Tillage and drainage impact on soil quality: II. Tensile strength of aggregates, moisture retention and water infiltration

Tillage-induced changes in soil quality are important to understanding soil strength and water retention and transmission properties. Thus, this study was conducted to assess the effects of two tillage systems under un-drained and drained conditions on tensile strength (TS) of 5–8 mm aggregates, soil water characteristics (SWC), plant available water (PAW), and the water infiltration rate (i). Soil properties were determined mainly in the surface (0–10 cm) layer on a Crosby (fine, mixed, mesic, Aeric Ochraqualf) silt loam soil at the Waterman Farm of the Ohio State University, Columbus, OH on a 14-year-old field study. Effect of two tillage treatments comprising no-tillage (NT) and conventional tillage (CT) were studied for two levels of drainage: un-drained (UD) and tile drained (D). The TS for 0–10 cm depth was significantly (P ≤ 0.01) affected by tillage and drainage treatments, and was higher in CT than NT by 61% in UD and by 48% in D soil. In comparison, TS increased by 13% in NT and 4% in CT in D compared with the UD treatments. Soil organic carbon (SOC) in 0–10 cm depth of NT–UD treatment was 23% higher than CT–UD treatment and 38% more than NT–D treatments. Tillage and drainage impact on SWC was non-significant at 0 kPa suction, but significant (P ≤ 0.1) at −3, −6, −10, −30, −100 and −300 kPa suctions indicating that water was retained more in NT–UD than CT–UD soil. The PAW was significantly influenced by drainage (P ≤ 0.01) but not by tillage treatments. Yet, there existed a general trend of about 8% more PAW in NT–UD than CT–UD treatments. In contrast, PAW was 48% more in soil from NT–UD than NT–D treatments. PAW increased with increase in the SOC concentration (R² = 0.89; P ≤ 0.01). There were also differences in soil water sorptivity (S), and equilibrium infiltration rate (i_c) in NT–UD compared with CT–UD treatments. A positive and significant correlation (r = 0.57, P ≤ 0.05) occurred between i_c and SOC concentration. The value of S was more in NT–UD by 70% than CT–UD, and 46% in NT–D than CT–D. Similarly, the i_c was more in NT than CT by 119% in UD compared with 82% in D soil. The value of A in NT was higher than that in CT by 39% and 12% in UD and D treatments, respectively. The mean cumulative infiltration (I) in 3 h was 71.4 cm in NT versus 44.0 cm in CT in UD compared with 62.1 cm in NT and 48.4 cm in CT for the D treatment. The I was positively and significantly correlated with SOC concentration (r = 0.32, n = 12, P ≤ 0.1) indicating improvement of I with increase in SOC concentration. Results of this study suggest that conversion from CT to NT management system may reduce the risk of surface runoff, increase soil aggregation, and improve soil hydrological properties.     

Relationships among different geographical groups,agro-morphology,fatty acid composition and RAPD marker diversity in Safflower (<Emphasis Type="Italic">Carthamus tinctorius</Emphasis>)

Patterns of geographical diversity, and the relationship between agro-morphological traits and fatty acid composition were assessed for 193 safflower (Carthamus tinctorius) accessions representing forty countries. Accessions were assigned to eight groups based on geographical proximity. Cluster and Principal Component analyses were performed to assess patterns of diversity among the accessions and to select the most distant accessions from each of eight groups for analysis of randomly amplified polymorphic DNA (RAPD) markers. There was a large amount of diversity for agro-morphological traits, fatty acid composition, and RAPD markers. Most correlations among different traits were rather low. Plant height showed a positive correlation with days to flowering (r = 0.63**). Palmitic acid was positively correlated with stearic acid and oleic acid values, and negatively correlated with linoleic acid (P < 0.01). Oleic acid and linoleic acid showed a strong negative correlation (r = −0.89**). The first three principal components together explained 59% of the variation, however, neither principal component analysis (PCA) nor marker analysis revealed a clear relationship between diversity pattern and geographical origin. Accessions from some geographical regions tended to group together, such as accessions from South Western Asia, Central Western Europe, and the Mediterranean region. The correlation between the morphological matrix and the genetic matrix based on RAPD markers was not significant (r = 0.027). Wide diversity in safflower germplasm indicates a considerable potential for improving this crop for both agronomic and quality traits.     

