Hard Pan Research Articles

Substrate heterogeneities cause root growth trajectories to switch from vertical to oblique.

Hard pans, soil compaction, soil aggregation and stones create physical barriers that can affect the development of a root system. Roots are known to exploit paths of least resistance to avoid such obstacles, but the mechanism through which this is achieved is not well understood. Here, we combined 3D-printed substrates with a high-throughput live imaging platform to study the responses of plant roots to a range of physical barriers. Using image analysis algorithms, we determined the properties of growth trajectories and identified how the presence of rigid circular obstacles affects the ability of a primary root to maintain its vertical trajectory. Results showed the types of growth responses were limited, both vertical and oblique trajectories were found to be stable and influenced by the size of the obstacles. When obstacles were of intermediate sizes, trajectories were unstable and changed in nature through time. We formalised the conditions for root trajectory to change from vertical to oblique, linking the angle at which the root detaches from the obstacle to the root curvature due to gravitropism. Exploitation of paths of least resistance by a root may therefore be constrained by the ability of the root to curve and respond to gravitropic signals.

Is using combined tillage implements the solution?

The fuel consumption, The energy requirement, the time of prepare seedbed, the tractor wheel slippage and the number of passes in the field, all of this factors make farmer choose more efficient method of plowing. Compound tillage is the solve and the method means that two, three or more different plowing tools are work at one time for plowing soil, pulverization, seeding and fertilize, the aid of this way, reduce the drudgery, number and saving time of the field operation. The primary (conventional) and secondary tillage implements are becoming expensive time, fuel and cost, additional, need several passes to prepare seedbed, which increase compaction and damage of the soil and leads to formation the hard pan in the soil due to tractor and machines movement. The farmer size of the field holdings in Iraq is middle or usually small, the way of increase the the width of tools or speed is less useful and effective, therefore, reduce and shorten the number of traffic or passes by use a combination tillage implements consider better solution. Compound tillage saving cost of 44-55%, time of 50-55% and enable the farmers to reduce the number of trips over the field, also, shortage of farm labor. Carrying out the tillage process by compound tillage with two or more equipment to reduce time, fuel consumption and power requirement foe prepare the best seedbed. In this review, various paper researches on combination tillage implement will be discussion.

Fencing with the symptom: a Lacanian reading of Laurence Sterne's sentence structure and punctuation in Tristram Shandy

ABSTRACT This essay considers Laurence Sterne's sentences from a Lacanian point of view. My argument parallels the disordered utterances that drive the narrative of Sterne's novel, The Life and Opinions of Tristram Shandy, Gentleman and the framing of psychoanalysis. Its structure as a swarming address to an enigmatic, shifting listener (the essayistic digressions, evasions, and precisions that aren't precisions) recalls the disordered speech of a patient arriving in analysis with an unmanageable, disordering symptom; in the case of Shandy and Sterne, the ‘vile cough' of tuberculosis. Throughout many free-associative sessions, the patient maps out the undislodgeable hard pan of the symptom. By tuning in to areas of anxiety in discourse, the analysand becomes a kind of ‘artist of the symptom’, reappropriating and converting it from a source of disorder to an ordering principle - a sinthome, in Lacan's punning neologism. What cannot be cured must be enjoyed: this is precisely what the author-narrator dyad of Tristram Shandy manages, converting the narrator's cough into the motor of the novel's grammar, syntax, and punctuation; and making the novel the fencing piste for its author-narrator's duel with a symptom that can't be defeated, its distinctive dash being their shared rapier.

Effects of Root Growth of Deep and Shallow Rooting Rice Cultivars in Compacted Paddy Soils on Subsequent Rice Growth

