Build-up Of Soil Organic Matter Research Articles

Assessment of nutrient flows in maize-based farming system by smallholder farmers for sustainable production in Ikara, Kaduna State

Nutrient depletion is one of the major causes of decreased crop yield, and a threat to food security and sustainable crop production. NutMon- toolbox was used to determine nutrient flows and partial nutrient balances of maize-based smallholders’ farming system. Data was collected using structured questionnaire from 15 randomly selected farmers, with five farmers each in three villages. Composite soil samples were also taken from each of the three plots. At crop maturity, samples of crop products and residues were randomly taken from the selected fields. Nitrogen, P and K contents in soil and crop material was used to calculate nutrient flows and partial balances. Results obtained revealed that mineral fertilizer flow, averaged 349.20kg N yr-1 and 81.45kg K yr-1 and were lower than 376.65kg N yr-1 and 431.44kg K yr-1 organic input. However, phosphorus in mineral fertilizer (55.78kg P yr-1) was higher compared to phosphorus (51.06 kg P ha-1 yr-1) in organic input. Nitrogen, phosphorus and potassium for maize seeds and crop residue were all negative. The partial nutrient balances were positive 53.45kg N ha-1 yr-1 and 79.40kg K ha-1 but negative 1.10kg P ha-1 yr-1. Harvesting of crops for food, without incorporation of crop residue into the soil, were the most important sources of nutrient mining in smallholder production system. Integrated soil fertility management practices that favour the buildup of soil organic matter and use of animal manure should be encouraged through effective extension services at Ikara, Kaduna State, Nigeria.

Conversion of Marginalized Tea Lands into Timber Plantations and its Impact on Soil Organic Carbon Content: A Case Study in Central Highlands of Sri Lanka

Tea (Camellia sinensis) plantations can be in production for about 100 years under well-managed conditions. However, soil degradation makes the tea lands marginalized and uneconomical. Land use conversion is an option for marginalized tea lands that could gain numerous environmental and economic benefits. This study estimated and compared the soil organic carbon stocks (SOC) in the surface soil layer (0–30 cm) of marginalized tea lands against those converted to timber plantations in the Badulla and Nuwaraeliya districts. Disturbed and undisturbed soil samples were collected from the top layer (0-30 cm) of the selected sites of marginalized tea lands and those converted to timber plantations for analysis. Organic matter percentage in the site-level dry soil samples was analysed using the loss on ignition method. The final carbon stocks (t C ha-1) for samples from both land use types were then estimated using the SOC percentages and bulk density estimates. The carbon stocks for the soil samples collected at marginalized tea lands and the marginalized tea lands converted to timber plantations were then statistically analysed (descriptive statistics, normality tests and two-sample t-tests) using Minitab 21.2 software. The pH of marginal tea lands (5.34±0.14) and the marginal tea lands converted to timber plantations (5.20±0.13) was slightly acidic in nature. The bulk density estimates of marginalized tea lands and marginalized tea lands converted to timber plantations were very close and estimated as 1.15±0.02. The statistical analysis showed that overall mean SOC was significantly higher under the marginalized tea lands converted to timber plantations (155.3±10.0 t C ha-1) compared to the marginalized tea lands (126.7±5.8 t C ha-1). Land use conversion has increased the SOC stocks gradually after forest establishment. The increased carbon stocks could be attributed to consistent addition of litter layer on the soil, less soil disturbance, and retarded soil erosion contributing to the buildup of soil organic matter and SOC. On the other hand, low carbon stocks in the marginalized tea land could be attributed to unsustainable agronomical practices. Our findings suggest that converting marginalized tea lands in central highlands into timber plantations could enhance the sequestration of atmospheric CO2, significantly contributing to climate change mitigation.
 Keywords: Soil organic carbon, Land use change, Climate change, Tea plantations

