soils has some differences from the reference soils. In the upper part of the humus horizon, the total amount of water-soluble salts is smaller, which can be attributed to the effects of machining and better aeration, as well as the intensive removal of their vegetation. Below these horizons, the amount of water-soluble salts progressively increases and reaches a maximum in the soil-forming rock. The nature of the distribution in the soil profile and the total amount of salts isnot typical for Calcic Chernozems and ismore similar to those of Gleyic Calcic Chernozems. The maximum amount of water-soluble salts is concentrated in the parent rock. Their percentage indicates the absence of salinity in both studied soils. But guided by the method of calculating the content of toxic water-soluble salts in the soil, in the reference soils, this figure reaches 0.21 t/ha in a meter layer of soil, and in irrigation 0.42 t/ha. The results of studies of physicochemical parameters show that a higher content of metabolic calcium is characteristic of the reference soils, and its distribution in the soils along the profile of both options is relatively similar. In contrast, the distribution of exchangeable magnesium in the soil profile varies greatly, especially in the reference soils. In irrigated soils, the ratio of exchangeable calcium to magnesium is more stable and varies in the range from 4.2 to 7.9, which may be the result of prolonged irrigation. According to the obtained physicochemical parameters, irrigation soils have weak salinity in the lower part of the transition horizon. This indicator, together with the ratio of exchangeable calcium to magnesium, indicates eluvial-illuvial processes that for some time contributed to the redistribution in the soil profile of both water-soluble salts and exchangeable cations. Evaluation of the degree of salinity of soils showed the absence of salinization in the reference soils, as well as in the upper part of the humus horizons of irrigated soils. Given the buffering of irrigated soils, weak salinity is present only in the upper part of the transition horizon.

Correlation of Physico-chemical Characteristic with Available Nutrients and Leaf Nutrient Content in Apple (Cv. Red Delicious) Orchard of Jammu and Kashmir (India)

To study the “Nutrient Status of Apple Orchard Soils of South Kashmir” a survey was carried in twenty apple orchards (cv. Red Delicious) of south Kashmir. The soil samples were analyzed for studying the Correlation between physico-chemical characteristic and available nutrients. The correlation coefficient studies revealed that pH indicated significant and positive correlation coefficient with exchangeable calcium and magnesium and exhibited significant and negative relationship with available nitrogen, phosphorus, potassium, sulphur, iron, manganese, zinc and copper. The organic carbon showed positive and significant correlation coefficient with available nitrogen, phosphorus, sulphur, iron, zinc and copper. The calcium carbonate showed significant and positive correlation with exchangeable calcium and magnesium but significant and negative correlation coefficient with available nitrogen, phosphorus, potassium, iron, manganese and zinc. The clay content revealed significant and positive relationship with available potassium only. The leaf analysis showed that apple orchards were adequate in all nutrients, whileas, nitrogen was marginal to high and phosphorus was marginal to adequate.

Evaluating digital soil mapping approaches to predict topsoil exchangeable calcium and magnesium in a sugarcane field of Australia

<p><strong>Evaluating digital soil mapping approaches to predict topsoil exchangeable calcium and magnesium in a sugarcane field of Australia</strong></p><p>Maryem Arshad<sup>1</sup>, Dongxue Zhao<sup>1</sup>, Tibet Khongnawang<sup>1</sup> and John Triantafilis<sup>1*</sup></p><p><sup>1</sup>School of Biological, Earth and Environmental Sciences, Faculty of Science, UNSW Sydney, Kensington, NSW, 2052, Australia</p><p><strong>Corresponding </strong></p><p>John Triantafilis, School of Biological, Earth and Environmental Sciences, Faculty of Science, UNSW Sydney, Kensington, NSW, 2052, Australia</p><p>Email: [email protected]</p><p><strong>Abstract</strong></p><p>Knowledge about spatial distribution of exchangeable (exch.) calcium (Ca) and magnesium (Mg) is needed to maintain sugarcane biomass in north Queensland, Australia. To create digital soil maps (DSM), herein, we evaluated three approaches, including; geostatistical (i.e. ordinary kriging [OK]), statistical and hybrid. We first determined the number of samples (10 – 120) required to compute variogram by calculating nugget to sill ratio (NSR) and sum of squared error (SSE). We then used this variogram with OK to predict topsoil (0 – 0.3 m) exch. Ca and Mg. For comparison, four statistical models, including; one linear regression (LR) and three machine learning (ML) models (i.e. Cubist, support vector machine [SVM] and random forest [RF]) were used. Doing so, usefulness of two digital data, including; gamma-ray (g-ray) and soil apparent electrical conductivity (EC<sub>a</sub>), either individual or combined, was tested. Regression residuals (RR) were then added to find out improvement in prediction performance (i.e. Lin’s) and in hybrid approach. Influence of varying sample size (10 – 120) was also determined on all three DSM approaches. Comparisons were then drawn with a traditional soil type map and by calculating the mean square prediction error (MSPE). Finally, Digital soil maps (DSM) of exch. Ca and Mg were developed. Results showed that 50 samples were enough to compute a good variogram for exch. Ca (NSR = 11%, SSE = 0.39) and Mg (NSR = 33%, SSE = 0.005). Considering OK, exch. Ca and Mg were predicted with moderate agreement (Lin’s = 0.65 – 0.80). Comparing statistical models and to predict exch. Ca, RF (0.64) and SVM (0.63) outperformed Cubist and LR (0.60) while to predict exch. Mg, SVM (0.79), RF and Cubist (0.74) outperformed LR (0.62). Combined and individual g-ray data performed best and equally well. Hybrid models i.e. RK and CubistRR improved prediction of exch. Ca (0.76) and Mg (0.81) using individual g-ray and EC<sub>a</sub> data, respectively. Considering sample size, OK and statistical models required 80 samples while hybrid models required only 30 samples to satisfactorily (Lin’s ≥ 0.70) predict exch. Ca and Mg. Comparisons based on MSPE showed that to predict exch. Ca, hybrid (RK = 1.44) was the best approach followed by geostatistical (OK = 1.94), statistical (Cubist = 2.15) and then traditional soil map (2.64). Same was the case for exch. Mg. DSM of predicted exch. Ca and Mg were consistent with contour plots of measured data. However, some poor predictions were apparent across field edges or areas where small scale variation in digital or soil data was prevalent.  </p>