Rice is often grown as multiple seasons in one year, alternating between flooded and upland systems. A major constraint, introduced from the flooded system, is a plough pan that may decrease rooting depth and productivity of follow-on upland rice. Roots penetrating the plough pan under flooded rice system can leave a legacy of weaker root growth pathways. Deeper rooting rice cultivars could have a bigger impact, but no direct evidence is available. To explore whether a deep rather than a shallow rooting rice cultivar grown in a flooded cropping cycle benefited deeper root growth of follow-on rice in an upland, reduced tillage cropping cycle, a simulated flooded paddy in greenhouse was planted with deep (Black Gora) and shallow (IR64) rooting cultivars and a plant-free control. Artificial plough pans were made in between the topsoil and subsoil to form different treatments with no plough pan (0.35 MPa), soft plough pan (1.03 MPa) and hard plough pan (1.70 MPa). After harvest of this ‘first season’ rice, the soil was drained and undisturbed to simulate zero-tillage upland and planted rice cultivar BRRI Dhan 28. The overall root length density (RLD), root surface area, the numbers of root tips and branching of BRRI Dhan 28 did not vary between plough pan and no plough pan treatments. Compared with the shallow rooting rice genotype, the deep rooting rice genotype as ‘first season’ crop produced 19% greater RLD, 34% greater surface area and 29% more branching of BRRI Dhan 28 in the subsoil. In the topsoil, however, BRRI Dhan 28 had 28% greater RLD, 35% greater surface area and 43% more branching for the shallow rather than deep rooting genotype planted in the ‘first season’. The results suggested that rice cultivar selection for a paddy cycle affects root growth of a follow-on rice crop grown under no-till, with benefits to subsoil access from deep rooting cultivars and topsoil proliferation for shallow rooting cultivars.

The Geotechnical Investigation of Subsoil Materials in a Typical Basement Terrain, Southwestern Nigeria- A Case study

Geotechnical investigation of the subsurface materials of a proposed Primary Health Center (PHC) in Modeke Oyo East Local Government Area (OELGA). of Oyo State has been conducted. The investigation is aimed to determine the suitability of the site for the proposed Bungalow building by assessing the subsoil strata that underlie the area. Three (3) points were tested to depth of 4.75m using a 2.5-ton DCPT equipment, while three (3) trial pits were dug to a depth of 1.5m with the aid of hand auger, and various lab analysis were conducted on selected samples from the trial pits. The result obtained from the DCPT indicates that subsurface is made up of stiff to very stiff sandy lateritic clay underlain by very stiff to hard sandy lateritic clay with hard pans layers. The allowable bearing pressure was observed to increase with depth to 4.75m further confirmed the subsurface lithologies. The Allowable Bearing Pressure (qa) in kN/m2) with a range of values 81 – 256 kN/m2, 54 – 155 kN/m2 and 162 – 338 kN/m2 for DCPT points 1, 2, and 3 respectively, indicate a Safe Bearing Pressure that can support load up to 45 kN/m with factor of safety of 2.5. Sieve analysis results revealed that the soil is well graded with dominant gravel which show a well-drained soil with good strength characteristics. Liquid limits ranged from 26.7% to 43.3%, plastic limits from 15% to 27% and plasticity index from 9.7% to 27.3%, thus indicating low to medium compressibility. The natural moisture contents values range between 4% and 15%, indicating lateritic clay of low to medium plasticity with low moisture content. Based on the above deductions, it can be concluded that, the factor of safety of 2.5 calculated from the allowable bearing pressure from the CPT, low to medium compressibility from Atterberg limits test and moisture content below 15% show that the investigated site is good and could safely support a bungalow building as proposed.

Water seepage and retention in purple soil bunds on sloping farmland in the Three Gorges Reservoir area, China

AbstractSoil bunds are a common land reconstruction practice in the Three Gorges Reservoir area of China, and play a key role in runoff regulation and soil conservation on cultivated hillslopes. This study investigated water movement pathways and retaining effects of soil bunds using water transport trajectory observations inferred from field dye tracing experiments. It was found that water infiltration in the bund was characterised by spatial heterogeneity in three dimensions. The stained area ratio (SAR) of the bund was much lower than that of the adjacent field at all depths. Dye patterns resembled inclined strips in the bund, and lateral seepage occurred mainly on the top of hard pan. SAR, stained path width (SPW) <20 mm, and stained path number (SPN) all decreased with increasing horizontal distance. The SPW <20 mm proportion and SAR both decreased according to a logarithmic function, while the changing trend of SPN followed a first‐order exponential decay. Three pathways of water movement in the bund could be distinguished, namely, vertical infiltration, lateral seepage and flow along the bund–bedrock interface. The primary water seepage channel in the bund was likely to be the bund–bedrock interface (accounting for around 80% of the total flow). These results provide preliminary realisation of water movement mechanisms in the purple soil bunds on sloping farmland and inform management options for bund stability maintenance.