INFLUENCE OF TEAK (Tectona grandis) LINN ON SOIL NUTRIENTS STATUS IN AKANGA TEAK PLANTATION, NASARAWA STATE, NIGERIA

Teak species have been found to have effects on soil properties different from those of indigenous natural forests in terms of organic matter accumulation and soil properties on the forest floor. This research aims at evaluating the physico-chemical properties of soil under Teak plantations in Akanga Teak plantations, Nigeria. Soils were sampled and analyzed based on procedures described by Bouyoucos, Day, and Reeuwijk. Based on the results, soil particle size from the plantation had the highest percent of sand (74.5±1.1). There was a fluctuation of soil pH between the age series, 1981 age series had the highest pH (6.2±0.0) in both seasons. The nitrogen content had a steady declined as the plant age increased, while the organic matter and phosphorus content increased with the age of the plant species in the area. There was a decline in soil nutrients during the wet season, which also coincided with the active growth period of forest trees. Thus, it is evident from this study that monoculture plantation of exotic species may lead to an initial reduction of soil organic content and nutrient elements in the soil; then a gradual buildup of soil organic matter and exchangeable cations with age.

Utilisation of Miscanthus x giganteus L. Based C-Rich Fertilisers for N Immobilisation and Microbial Biomass Build-Up in a Crop Rotation

Cultivation of perennials such as Miscanthus x giganteus Greef et Deuter (Mis) combines the provision of ecosystem services and the generation of additional carbon sources for farming. The potential of Mis based fertilisers, regarding immobilisation of inorganic nitrogen (N) and build-up of soil organic matter (SOM), was tested in a field trial. Therefore, a crop rotation of winter barley (Hordeum vulgare L.), mustard (Sinapis alba L.) as catch crop, sugar beet (Beta vulgaris L.) and winter wheat (Triticum aestivum L.) was set up. The tested treatments were a mixture of Cattle Slurry (CS) and Mis, a mixture of CS and Wheat Straw (CS–WS), Cattle Manure (CM) from Mis shredded bedding, CM from WS shredded bedding, a pure CS, Urea Ammonium Nitrate (UAN) and a treatment without any N applied (NoN). When the carbon-rich fertilisers (both mixtures and manures) were applied to cereals, they led to a slight N immobilisation compared to pure CS, whereas differences were mostly not significant. Furthermore, Mis fertilisers were at least as efficient as WS-based organic fertilisers in inducing a contribution of SOM build-up and in reducing inorganic N before winter and thus preventing N losses, whereas differences were mostly not significant.

Bioenergy production effects on SOM with depth of loblolly pine forests on Paleaquults in southeastern USA

Managed loblolly pine (P. taeda L.) forests comprise a major land-use across the “wood basket” of the southeastern US. Lower coastal plain loblolly pine forests can enhance carbon (C) storage in fast-growing vegetation and soils, representing a significant opportunity to manage these forests for improved soil health through an understanding of soil C and nitrogen (N) storage. Furthermore, these forests have unrealized potential to produce biomass for emerging bioenergy markets. Despite this, very little is known about how intensified management (herbaceous bioenergy production) of these forests influences short-term soil organic C (SOC) and soil organic N (SON) pools in surface and subsurface soil horizons. The field site was located in the Lower Coastal Plain of North Carolina, USA in which trees were planted in bedded (e.g., raised) rows (bed) and intercropped with or without switchgrass (P. virgatum L.) between the bedded rows of trees (interbed). Soils were collected from four depths (0–5, 5–15, 15–30, and 30–45 cm) and two locations (bed and interbed regions) and fractionated into light and heavy mineral-associated SOC and SON pools using a sequential density fractionation technique. Bulk soil SOC and SON concentration as well as C:N ratio decreased with depth for both treatments, while 15N became enriched. Free and occluded lighter fractions (< 1.65 g cm−3) had higher SOC and SON concentration (~45% C and ~ 1.15% N) compared to medium (1.65–2.00 g cm−3) and heavy (> 2.00 g cm−3) fractions. At the 0–5 cm depth in interbeds, SOC and SON were concentrated in the free light fraction (~45%), but transitioned to being concentrated in the heaviest mineral-associated fraction at the 15–30 (~55%) and 30–45 (~70%) cm depth. The 15N analysis of density fractions indicated progressive enrichment with increasing density, suggesting increasing incorporation of microbially-derived products into stable mineral-associated soil organic matter (SOM) pools. In the pine-switchgrass treatment, SOC and SON concentrations were higher in the light and medium fractions in beds and interbeds compared to the pine only treatment, particularly at the 30–45 cm depth. The C:N ratio in the pine-switchgrass treatment was higher compared to the pine only treatment indicating inputs of new plant-derived organic matter. Furthermore, the δ13C stable isotope signature was enriched in both the occluded light fraction (1.65 g cm−3) and the mineral-associated fraction (1.65–1.85 g cm−3). Our results suggest that switchgrass intercropping is contributing to the early buildup of SOM in particulate and mineral-associated SOM pools possibly through additions of new root-derived organic matter and the positive effect on soil microbial activity through priming of microbes.

