Using soil organic matter fractions as indicators of soil physical quality

The objective of this study was to evaluate the use of chemical and physical fractions of soil organic matter (SOM), rather than SOM per se, as indicators of soil physical quality (SPQ) based on their effect on aggregate stability (AS). Chemically extracted humic and fulvic acids (HA and FA) were used as chemical fractions, and heavy and light fractions (HF and LF) obtained by density separation as physical fractions. The analyses were conducted on medium-textured soils from tropical and temperate regions under cropland and pasture. Results show that soil organic carbon (SOC), SOM fractions and AS appear to be affected by land use regardless of the origin of the soils. A general separation of structurally stable and unstable soils between samples of large and small SOC content, respectively, was observed. SOM fractions did not show a better relationship with AS than SOC per se. In both geographical regions, soils under cropland showed the smallest content of SOC, HA and carbon concentration in LF and HF, and the largest HF/LF ratio (proportion of the HF and LF in percent by mass of bulk soil). With significant associations between AS and SOC content (0.79**), FA/SOC (r = -0.83**), HA/FA (r = 0.58**), carbon concentration of LF (r = 0.69**) and HF (r = 0.70**) and HF/LF ratio (r = 0.80**), cropland showed lowest AS. These associations indicate that SOM fractions provide information about differences in SOM quality in relation to AS and SPQ of soils from tropical and temperate regions under cropland and pasture

Oversampling by genetic algorithm and k-nearest neighbors for network intrusion problem

A class imbalance problem is a problem in which the number of majority class and minority class varies greatly. In this article, we propose an oversampling method using GA and k-Nearest Neighbors (kNN) to deal with a network intrusion, a class imbalance problem. We use GA as the main algorithm and use a kNN as its fitness function. We compare the proposed method with a very popular oversampling technique which is a SMOTE family. The experimental results show that the proposed method provides better Accuracy, Precision, and F-measure values than a SMOTE family in almost all datasets with almost all classifiers. Moreover, in some datasets with some classifiers, the proposed method also gives a better Recall value than a SMOTE family as well. This is because the proposed method can generate new intruders in a more independent area than a SMOTE family.</jats:p

Effect of Rice Straw on Potassium Availability in Illite Containing Soils of Central Plain, Thailand

Soil potassium (K) in various forms and the effect of rice straw on soil K release were studied in lowland soils containing illite clay minerals. Surface soils of 2 Inceptisols and 2 Alfisols were collected to study. Soil samples were incubated for 120 days with rice straw incorporation at different rates (0, 3,125, 6,250, and 9,375 kg/ha), and various forms of K in soils were determined at various times during the period of incubation. The results showed that the readily available K content (water-soluble K + exchangeable K) of the studied soils increased with the increasing rate of rice straw incorporation. In addition, non-exchangeable K content also increased with the increasing rate of rice straw incorporation by fixation process for all soils. The maximum increase of water-soluble K content of the studied soils was observed on the 4th day of incubation for all treatments, corresponding to the decrease of exchangeable K content at the same time. This result indicated that water-soluble K and exchangeable K were in equilibrium. Changes of non-exchangeable K content during the period of incubation through alternate release and fixation processes were observed monthly. This result suggested that most of the readily available K enhanced by rice straw incorporation would be beneficial for K uptake by the plant.</jats:p

Cassava Response to Phosphorus Fertilizer in Warin Soil Series Amended with Cassava Tails and Stalk-Bentonite Mixture

A field experiment was conducted in a farmer field in Nakhon Ratchasima province, northeast, Thailand objectively to investigate the response of cassava, Huay Bong 80 variety to phosphorus (P) fertilizer in Warin soil series (classified as Grossarenic Paleustults) amended with cassava tails and stalk (CTS) mixed with bentonite (BTN).  The experiment was arranged in split plot with four replications.  Main plot consisted of four rates of CTS +BTN: 0+0, 6.25+1.25, 12.5+2.5 and 25+5 t/ha while subplot comprising four rates of P fertilizer: 0, 25, 50 and 100 kg P2O5/ha.  Cassava was harvested at 12-month of age and plant samples were collected at the harvesting time to study the effects of soil amendment on the uptake of primary plant nutrients in different plant parts of cassava.  The results showed that the CTS+BN mixture at the rate of 25+5 t/ha highly significantly promoted the highest fresh tuber yield (FTY) and starch yield (SY) of 31.79 and 8.97 t/ha, respectively, which were 21.2 and 20.7 % greater than that of the control with no soil amendment addition. Increasing rate of P fertilization highly significantly induced greater FTY, SY and aboveground biomass (ABG) than did the zero-P fertilization. Amending the soil with 25+5 t/ha of CTS+BN along with the addition of 100 kg P2O5/ha interactively gave the significantly highest respective FTY, SY and ABG of 39.76, 11.48 and 17.35 t/ha whereas the plot amended with 12.5+2.5 kg CTS+BN/ha plus 50 kg P2O5/ha fertilization gave slightly lower STY and SY of 36.11 and 10.30 t/ha, respectively.  The former combined rate of soil amendment and P fertilizer also had the interaction that highly significantly induced the highest uptake of all primary plant nutrients in the whole plant, accounting for 131.66, 14.23 and 124.13 kg/ha of respective nitrogen, phosphorus, and potassium.  The result reaffirmed that amending the soil with proper rate of CTS+BTN mixture enhanced the efficiency of P fertilizer and subsequently improved yield of cassava. HIGHLIGHTS Coarse-textured soils in northeast Thailand are very poor physically and chemically, leading to low yield of cassava planted Improving the soils with proper soil amendments combined with phosphorus fertilization can be beneficial to an increase of cassava yield Amending Warin soil series, one of the coarse-textured soils in this region, with 25+5 t/ha of cassava tails and stalk + bentonite along with the addition of 100 kg P2O5/ha interactively gave the significantly highest fresh tuber yield, starch yield and aboveground biomass of cassava GRAPHICAL ABSTRACT</jats:p