Characterization and Taxonomic Classification of Soils in Onigambari Forest Reserve South Western Nigeria

A soil survey of Onigambari forest reserve in Oyo State, Nigeria was carried out. Three soil mapping units Established-Teak-Plantation (ETP), Natural-Forest (NF) and Farm-Land (FL) were identified with observation base on vegetative pattern. Morphological properties of the study area show that the soil unit ETP is deep and texture ranges from loamy-sand at the surface to sandy clay loam in the subsurface. The soil unit NFand FL is not deep due to presence of hard pan but the texture ranges from sandy-loam to sandy-clay and loamy-sand to sandy-clay respectively. Physical properties of the soils showed the bulk density of the soils to be moderately good for growing plant with high porosity. The soils chemical properties indicate that the pH value of the soils in ETP, NF and FL are slightly acidic and organic-matter was very low in the soils of ETP compared to NF and FL soils. The total-nitrogen values of the soils in the area changed irregularly with depth and values ranged from 0.028 to 0.1g kg-1 in ETP, 0.05 to 0.25g kg-1 in NF, the value ranged from 0.03 to 0.26 g kg-1 in FL. 0.03 to 0.26 g kg-1. According to USDA soil Taxonomy system, all the profiles pits in the study area showed distinguishing characteristics of the order Alfisols, therefore the soils are classified as Alfisols. Profile in the Established-Teak-Plantation is classified as Typic isohyperthermic paleustalfs, Profiles Natural-Forest and Farm-Land with petro-plinthic material within 100cm of the soil surface qualified as plinthic isohyperthermic paleustalfs.

Influence of soil moisture on energy requirement of rotary tilling

The rotary tiller with ‘L’ shaped blades was examined for torque, power and specific tilling energy requirements to attain optimum soil-machine operational parameters. The three levels of moisture content (11.4%, 12.8% and 14.6% (d.b)), three speed ratios of 20 (?1), 12 (?2) and 9 (?3) at different passes (first, second and third) with rotational speed of 262 rpm were selected for study. The observations indicated inverse relation between torque and power requirement to moisture content. The lowest value of torque of 16.54 N-m and 26.66 N-m was associated with sandy loam and clay loam soil under third pass and moisture content of 14.6 per cent. Similarly, the minimum power requirement of 0.452 kW and 0.699 kW was observed under analogous conditions of rotary tiller. The energy requirement was found to decrease with higher number of passes due to the breakdown of the hard pan and clod aggregate size. The specific tilling energy is strongly correlated with forward speed and less dependent on the number of the passes of rotary tilling.

Soil radioecological study in the Lomonosov diamond mining area (Arkhangelsk region, Russia)