How vegetation patches drive soil development and organic matter formation on polar islands

As Antarctica is strongly affected by climate change and global warming, the factors that mainly determine soil development might also shift from the dominance of physical to biochemical processes. Vegetation is restricted to the margins of the Antarctic continent with the Antarctic Peninsula being a region of patchily distributed vegetation. While on James Ross Island in the Weddell Sea only cryptogams can be found, on King George Island in the Southern Ocean also vascular plants are present. As rates of soil development and the build-up of soil organic matter are very low in these polar conditions, it can be hypothesized that vegetation patches comprise hot spots for biogeochemical soil processes. To analyze the effect of vegetation on soils in maritime Antarctica, we investigated vegetated and vegetation-free soils from both islands. On both islands, we found clearly higher carbon and nitrogen contents in vegetated soils. Using physical fractionation, we could demonstrate that the amount of free and occluded particulate organic matter is also higher in soils under vegetation, but at the same time, that clay-sized mineral-associated organic matter contributes most to carbon storage in all soils. The dominance of aromatic compounds in vegetation-free soils was disclosed by 13C NMR spectroscopy as well as a larger proportion of compounds with a lower molecular weight in vegetated soils. Thus, vegetation patches lead to soil organic matter containing higher amounts of bioavailable substrates that can be assumed to foster microbial activity and thus drive further soil development in a warmer future. However, in the cold arid environments a propagation of aridity might result in vegetation dieback and thus in a ceasing of biological soil activity driving a slowing of soil development.

Nitrogen Immobilisation and Microbial Biomass Build-Up Induced by Miscanthus x giganteus L. Based Fertilisers

Cultivation of Miscanthus x giganteus L. (Mis) with annual harvest of biomass could provide an additional C source for farmers. To test the potential of Mis-C for immobilizing inorganic N from slurry or manure and as a C source for soil organic matter build-up in comparison to wheat (Triticum aestivum L.) straw (WS), a greenhouse experiment was performed. Pot experiments with ryegrass (Lolium perenne L.) were set up to investigate the N dynamics of two organic fertilisers based on Mis at Campus Klein-Altendorf, Germany. The two fertilisers, a mixture of cattle slurry and Mis as well as cattle manure from Mis-bedding material resulted in a slightly higher N immobilisation. Especially at the 1st and 2nd harvest, they were partly significantly different compared with the WS treatments. The fertilisers based on Mis resulted in a slightly higher microbial biomass C and microbial biomass N and thus can be identified as an additional C source to prevent nitrogen losses and for the build-up of soil organic matter (SOM) in the long-term.

Sustainable Cereal Straw Management: Use as Feedstock for Emerging Biobased Industries or Cropland Soil Incorporation?