Role of site in the mortality and production of Acacia mangium plantations in Indonesia

In Indonesia, Acacia mangium plantations exceed 1.6 Mha contributing approximately 3.5% of the country’s GDP. The viability of these plantations is increasingly threatened by fungal pathogens, insect pests, squirrels, monkeys, elephants and wind damage. Studies indicate that the problem is growing and in some areas, fungal pathogens such as Ganoderma and Ceratocystis species have contributed up to 50% tree mortality by the fourth rotation. Multiple statistical procedures were employed to examine the influence of soil and topographical properties on tree survival (trees ha^?1), wood production (m³ ha^?1), and mortality associated with Ganoderma root rot, Ceratocystis wilt and by wind. Soil family level was found to be a good indicator of tree mortality. Plots with fine-loamy Typic Kandiudult soils had the highest tree survival and mortality associated with species of Ganoderma and Ceratocystis, but had the lowest incidence of mortality by wind. The degree of association between soil and topographic variables with tree survival, wood production and the cause of mortality were poor and inconsistent. Tree survival was slightly higher on upslope areas away from valley bottoms, and drier mid-slopes, ridges and hilltops, and very low pH (<3.3) soils. Wood production was also slightly higher in drier, elevated locations, away from valley bottoms. Mortality by wind was slightly higher in moist, poorly drained, low-lying valley bottoms and topographically flat areas. Our ability to further pinpoint the influence of topography and soil attributes on wood production and cause of mortality was greatly compromised by the lack of site-specific soil data, and potential misclassification of the cause of mortality. This study could not reliably or consistently relate tree survival, wood production or the cause of mortality to any one, or combination of, soil and topographic variables.     

Inheritance pattern of mungbean yellow mosaic disease resistance and gene action for different traits in mungbean (Vigna radiata (L.) Wilczek) under protected and unprotected field conditions

Understanding of mungbean yellow mosaic disease resistance is crucial to develop resistant varieties to combat worldwide threat of the disease epidemics. This study was aimed to determine nature of disease resistance in terms of number of genes governing it and genetics of related traits. Experimental site was located on 31.43°N and 73.06°E with an elevation of 186 m, and evaluation trials were conducted during spring season due to high disease epidemics in this season. Two contrasting genotypes, that is, NM 6‐68‐2 (resistant) and NM 1‐32‐1 (highly susceptible), were crossed to raise six populations, that is, P₁, P₂, F₁, F₂, BC₁ and BC₂ for evaluation under protected and unprotected field conditions using chi‐square test and generation mean and variance analysis. It was discovered that disease resistance was governed by two major genes with additive effects. Disease resistance can easily be incorporated through backcrossing and direct selection following hybridization. Direct selection should be practised at earlier generation for plant height, chlorophyll contents and number of seeds per pod due to preponderance of additive effects whereas at later generations for seed yield per plant, 100 seed weight, harvest index, number of pods per plant and pod length due to involvement of duplicate epistasis.     

Changes in Availability of Plant Nutrients during Composting of Cow Manure with Poplar Leaf Litter

Safe management of animal and plant waste is one of the world's most important environmental challenges. Composting has been proposed as a useful technique for beneficially recycling wastes. This study showed that significant temporal changes in the nutrient availability occurred during the composting of cow manure with poplar leaf litter within 120 days. In particular, total C in the final compost was directly related to the addition of tree litter and inversely related to the time of composting, whereas extractable P and NO₃ increased with increasing amounts of tree litter and ammonium showed the opposite trend. During the later stages of the composting process higher concentrations of water soluble K, Ca, Mg, and Na were observed. The major benefit observed was that heavy metal concentrations initially present in the manure were significantly reduced during composting. Heavy metals in the final compost decreased in the order: Fe > Mn > Zn > Cu > Ni > Cd. The increased availability of plant nutrients following composting coupled with the lower extractability of heavy metals indicates that composting may be a sustainable option for agricultural waste recycling and increased productivity.     