The aim of the study was to obtain new data and on their basis to analyze soil radioactivity in the Lomonosov diamond mining area (Arkhangelsk region, Russia).
 Location and time of the study: Field studies were carried out in the summer of 2018 in the Lomonosov diamond mining area (Arkhangelsk region, Russia).
 Methodology: To accomplish the task, 10 soil profile pits were cut, and 69 soil samples were taken from them. In the field, a description of soil morphology was carried out. Under laboratory conditions, the samples were dried at 105° C to constant mass. After weighing, the soil samples were placed in a Marinelli vessel to measure the specific activity of isotopes (cesium (137Cs), potassium (40К), radium (226Ra) and thorium (232Th)) by gamma spectrometry. Registration of gamma radiation from a counting soil sample, as well as processing of spectra was carried out using the Progress-gamma software and hardware complex FVKM.412131.002-03. The energy calibration of the gamma spectrometer to control the safety of the setup parameters was carried out after each measurement using a combined control source OISN-137-1 in a Marinelli vessel. The minimum exposure time of the counting sample was 3600 seconds. However, depending on the activity of the sample, the exposure time in individual samples with weak activity increased.
 Main results: As a result of field studies, it was found that Podzols, characteristic of the northern taiga, prevail in this area. The maximum activity of 137Cs was concentrated in the litter-peat (11.4–71.8 Bq/kg) and the humus horizon (26.7–105 Bq/kg). In the podzolic and Al-Fe-humus horizons there was a sharp decrease in the activity, reaching the lowest measured values in the parent rock (2–3 Bq/kg). The general tendency for the accumulation of natural isotopes 40K, 226Ra, and 232Th in the soil horizons was found to be weakly related to soil type or subtype. In some soil pits an increase in the natural radionuclides with depth was observed, being mostly the characteristic of 40K as its activity changed downwards from 82.6 to 652 Bq/kg. The 226Ra and 232Th activities in the soil profiles varied from 2.4 to 47.2 Bq/kg and from 2.9 to 40.6 Bq/kg, respectively. This is due to the fact that thorium is strongly sorbed by soil; therefore, its migration along the soil profile is poorly expressed, and the element is deposited in soils in the form of hydroxides. Loamy and clayey soils, were shown to be more enriched in radium, whereas sandy soils were poor in this element. The amount of radioactive elements, contained in a soil, is largely determined by the concentration of their isotopes in the underlying rocks. 
 Conclusion: The peaks of increasing concentration in the Al-Fe-humus horizons (BF, BFg) were associated with an increase in the content of the clay fraction, Fe, Al hydroxides, which increase the sorption capacity of soils. The litter-peat and the humus horizon act as a biogeochemical barrier that retains radioactive elements in the soil for a long time. Due to the high filtration capacity of podzols, the underlying horizons are not reliable barriers. 137Cs and other radioisotopes can bind with humic substances, oxides and hydroxides of iron and aluminum, form humus-ferruginous complexes, precipitate as new soil formations, e.g. become part of the mineral composition of hard pans. The distribution of natural radioisotopes 40K, 226Ra and 232Th was found to be more chaotic and more related to the composition of the constituent rocks. The mobility and accumulation of radionuclides along soil profiles depends on the particle size distribution, the content of organic matter, sesquioxides, mineralogical composition, as well as on the temperature and water regime.

Investigation of Dam Integrity from Electrical Resistivity Methods: A Case of Erelu Dam, Southwestern Nigeria

DOI:10.17014/ijog.8.2.265-274Erelu dam is geologically within the Precambrian Basement Complex of southwestern Nigeria, which serves a principal source of water supply to an increasing population; currently at about 779,318. In an attempt to investigate the integrity of the dam, horizontal resistivity profiling (HRP) of dipole-dipole and Schlumberger’s vertical electrical sounding (VES) approaches were explored to delineate the lithologic layers, facies, and geologic structures in the subsurface of the dam. The HRP revealed changes in subsurface conductivity that depicts lateritic hard pan and saturated rock blankets at shallow depth. The vertical geo-electric section delineated predominant four lithologic units. The regolith is 7 m thick and constitutes the vertical rock fill impervious cores of the dam, which is underlained by saprolitic and fresh bedrock. The region of weathered rock depression coincided the shallow saturated anomalous zone and showed surface manifestation of fractured or unconsolidated terrain within the embankment. The fracture serves as conduit for seepage which could be responsible for possible loss in the reservoir water and increases its susceptibility to failure. It is recommended to keep monitoring the seepage with reservoir levels, by periodical geophysical and geotechnical measurements for the two (dry and wet) seasons.

Impact of Tillage Systems Equipped with Row Cleaners on Some Selected Soil Physical Properties under Wheat Cropping

Availability of improved tillage and herbicides during the last decades has enhanced the acceptance of conservation tillage. The main constrain to this type of tillage, particularly, zero tillage is high level of crop residue, which reduces seeding quality, soil temperature, etc. Accordingly, a study was initiated by equipping row cleaners with no-till system under wheat cultivation. For this purpose, a field experiment was laid in a split-split plot design with three types of row cleaners, three sub-treatments of travelling speed, and two sub- sub treatments of tillage depth. The results indicated that the soil temperature was highly affected by percent of residue left. Measurement of penetration resistance indicated that hard pan was not a potential limiting factor for the crop root development. The soil water was increased by 8.83%, 15.33% and 12.54% under no-till without row cleaner (M1), no-till with narrow row cleaner (M2) and no-till with wide row cleaner (M3) respectively compared to that under conventional tillage (CT). The percentage of soil loss reduction under M1, M2 and M3 were 53.11%, 59.62% and 50.51% compared to that under CT. The water losses were also reduced by 46.19%, 48.65% and 46.86% under these treatments as compared with CT.