Sustainability goals regarding biobased chemicals and fuels can lead to increased demand for cereal straw, which could lead to undesirable effects on soil organic matter (SOM) content. The aim of this study was to evaluate the effects of removing straw on SOM, using a life cycle approach based on agricultural statistics and soil carbon modelling. This regional evaluation in southern Sweden showed that the general restrictions on straw removal recommended in many European studies, with demands on the incorporation of at least half of the aboveground straw, is not an efficient means of SOM preservation. Unrestricted straw removal in combination with the cultivation of intermediate crops leads to a much higher SOM build-up. Such measures will increase the availability of removable straw 2.5 times, at little extra cost. The findings of this study demonstrate the necessity of regional evaluation, taking new findings on the impact of straw incorporation on SOM into consideration. This is important for both regional emerging biobased industries, where unnecessary restrictions on straw removal might hamper the development of new production pathways, and for future sustainability in agriculture, where well-intended but inefficient SOM preservation strategies might hinder the implementation of more efficient measures.Graphic

Foliage Litter Decomposition of Agroforestry Shrub Species in Dello-Menna District of Bale Zone, Southeast Ethiopia

In agroforestry land use system soil productivity is maintained via the decomposition of tree/shrub species biomass input mainly foliage’s litter material. The quality of foliage litter material could be considerably varied among species. Hence, better soil management decision in agroforestry land use system remains on identification and use of the desirable species biomass input based on their decomposition characters. A study was conducted to evaluate the decomposition pattern of foliage litter materials of three agroforestry shrub species grown in Dello-menna district of Bale zone, Southeast Ethiopia. In the study single exponential model was employed to determine the decay rate of decomposing litter materials as the dependency of degradation rate on some litter chemical quality indices examined by using Pearson’s correlation coefficient. Results showed that the fastest decomposition rate was 0.037 day-1 for S. sesban followed by 0.017 day-1 for C. cajan and the least 0.014 day-1 for F. macrophylla. The explained variation in rate of decomposition among the tested species was found to be due to the effects of some litter chemical quality parameters. Accordingly lignin, cellulose, lignocelluloses index and C/N ratio were reported as impeding parameters whereas phosphorus and nitrogen identified as facilitators. Indeed, among the species S.sesban was recommended as the most suitable species for short term soil fertility management purpose. However, the accelerated decomposing character of S.sesban foliage litter may limits its potential for long-term build-up of soil fertility. Alternatively F.macrophylla majorly and C.cajan in some case can be considered for long-term build-up of soil organic matter. Keywords: Cajanus cajan, Flemingia macrophylla, Incubation period, Sesbania sesban DOI: 10.7176/JEES/11-3-02 Publication date: March 31 st 2021

Short-term cover crop carbon inputs to soil as affected by long-term cropping system management and soil fertility

Cover crops (CC) increase soil fertility via recycling of nutrients such as nitrogen (N) and buildup of soil organic matter, whereby CC contributes to climate change mitigation. The carbon (C) input to soil occurs via the input of plant material (shoot and root) and via phyllo- and rhizodeposition. However, the quantity of phyllo- and rhizodeposition from CC is largely unexamined, although this component potentially has a large contribution to microbial stabilization of C. Isotopic labeling with 13C to trace C flows and 15N to determine N2-fixation was conducted to test the short-term effect of the inclusion of winter vetch as a legume species to a CC mixture. The CC mixtures were established in a long-term experiment (1997–2019) with varying use of manure and CC cropping to test the effect of soil fertility on the behavior of the newly established CC mixtures. A significant reduction in the relative net phyllo- and rhizodeposition was observed with higher soil fertility. Interestingly, the quantity of net phyllo- and rhizodeposition was also reduced with higher soil fertility due to the lower relative phyllo- and rhizodeposition, despite a significantly higher CC biomass. Importantly, adjusting for unrecovered root fragments more than halved the calculated phyllo- and rhizodeposition, indicating that many published estimates are substantially overestimated. The use of CC during autumn provides an important window for C storage with both the input of plant biomass and belowground C investment being drivers of C storage.

Topsoil organic matter build-up in glacier forelands around the world.