Soil and Leaf Nutritional Studies and Status of Healthy and Declined Mandarin Orchards

The present investigation was carried out to determine soil and leaf nutritional status of some typical healthy and declined mandarin orchards of Amravati District (M.S) during 2016-19.Total twenty five representative surface and depth wise soil and leaf samples from healthy and declined mandarin orchards were collected and analyzed various nutrients in plant as well as leaf samples. The data analysis showed that total nitrogen content in healthy and declined mandarin orchards from surface soils varied from 0.045 to 0.093 % and 0.015 to 0.37% respectively. The available nitrogen, phosphorus and potassium content of healthy orchards surface soils varied from 200.0 to 265.7 kg ha-1 , 22.0 to 35.3 kg ha-1 , 320.0 to 665.0 kg ha-1 and in declined orchards it varied from 130.4 to 203.5 kg ha-1 , 17.8 to 21.3 kg ha-1 , 360.0 to 744.4 kg ha-1 respectively. The exchangeable calcium and magnesium together constitute more than 80% of exchange complex. The exchangeable calcium, magnesium and sulphur content in healthy orchards surface soils varied from 26.34 to 30.22 cmol (p+ ) kg ha-1 , 11.71 to 16.92 cmol (p+ ) kg ha-1 , 0.27 to 0.90 kg ha-1 and in declined orchards it varied from 29.00 to 31.98 cmol (p+ ) kg ha-1 , 12.07 to 13.71 cmol (p+ ) kg ha-1 , 0.36 to 0.69 kg ha-1 respectively. Micronutrients status of orange orchards showed that available copper, zinc, iron and manganese in healthy orchards surface soils varied from 2.20 to 5.60 ppm, 0.50 to 0.79 ppm, 4.50 to 6.29 ppm, 12.61 to 18.11 ppm and in declined orchards it varied from 1.90 to 2.48 ppm, 0.35 to 0.46 ppm, 3.40 to 5.00 ppm, 8.10 to 12.24 ppm respectively. Findings revealed that total nitrogen, available nitrogen, phosphorus, sulphur, zinc and manganese content found more supporting in healthy orchards than declined ones. Depth wise distribution showed that total nitrogen, available nitrogen, phosphorus and copper showed decreasing trend with the soil depth. The leaf nutrient content in the plant showed that nitrogen, phosphorus and potassium content in leaf of healthy orchards varied from 2.35 to 2.55%, 0.14 to 0.17%, 0.82 to 1.00% and in declined orchards it varied from 1.75 to 2.00%, 0.10 to 0.13%, and 0.84 to 1.70% respectively. Calcium, magnesium and sulphur content in healthy orchards varied from 3.00 to 3.90%, 0.60 to 0.74%, 0.21 to 0.19% and in declined orchards it ranged from 2.40 to 3.15%, 0.33 to 0.74%, and 0.19 to 0.23% respectively. Results pertaining to micronutrient showed that iron; manganese, copper and zinc in healthy orchards varied from 105.6 to 140.6 ppm, 21.72 to 34.62 ppm, 29.40 to 35.96 ppm, 30.45 to 39.18 ppm, and in declined orchards it varied from 70.66 to 100.00 ppm, 20.38 to 27.67 ppm, 21.72 to 26.05 ppm, and 17.24 to 25.00 ppm respectively. Results showed that a healthy orchard has significantly higher content of nutrient than declined orchards except potassium content