Water retention and irrigation characteristics of Vertisols in northwestern Turkey

The study comprised the analyses of 105 soil samples, located across the Thrace region of Turkey, collected from the horizons and sub-horizons of 16 soil pedons, classified as the Haploxerert and Calcixerert Great Groups of the Vertisol Order. Fundamental soil hydraulic and irrigation management properties, such as water retention and infiltration rate of the soils were evaluatedd along with the content and type of the dominating clay mineral. Results obtained for the major properties related to irrigation management such as the total total water holding capacity (TWHC), total available moisture (TAM) and the final infiltration rate of the studied soils, showed close dependence on the varying clay contents and clay types, and varied in the ranges of 393 and 635 mm/100 cm; 128 and 244 mm/100 cm; and 1.0–80.0 mm/h, respectively. In addition, it was determined, that values of the studied hydraulic characteristics are influenced also by the relative abundance and crystallinity degree of the dominant and accompanying clay mineral; availability of cracks, hard pans, self-mulching (pedoturbation) and gilgai formation. The diversity of the morphological, physical and/or chemical properties revealed that the studied soils required distinctive approaches and techniques in terms of irrigation management. The Türkgeldi Vertisol (Türkgeldi State Farm D11 and D12 locations) is an appropriate example for decreased pedoturbation and/or maturation in physical pedogenesis and in turn development of a stable soil structure, despite the high clay size particle and ssmectite contents throughout the profile.

Rice–wheat system in the northwest Indo-Gangetic plains of South Asia: issues and technological interventions for increasing productivity and sustainability

Puddled transplanted rice (Oryza sativa L.) followed by intensively tilled wheat (Triticum aestivum L.) (R–W) is the most predominant cropping system and the lifeline for billions of people in South Asia. The cultivation of R–W system requires high amounts of water, nutrients and energy, resulting in increased production costs and increased emissions of greenhouse gases. There are also increasing concerns of yield stagnation or decline in the R–W system, with increasing environmental footprints. Hence, the sustainability of the R–W system in South Asia, particularly in the northwest Indo-Gangetic Plains (IGPs), has been questioned and heavily debated. Based on the findings from peer-reviewed literature, this review aims to identify unsustainability issues and research gaps in the R–W system and propose possible solutions to mitigate those issues and technological interventions to close the research gaps. Among the unsustainability issues that the review has identified are declining crop, water and land productivity, deterioration of soil health, emissions of greenhouse gases due to intensive tillage and residue burning, deepening of groundwater levels and shift in weed flora and development of herbicidal resistance in crops. Potential solutions or technological interventions to mitigate the unsustainability issues include resource conservation technologies (RCTs) such as rice residue management, reduced tillage, laser land leveling, soil matric potential based irrigation scheduling, delayed rice transplanting, cultivation on permanent raised beds, direct-seeded rice (DSR), mechanical transplanting of rice and crop diversification with legumes. These interventions have the potential to reduce energy, water and carbon (C) footprints from the R–W system. Rice residue retention with Happy Seeder and adoption of zero tillage (ZT) for wheat establishment have significantly lowered the environmental footprints, with increased soil C sequestration due to additions of large amounts of plant-mediated C input. Residue mulching has helped increase root length of wheat by ~25% and root length density by ~40% below 15 cm depth, compared to no mulching. The Happy Seeder saved ~30% of irrigation water due to reduction of soil evaporation by ~42–48 mm through residue mulching. Crop cultivation on permanent raised beds is less energy-intensive and results in ~7.8–22.7% higher water use efficiency yet crop productivity in long run could be affected due to reduced root growth on beds. The puddled transplanted rice (PTR) established under wet tillage, however, can decrease the water percolation losses by 14–16% and crop water demand by ~10–25%, and it forms hard pan in soil plough (7–10 cm) layer due to increased soil bulk density. Water stagnation under continuously flooded PTR is the major source of methane emissions with serious environmental implications. Methane emissions from flooded rice can increase global warming potential by 18.1–27.6% compared to intermittently flooded rice with multiple aerations. The conventional tillage can favor the germination of grassy weeds in wheat, while the broad-leaved weeds increase under zero tillage. Zero tillage with mulch load conserved ~4.0% higher moisture due to ~2.3% lesser soil temperature and evaporated ~27.6% lesser than the conventional tillage. Delayed rice transplanting with short-duration variety has potential of saving of up to ~140 mm of irrigation water in the semiarid areas of NW IGPs. Although the DSR had lower yield potential than the PTR, it saved ~50% irrigation water. The laser land leveling technology saved ~30% irrigation water and ~25% electricity and had a yield advantage of ~4%, compared with PTR on un-leveled fields. The mechanical transplanted rice had higher grain yield and more water saving than the manual transplanting or DSR. The review demonstrates that a single technology may not be applicable everywhere and integrated approaches with the multiple criteria—productivity, economics, energy and environmental sustainability—would be required to address the unsustainability issues of the R–W system of the NW IGPs. There is a need to elucidate and disseminate various site- and context-specific RCTs appropriate for the region to address the unsustainability issues and challenges of the system. Sustainable R–W production technologies with reduced water, energy and C footprints are required for increased water and energy productivity and C sequestration for the NW IGPs of South Asia.