Since the last glacial maximum, soil formation related to ice‐cover shrinkage has been one major sink of carbon accumulating as soil organic matter (SOM), a phenomenon accelerated by the ongoing global warming. In recently deglacierized forelands, processes of SOM accumulation, including those that control carbon and nitrogen sequestration rates and biogeochemical stability of newly sequestered carbon, remain poorly understood. Here, we investigate the build‐up of SOM during the initial stages (up to 410 years) of topsoil development in 10 glacier forelands distributed on four continents. We test whether the net accumulation of SOM on glacier forelands (i) depends on the time since deglacierization and local climatic conditions (temperature and precipitation); (ii) is accompanied by a decrease in its stability and (iii) is mostly due to an increasing contribution of organic matter from plant origin. We measured total SOM concentration (carbon, nitrogen), its relative hydrogen/oxygen enrichment, stable isotopic (13C, 15N) and carbon functional groups (C‐H, C=O, C=C) compositions, and its distribution in carbon pools of different thermal stability. We show that SOM content increases with time and is faster on forelands experiencing warmer climates. The build‐up of SOM pools shows consistent trends across the studied soil chronosequences. During the first decades of soil development, the low amount of SOM is dominated by a thermally stable carbon pool with a small and highly thermolabile pool. The stability of SOM decreases with soil age at all sites, indicating that SOM storage is dominated by the accumulation of labile SOM during the first centuries of soil development, and suggesting plant carbon inputs to soil (SOM depleted in nitrogen, enriched in hydrogen and in aromatic carbon). Our findings highlight the potential vulnerability of SOM stocks from proglacial areas to decomposition and suggest that their durability largely depends on the relative contribution of carbon inputs from plants.

Enhanced root carbon allocation through organic farming is restricted to topsoils

Soils store significant amounts of carbon (C) and thus can play a critical role for mitigating climate change. Crop roots represent the main C source in agricultural soils and are particularly important for long-term C storage in agroecosystems. To evaluate the potential of different farming systems to contribute to soil C sequestration and thus climate change mitigation, it is of great importance to gain a better understanding of the factors influencing root C allocation and distribution. So far, it is still unclear how root C allocation varies among farming systems and whether the choice of management practices can help to enhance root C inputs. In this study, we compared root C allocation in three main arable farming systems, namely organic, no-till, and conventional farming. We assessed root biomass, vertical root distribution to 0.75 m soil depth, and root-shoot ratios in 24 winter wheat fields. We further evaluated the relative importance of the farming system compared to site conditions and quantified the contribution of individual management practices and pedoclimatic drivers. Farming system explained one third of the variation in topsoil root biomass and root-shoot ratios, both being strongly positively related to weed biomass and soil organic C content and negatively to mineral nitrogen fertilization intensity. Root C allocation was significantly higher in organic farming as illustrated by an increase in root biomass (+40%) and root-shoot ratios (+60%) compared to conventional farming. By contrast, the overall impact of no-till was low. The importance of pedoclimatic conditions increased substantially with soil depth and deep root biomass was largely controlled by precipitation and soil texture, while the impact of management was close to zero. Our findings highlight the potential of organic farming in promoting root C inputs to topsoils and thereby contributing to soil organic matter build-up and improved soil quality in agroecosystems.

Stabilization of organic C in an Indo-Gangetic alluvial soil under long-term manure and compost management in a rice–wheat system

The nature of carbon input to soil, its transformation to soil organic matter (SOM), and the degree of protection from decomposition are important for long-term persistence of SOM. The effect of exogenous addition of organic matter on SOM build-up is well known; however, changes in quality vis-à-vis composition of added organic matter have been less investigated. It is necessary to ascertain the form under which C accumulates and how the composition of added organic matter influences the stabilization of soil organic C (SOC). Changes in composition of SOM were studied by fractionating the soil into coarse (cPOC; >250 µm) and fine particulate organic C (fPOC; 53–250 µm) and mineral-associated organic C (MinOC; <53 µm) and measuring the acid non-hydrolyzable C (NHC) as well as mineralizable C following repeated applications of farmyard manure (FYM), rice straw compost (RSC) and vermicompost (VC) in a rice (Oryza sativa L.)–wheat (Triticum aestivum L.) system field experiment. Addition of organic amendments for 10 years significantly increased SOC stocks and the increase was greatest with RSC (12.2 t ha−1) followed by FYM (9.1 t ha−1), and lowest with VC (8.5 t ha−1), compared with solitary application of NPK. The C accumulation in separated pools was influenced by the chemical composition of the organic source. Compost applications accumulated C preferentially in the MinOC pool, whereas the FYM accumulated a greater proportion of C as POC, particularly as fPOC. The differences were attributed to the lower C/N ratio and higher lignin content of RSC than FYM. The RSC application increased NHC stocks to a significantly greater extent than FYM and VC, indicating recalcitrance of the accumulated C. This was substantiated by the significantly lower C mineralization potential of RSC-amended soils compared to the FYM- and VC-amended soils. The results showed that addition of compost, besides leading to C build-up, improved C stabilization by imparting recalcitrance to SOC.