Biochar for crop production: potential benefits and risks

Purpose

Biochar, the by-product of thermal decomposition of organic materials in an oxygen-limited environment, is increasingly being investigated due to its potential benefits for soil health, crop yield, carbon (C) sequestration, and greenhouse gas (GHG) mitigation.

Materials and methods

In this review, we discuss the potential role of biochar for improving crop yields and decreasing the emission of greenhouse gases, along with the potential risks involved with biochar application and strategies to avoid these risks.

Results and discussion

Biochar soil amendment improves crop productivity mainly by increasing nutrient use efficiency and water holding capacity. However, improvements to crop production are often recorded in highly degraded and nutrient-poor soils, while its application to fertile and healthy soils does not always increase crop yield. Since biochars are produced from a variety of feedstocks, certain contaminants can be present. Heavy metals in biochar may affect plant growth as well as rhizosphere microbial and faunal communities and functions. Biochar manufacturers should get certification that their products meet International Biochar Initiative (IBI) quality standards (basic utility properties, toxicant assessment, advanced analysis, and soil enhancement properties).

Conclusions

The long-term effects of biochar on soil functions and its fate in different soil types require immediate attention. Biochar may change the soil biological community composition and abundance and retain the pesticides applied. As a consequence, weed control in biochar-amended soils may be difficult as preemergence herbicides may become less effective.

     

Phosphorus-Mobilizing Rhizobacterial Strain Bacillus cereus GS6 Improves Symbiotic Efficiency of Soybean on an Aridisol Amended with Phosphorus-Enriched Compost

Legume plants are an essential component of sustainable farming systems. Phosphorus (P) deficiency is a significant constraint for legume production, especially in nutrient-poor soils of arid and semi-arid regions. In the present study, we conducted a pot experiment to evaluate the effects of a phosphorus-mobilizing plant-growth promoting rhizobacterial strain Bacillus cereus GS6, either alone or combined with phosphate-enriched compost (PEC) on the symbiotic (nodulation-N₂ fixation) performance of soybean (Glycine max (L.) Merr.) on an Aridisol. The PEC was produced by composting food waste with addition of single super phosphate. The bacterial strain B. cereus GS6 showed considerable potential for P solubilization and mobilization by releasing carboxylates in insoluble P (rock phosphate)-enriched medium. Inoculation of B. cereus GS6 in combination with PEC application significantly improved nodulation and nodule N₂ fixation efficiency. Compared to the control (without B. cereus GS6 and PEC), the combined application of B. cereus GS6 with PEC resulted in significantly higher accumulation of nitrogen (N), P, and potassium (K) in grain, shoot, and nodule. The N:P and P:K ratios in nodules were significantly altered by the application of PEC and B. cereus GS6, which reflected the important roles of P and K in symbiotic performance of soybean. The combined application of PEC and B. cereus GS6 also significantly increased the soil dehydrogenase and phosphomonoesterase activities, as well as the soil available N, P, and K contents. Significant positive relationships were found between soil organic carbon (C) content, dehydrogenase and phosphomonoesterase activities, and available N, P, and K contents. This study suggests that inoculation of P-mobilizing rhizobacteria, such as B. cereus GS6, in combination with PEC application might enhance legume productivity by improving nodulation and nodule N₂ fixation efficiency.     