Conservation Agriculture: A Way for Soil Water Conservation

World population is going on increasing, it may be 2.4 billion by 2050, but stabilizing the yield of crop is questionable in Indian agriculture due to improper management of agricultural land. Excess tillage accelerate the organic matter oxidation present on the top soil, soil erosion and creates subsurface hard pan. This makes the field unsuitable for cultivation of crops in future. Climate change is worsening the situation by imposing water scarcity in India. So to evade these problems, conservation agriculture is the only way. Main objectives of conservation agriculture is reducing tillage, year round cropping, crop rotation, mulching may be live or residue. Due to reduced mechanical tillage, activity of micro flora and macro flora get increases that improves biological tillage of soil, that in turn improves soil structure and enhances the plant growth. Most of the studies showed that the cost of wheat production and CO2 emission from the field is reduced when conservation agriculture was fallowed in rice-wheat cropping system. Crop rotation and also mixed cropping improves soil fertility and also it reduces soil erosion. It can be a part of climate smart agriculture. It reduces greenhouse gas emission and also it can improve carbon sequestration. Considerably it can save 20-30% of water.

Sesbania aculeata a Cost Effective Alternative to Enhance the Soil Health and Productivity of Rice-Wheat System

Background: Cereal based cropping systems are predominantly followed in south Asia because of higher productivity and profitability and ensuring food security. Rice is grown once a year in rotation mainly with wheat. Continuous cultivation of rice results in the formation of a hard pan below the ploughing layer, which may act as a barrier to normal root growth of the subsequent wheat crop. Consequently, soil bulk density is increased and hydraulic conductivity is reduced thus leading to non-conducive soil physical characteristics for the subsequent wheat crop. To reduce these ill effects, FYM is used as organic source. But live stock population is not increasing in the ratio as it is required to meet the FYM demand. Organic source requirement cannot meet through use of FYM in rice-wheat system, which is vital for food security point of view. There is need of alternate cost effective source of FYM which could enhance the soil health as well as productivity of rice-wheat system. The present study aimed to see the efficacy of growing green manure crop (Sesbania aculeata) as an alternative of FYM in the rice-wheat rotation. Methods: In this experiment conducted during kharif and rabi seasons of 2014-15 and 2015-16 in on-going long term permanent manorial trial since 1984 at research farm (Bihar Agricultural University, Sabour, Bihar, India), twelve treatments were taken under RBD in four replications. Observations and analysis were carried out by following the standard procedures. Result: The present investigation showed that combination of inorganic fertilizer and Sesbania aculeata helped in increasing yield as well as improving soil health. Sesbania aculeata can be used as a viable and cost effective alternative through partial substitution of inorganic fertilizers to enhance the soil health and productivity of rice-wheat system.