Termination method and time of agro-ecological service crops influence soil mineral nitrogen, cabbage yield and root growth across five locations in Northern and Western Europe

Abstract Agro-ecological service crops (ASCs), also known as cover crops, green manures or catch crops, can improve organic vegetable production in terms of weed suppression, nitrogen (N) recycling, or addition of N through symbiotic N2 fixation by legumes. Traditionally, ASCs are terminated through full incorporation into the soil (FI), but alternative termination without tillage is available by roller-crimping (RC). The applicability of RC to Northern and Western European climates has only been studied to a limited extend. The objective of this study was therefore to investigate the N dynamics involved in FI and RC of legume and cereal ASCs in organic cabbage production across Northern and Western European climates. Field experiments were conducted at one location in Estonia and in Denmark, and at three locations in Belgium during two cropping cycles (2015/2016 and 2016/2017) to assess the effect of ASC termination method in spring (FI and RC) and ASC species (pea, pea/cereal mixtures and cereals), compared with a bare soil control (BS), on soil mineral N content, N accumulation, yield, and root growth of a following crop of cabbage. Agro-ecological service crops, and in particular cereals, reduced N availability for succeeding cabbage compared with BS by 37–73%. Similar marketable cabbage yield was obtained under FI and BS in two out of four cases in Belgium, due to higher availability of soil mineral N when terminated earlier (April/May) than RC (May/June). However, FI reduced marketable yields by 36–98 % in the other cases in Belgium and in two out of four cases in Estonia and Denmark, where FI was conducted in May/June. Overall, cabbage marketable yields were reduced by 68–100% under RC compared to BS and FI in seven out of nine cases mainly due to reduced soil mineral N availability. Soil mineral N availability was lower under RC likely because of a slower mineralisation of ASCs and soil organic matter. Besides, the termination of ASCs close to the time of cabbage planting under RC increased pre-emptive competition on N. Cabbage marketable yield could be maintained under RC at fertilisation by 236 kg N ha−1 following pea in Denmark. Cabbage root growth was generally increased with higher above ground plant biomass across treatments in Estonia and Denmark, while the relationship was reverse under RC in East Flanders, indicating changes in resource allocation. Soil mineral N at harvest did not differ among treatments in deeper depth, showing no higher risk of N leaching from FI or RC. In conclusion, RC showed major yield reductions in the first and second year after conversion from spring tillage. Therefore, further investigations should verify improved yields under longer-term RC practice, e.g. due to build-up of soil organic matter, before implementation can be recommended in organic vegetable production in Northern and Western Europe.

Hypolithic communities shape soils and organic matter reservoirs in the ice-free landscapes of East Antarctica

The soils of East Antarctica have no rhizosphere with the bulk of organo-mineral interactions confined to the thin microbial and cryptogamic crusts that occur in open or cryptic niches and are collectively known as biological soil crust (BSC). Here we demonstrate that cryptic hypolithic varieties of BSC in the Larsemann Hills of East Antarctica contribute to the buildup of soil organic matter and produce several types of continuous organogenous horizons within the topsoil with documented clusters of at least 100 m2. Such hypolithic horizons accumulate 0.06–4.69% of organic carbon (TOC) with isotopic signatures (δ13Corg) within the range of −30.2 – −24.0‰, and contain from 0 to 0.38% total nitrogen (TN). The properties of hypolithic organic matter alternate between cyanobacteria- and moss-dominated horizons, which are linked to the meso- and microtopography patterns and moisture gradients. The major part of TOC that is stored in hypolithic horizons has modern or centenary 14C age, while the minor part is stabilized on a millennial timescale through shallow burial and association with minerals. Our findings suggest that hypolithic communities create a “gateway” for organic carbon to enter depauperate soils of the Larsemann Hills and contribute to the carbon reservoir of the topsoil at a landscape level.