Effect of Oil Palm Fly Ash on Soil Properties and Yield of Sweet Corn in the Tropical Zone of Thailand

Disposal of oil palm fly ash (OPFA) into the environment causes environmental pollution. A field experiment was conducted to evaluate the effects of OPFA and mineral fertilizer on soil properties and yield of sweet corn. A total of six treatments were applied that included 2, 4, and 6 t ha^–1 OPFA, 200 kg ha^–1 nitrogen, phosphorus, and potassium (NPK), 100 kg ha^–1 NPK + 2 t ha^–1 OPFA as well as the control. A significant increase in soil pH and available P was observed with the sole OPFA treatments at 2, 4, and 6 t ha^–1, while a significant increase in exchangeable cations [K, magnesium (Mg)] was detected only at the 6-t ha^–1 OPFA treatment. The highest grain yield of 4220 kg ha^–1 was obtained at the 100-kg ha^–1 NPK + 2 t ha^–1 OPFA-treated plots, which was statistically similar with the grain yield of 3800 kg ha^–1 received at the 200-kg ha^–1 NPK-treated plots. The practical implication of this study is that OPFA can be used as a liming material to increase soil pH and it has a synergetic effect in combination with inorganic fertilizer.     

Impact of Various Ratios of Nitrogen and Sulfur on Maize and Soil pH in Semiarid Region

Nitrogen and sulfur play an important role in maize production. The aim of this study was to evaluate the effect of nitrogen (N) and sulfur (S) levels applied in various ratios on maize hybrid Babar yield at Peshawar in 2011 and 2013. Four N levels (120, 160, 200 and 240 kg N ha^?1) and four S levels (20, 25, 30 and 35 kg S ha^?1) were applied in three splits: a, at sowing; b, V8 stage; c, VT stage in ratios of 10:50:40, 20:50:30 and 30:50:20. Grains ear^?1, thousand grain weight, grain yield ha^?1 and soil pH were significantly affected by years (Y), N, S and their ratios, while no effect of N, S and their ratios was noted on ears plant^?1. Maximum grains ear^?1 (390), thousand grain weight (230.1 g) and grain yield (4119 kg ha^?1) were recorded in 2013. N increased grains ear^?1 (438), thousand grain weight (252 g) and grain yield (5001 kg ha^?1) up to 200 kg N ha^?1. Each increment of S increased grains ear^?1 and other parameters up to 35 kg S ha^?1, producing maximum grains ear^?1 (430), thousand grain weight (245 g) and grain yield (4752 kg ha^?1), while soil pH decreased from 8.06 to 7.95 with the application of 35 kg S ha^?1. In the case of N and S ratios, more grains ear^?1 (432), heavier thousand grains (246.7 g) and higher grain yield (4806 kg ha^?1) were observed at 30:50:20 where 30% of N and S were applied at sowing, 50% at V8 and 20% at VT stage. It is concluded that 200 kg N ha^?1 and 35 kg S ha^?1 applied in the ratio of 30% at sowing, 50% at V8 and 20% at VT stage is recommended for obtaining a higher yield of maize hybrid Babar.     

Promoting Growth,Yield, and Phosphorus-Use Efficiency of Crops in Maize–Wheat Cropping System by Using Polymer-Coated Diammonium Phosphate

Field experiments were conducted at Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan, to check the effect of polymer-coated diammonium phosphate (DAP) on maize–wheat cropping system. Different rates of polymer-coated and uncoated phosphorus (P) were applied first to maize then followed by wheat after harvesting of maize on same field. Results showed that application of 100% of recommended P from polymer-coated DAP increased plant height (10%), chlorophyll content (4%), biological yield (17%), grain yield (36%), agronomic efficiency (43%), and nitrogen, phosphorus, and potassium contents of maize produces, while in case of wheat 75% recommended P from polymer-coated DAP increased plant height (6%), chlorophyll content (18%), biological yield (20%), grain yield (14%), agronomic efficiency (72%), and nitrogen, phosphorus, and potassium contents of grains and straw as compared with uncoated DAP. So, it can be summarized that polymer-coated DAP can effectively improve growth, yield, and phosphorus-use efficiency of maize and wheat crop.