Effects of subsoiling depth, period interval and combined tillage practice on soil properties and yield in the Huang-Huai-Hai Plain, China

Compaction layers are widely distributed in the Huang-Huai-Hai Plain, China, which restrict root growth and reduce yields. The adoption of subsoiling has been recommended to disrupt compacted soil layers and create a reasonable soil structure for crop development. In this paper, the effects of subsoiling depth (30, 35 and 40 cm), period interval (2 or 3 years) and combined pre-sowing tillage practice (rotary cultivation or ploughing) on soil condition improvement was studied on a tidal soil in the Huang-Huai-Hai Plain. Seven tillage patterns were designed by combining different subsoiling depths, period intervals and pre-sowing. The evaluation indicators for soil condition improvement were as follows: thickness of the plough layer and hard pan, soil bulk density, cone index, soil three-phase R values, alkali nitrogen content, crop yield, and economic benefits. The results showed that subsoiling can significantly improve the soil structure and physical properties. In all subsoiling treatments, the depth of 35 or 40 cm at a 2-year interval was the most significant. The thickness of the plough layer increased from 13.67 cm before the test to 21.54–23.45 cm in 2018. The thickness of the hard pan decreased from 17.68 cm before the test to 12.09–12.76 cm in 2018, a decrease of about 40.07%. However, the subsoiling combined pre-sowing tillage practice, that is, rotary cultivation or ploughing, was not significant for soil structure and physical properties. For all subsoiling treatments, the soil bulk density, cone index and soil three-phase R values of the 15–25 cm soil layer were significantly lower compared to single rotary cultivation. Subsoiling was observed to increase the soil alkaline nitrogen and water contents. The tillage patterns that had subsoiling at the depth of 35–40 cm at a 2-year interval combined with rotary cultivation had the highest alkali nitrogen and water contents, which increased by 31.08–34.23% compared with that of the single rotary cultivation. Subsoiling can significantly increase the yield both of wheat and corn, as well as the economic benefits. The treatment of subsoiling at the depth of 35 cm at an interval of 2 years combined with rotary cultivation had the highest annual yield and economic benefits. For this treatment, the annual yield and economic benefits increased by 14.55 and 62.87% in 2018, respectively. In conclusion, the tillage patterns that involved subsoiling at a depth of 35 cm at a 2-year interval along with rotary cultivation are suitable for the Huang-Huai-Hai Plain.

Micronutrient distribution in soils of Ethiope region of Delta State, Nigeria

Investigation was carried out in Ethiope Region of Delta state, Nigeria to evaluate the distribution of micronutrients contents of oxisols. Ten farming communities were purposely selected in the region, and a total of 60 composite samples were collected with the aid of augers at a depth of 0 - 30 cm. The samples were air-dried at room temperature, sieved with 2 mm sieve mess before subjecting to laboratory analysis following standard procedures to determine the selected soil micronutrients (Fe, Cu, Mn, Zn). Data obtained were analyzed with descriptive statistics and analysis of variance while the least significance difference (LSD) at 5 % probability level was used to separate means. The relationship among nutrient parameters was shown with correlation analysis Results obtained indicated that the soils were moderate to slightly acidic, low in organic carbon and total nitrogen with medium contents of available P. Iron and Mn were found to be above the critical limits for crop production. At the same time, Cu and Zn were generally low. The high level of Fe might be a potential environmental problem upon complex reactions that will result in plinthite and hard pan formation that can restrict rooting and causing infiltration problem in the region. From the findings, it is advisable to apply organic fertilizers to boost the fertility of the soil and probably prevent plinthic layers development.

When do rice terraces become rice terraces?