Are horticulture-based land uses benign for fertility and health of soils in mid to high hills of the north-western Himalayan region?

ABSTRACT Soil fertility in many parts of the north‒western Himalayan region (NWHR) has declined owing to accelerated nutrient mining under existing crop regime. Therefore, this study aimed to assess effect of the predominant horticulture‒based land uses on soil fertility and health in mid and high hills of NWHR. Soil samples (0‒20 cm) were collected, analyzed for different soil chemical attributes (pH, electrical conductivity, organic C, available primary-, secondary-, and micro-nutrients), and compared across five key land uses: perennial grass (PG), peach orchard (PO), apple orchard (AO), field vegetable farming (VF), and protected vegetable farming (PV). Soils of the investigated land uses were neutral to near neutral in soil reaction (6.3‒6.8) except field vegetable and protected vegetable farming. Amount of soil organic C and labile organic C was significantly higher (p ≤ 0.05) in soils of apple orchards (18.6 g kg‒1 and 687.3 mg kg‒1, respectively) and peach orchards (20.4 g kg‒1 and 731.3 mg kg‒1, respectively) over others. An abrupt and significant increase in Olsen-P was recorded in soils of field vegetable farming (17.1 mg kg‒1) and protected vegetable farming (13.0 mg kg‒1), which shifted their nutrient index (NI) of P in to high category (≥ 2.33). The concentration of mineralizable-N in soil was statistically at par in soils under perennial grass and fruit orchards, while protected vegetable farming showed maximum soil mineralizable-N content (115.5 mg kg‒1) and NI of nitrogen (1.83). The NI was in high category (≥ 2.33) for copper, iron, and manganese in majority of the land uses. In view of the results, temperate fruit‒tree based land uses are benign in up‒keeping soil fertility and soil health, and needs promotion on large scale. Additionally, policies to create incentives for the build-up of soil organic matter and replenishment of the depleted soil macro and micro nutrients in vegetable-farmed lands are warranted.

Effect of conservation farming and biochar addition on soil organic carbonquality, nitrogenmineralization, and crop productivity in a light textured Acrisol in the sub-humid tropics.

Conservation farming (CF), involving basin tillage, residue retention and crop rotation, combined with biochar may help to mitigate negative impacts of conventional agriculture. In this study, the effects of CF on the amount and quality of soil organic matter (SOM) and potential nitrogen (N) mineralization were investigated in a maize-soya-maize rotation in an Acrisol in Zambia. A large field was run under CF for 7 years and in the subsequent three growing seasons (2015-2018), four management practices were introduced to study effects on soil characteristics and crop yield. We tested i) a continuation of regular CF (CF-NORM) ii) CF without residue retention (CF-NO-RES); iii) Conventional (CONV), with full tillage and removal of residues; and iv) CF with 4 ton ha-1 pigeon pea biochar inside basins and residue retention (CF-BC). The experiment involved the addition of fertilizer only to maize, while soya received none. Soya yield was significantly higher in CF systems than in CONV. Maize yields were not affected by the different management practices probably due to the ample fertilizer addition. CF-NORM had a higher stock of soil organic carbon (SOC), higher N mineralization rates, more hot-water extractable carbon (HWEC; labile SOC) and particulate organic matter (POM) inside basins compared to the surrounding soil (outside basins). Our results suggest that the input of roots inside basins are more effective increasing SOM and N mineralization, than the crop residues that are placed outside basins. CONV reduced both quality and quantity of SOM and N mineralization as compared to CF inside basins. CF-BC increased the amount of SOC as compared with CF-NORM, whereas N mineralization rate and HWEC remained unaffected. The results suggest benefits on yield of CF and none of biochar; larger impact of root biomass on the build-up of SOM than crop residues; and high stability of biochar in soil.

Temporal Impacts of Different Fertilization Systems on Soil Health under Arid Conditions of Potato Monocropping

The aim of this study was to determine temporary impacts of different fertilization systems on some labile soil biochemical and biological properties following potato monocropping under arid conditions. Field and incubation experiments were conducted to determine specifically soil organic carbon (SOC); dissolved organic carbon (DOC); dissolved organic nitrogen (DON); microbial biomass C (Cmic), N (Nmic), P (Pmic); bacterial and fungi counts; soil resistance index (SRI); net N mineralization (Nmin); and some enzyme activity. Levels of SOC; DOC; Nmin, Cmic, Pmic; bacteria and fungi counts; and soil respiration (SR) were significantly increased under organic and integrated fertilization systems compared with inorganic nano or NPK fertilization system, while levels of microbial biomass N (Nmic) and DON were markedly increased under nano or fertilizers compared to organic or integrated (organic + inorganic) fertilizers. By contrast, higher values of metabolic quotient (qCO2) were recorded in nano or fertilizer treatments suggesting that microbial biomass was less efficient under high maintenance of soil carbon. Enzyme activities of dehydrogenase (DH), β-glucosidase (βG), and acid phosphatase (Ac-P) were in the order of organic > integrated > inorganic fertilization systems, while enzyme activity of urease (UR) was in the vice versa order. Integrated fertilization system recorded greater levels of SOC; DOC; Nmin, Cmic, Pmic; and SR relative to inorganic fertilizers even though applied at lower rates. It is, therefore, important for soils under monocropping system to poise organic and inorganic fertilization system that enhances soil health and soil organic matter build-up.

Biochar Effects on Soil Properties and Wheat Biomass vary with Fertility Management

Biochar can improve soil health and crop productivity. We studied the response of soil properties and wheat growth to four rates of wood biochar (0, 11.2, 22.4, and 44.8 Mg ha−1) and two fertilizer rates [no fertilizer and fertilizer (90 kg N ha−1, 45 kg P ha−1, and 20 kg S ha−1)]. Biochar application increased soil organic matter (SOM), soil pH, phosphorus (P), potassium (K), sulfur (S) contents, and the shoot and root biomass of wheat. However, these responses were observed at biochar rates below 22.4 Mg ha−1, particularly in treatments without fertilizer. In fertilizer-applied treatments, soil nitrate levels decreased with an increase in biochar rates, mainly due to better crop growth and high nitrate uptake. However, without N addition, the high C:N ratio (500:1) possibly increased nutrient tie-up, reduced plant biomass, and SOM buildup at the highest biochar rate. Based on these results, we recommend biochar rates of about 22.4 Mg ha−1 and below for Walla Walla silt loams.

Dynamics and transformations of micronutrients in agricultural soils as influenced by organic matter build-up: A review

Abstract The dynamics and transformations of micronutrients (Zn, Cu, Fe, Mn, B and Mo) in soils, are governed by various factors like pH, EC, soil organic matter etc. Soil organic matter (SOM) is known to modify different physiochemical reactions that influence the available component of micronutrients. Soil organic matter favors reduced (lower redox potential) environment and enhances the accessibility of micronutrient cations in the soil. Also, SOM has direct and indirect impacts on nutrient transformations. Soil organic matter (SOM) also serves as source of soil organic carbon (SOC) comprising about 60% on a mass basis. Under reduced environment the addition of SOM increased complexed forms of micronutrients. Build-up of SOM in soil converts adsorbed fractions to more plant-accessible forms of micronutrients. Soil organic matter addition increases the water soluble and exchangeable forms of micronutrients in soil which further increase the uptake of micronutrients. High amount of SOM in soils assists the various reactions of micronutrients resulting in formation of more stable complexes of micronutrient. Soil organic matter binds more Zn, Cu, B and Mo compared to Fe and Mn because the former are less sensitive to redox changes. The accretion of organic matter near the soil surface increases transformations (towards adsorbed fractions) of Mn and Fe and possibly decreases the availability of Zn, Cu, B and Mo by causing their redistribution among other complex fractions.