Rice terraces located on sloped hills in mountainous areas are sometimes abandoned because of lack of labor and difficulties associated with cultivation. Recently, rice terraces also have been re-evaluated from the perspectives of water conservation or flood control. As a consequence, restoration has been conducted in many locations. In this study, we conducted field research on rice terraces in Okayama in order to determine when rice terraces become stable as rice terraces. Soil samples were obtained from depths of 0, 10, and 30 cm in abandoned fields and rice terraces restored in 2015, 2016, and 2017. The results showed that total carbon was the highest in abandoned fields and gradually decreased in the 2017-restored fields, followed by that in the 2016-restored fields. Particle analysis, particularly of surface soil, showed that the sand fraction decreased in order of abandoned fields, 2017-restored fields, and 2016-restored fields. We established that recently restored rice terraces have similar properties to those located on mountain hills, including few fine particles and high organic matter content in the surface soils. If the surface soil was cultivated and mixed with deeper soils, then the clay and silt content would gradually increase with time. Cone penetrometer analysis revealed that there was no clear evidence of a hard pan in the abandoned field and the 2017-restored field. In contrast, a hard pan had begun to develop in the 2016-restored fields and that it had become well established in the 2015-restored fields. Collectively, our findings indicate that although all rice terraces have a superficially similar appearance, recently recovered fields tend to have properties comparable to the properties of those located on mountain hills. These properties gradually change in the 2–3 years following restoration with the subsequent development of a well-established hard pan. We conclude that even rice terraces that have been abandoned for more than 30 years can develop clear properties of rice terraces within 3 years after restoration.

Assessing soil quality issues for crop production function based on farmers’ perception: An experience from Itapaji Watershed in Southwestern Nigeria

To successfully manage soil quality for sustainable crop production, there is need to identify issues affecting it. These are problems facing the capacity of soil to perform its functions and thus reducing its productivity. In addition, the similarities and differences between farmers’ perception of soil quality issues and that of soil scientist are very pertinent. This study, which was carried out at Itapaji watershed in Ikole local government area of Ekiti state, aims at identifying soil quality issues using participatory approach and conventional method. Diagnostic survey was carried out using participatory approach involving farmers’ judgement using questionaires. . The resultswere analysed to identify the soil quality issues from farmers’ perspectives. For conventional method, major soil types were identified and soil quality issues were identified using soil management assessment framework. The relationship between the soil issues from farmers’ interview and soil analysis were established by correlation analysis at α0.05. Soil quality issues identified by farmers are soil compaction, low soil fertility, termite infestation, crop wilt, hardpan formation, erosion, poor drainage and land use intensification. Low soil fertility is the most prominent with about 36.2 % impact on crop production in the watershed. Conventionally from soil analysis, CEC and organic matter are low which indicate low soil fertility; there is high acidity, shallow soil depth with presence of plinthite and hard pan. The farmers’ perception of soil quality and that of soil scientists correlate well (r = 0.70). There is therefore need for promotion of farmers’ participation by providing a forum for articulation of their opinions in mitigating low soil quality.

GIS-based spatial nitrogen management model for maize: short- and long-term marginal net return maximising nitrogen application rates

Crop growth models including CERES-Maize and CROPGRO-Soybean have been used in the past to evaluate causes of spatial yield variability and to evaluate economic consequences of variable rate prescriptions. In this work, a nitrogen prescription program has been developed that simulates the consequences of different nitrogen prescriptions using the DSSAT crop growth models. The objective of this paper is to describe a site-specific nitrogen prescription and economic optimizer program developed for computing spatially optimum N rates over long periods of weather and plant population for maize (Zea mays L.) using the CERES-Maize model. The application of the model was demonstrated on a field in Germany and another one in the USA to evaluate the concept across different environmental conditions. The user can determine the short- and the long-term optimal spatial nitrogen prescription based on crop price and nitrogen cost. The program simulated short-term optimum N applications that averaged 9% (McGarvey field, USA) and 48% (Riech field, Germany) lower than the uniform rates actually applied in the fields. The program indicated different site-specific N management options for low and high yielding fields under the assumed prices for maize and N. The implementation of a site-specific plant population management was investigated. A site-specific-optimization of plant population showed a higher profitability in the heterogeneous field in Germany. Hard pan depth, hard pan factor, root distribution factor and the percentage of available soil water across the heterogeneous field were useful indicators in predicting the magnitude of site-specific plant population benefits over uniform rates.