Soil organic carbon storage and quality are impacted by corn cob biochar application on a tropical sandy loam

Purpose

Humic substances, which are integral components of total organic carbon (TOC), influence soil quality. The study aimed to investigate whether humic and non-humic fractions exhibit early, consistent, and measurable changes and affect TOC sensitivity and storage in a tropical sandy loam soils amended with corn cob biochar.

Materials and methods

There were four treatments with four replicates established in a randomized complete block design. Composite soil samples were taken from plots without biochar (CT), from plots incorporated with 15 t biochar ha^?1 (BC-15), and 30 t biochar ha^?1 without or with phosphate fertilizer (BC-30 and BC-30+P). The TOC, and humin, humic acid (HA), and fulvic acid (HA) fractions of soil organic carbon were determined for each treatment. The optical densities (400–700 nm) were measured on the soil-free extracts by spectrophotometry; the densities measured at 465 and 665 nm were used to calculate the E₄₆₅/E₆₆₅ ratios.

Results and discussion

The BC-30 and BC-30+P plots recorded the highest TOC, humin, humic acid (HA), and fulvic acid (FA) contents with respect to the lowest in the CT. The total exchangeable carbon stratification was significantly higher in all the biochar-treated plots relative to the CT. Spectral analysis showed higher values of E₄₆₅/E₆₆₅ (5.02 and 5.15) in the CT and BC-15-treated soils, respectively, compared with the BC-30 and BC-30+P-amended soils with E₄₆₅/E₆₆₅ ratios of 2.76 and 2.98, respectively.

Conclusions

Corn cob biochar applied to a tropical sandy loam:

? increased the concentrations of HA and FA and led to increased stratification of TOC, with a stronger effect on HA compared with FA;

? significantly lowered E₄₆₅/E₆₆₅ at the high biochar application rate of 30 t ha^?1, implying the dominance of high molecular weight humic acid-like substances, and increased degree of aromaticity of the TOC.

     

Biochar and biochar with N fertilizer as a potential tool for improving soil sorption of nutrients

Purpose

Biochar usually has a large specific surface area, and due to this, it increases the sorption capacity of the soil where it was applied. The objectives of this study were to (i) quantify the effects of biochar and biochar in combination with N fertilizer on the soil sorption parameters and (ii) quantify the effects of soil organic matter on the sorption parameters after application of biochar with and without N fertilizer.

Materials and methods

The experiment was established on Haplic Luvisol at the locality of Dolná Malanta (Slovakia) in 2014. The soil samples were collected once a month from the depth 0–0.2 m during 2014 to 2016. The field experiment included three rates of biochar application (B0?=?no biochar, B10?=?biochar at the rate of 10 t ha^?1, B20?=?biochar at the rate of 20 t ha^?1) and three levels of N fertilization (N0?=?no nitrogen, N40?=?nitrogen at the rate of 40 kg ha^?1, N80?=?nitrogen at the rate of 80 kg ha^?1).

Results and discussion

Overall, the decrease of the average values of hydrolytic acidity due to biochar and biochar combined with N fertilization resulted on average in an increase of sum of basic cation (SBC), cation exchange capacity (CEC), and sorption capacity of soil organic matter (CEC_SOM) in all treatments. However, this effect was the most intensive in B10N40. Despite the fact that the average values of sorption parameters improved, its dynamics during the investigated period were different. A significant decrease in CEC was observed from 2014 to 2016 in all treatments, except B0N0 and B10N0. A stable trend in CEC_SOM was observed only in B10N40. Humic substances and humic acids had a statistically significant positive effect on the SBC, CEC, and CEC_SOM only in B20N0 treatment. Negative correlations between the above mentioned parameters were observed in B10N80 treatment.

Conclusions

We conclude that the application of biochar and biochar combined with N fertilization had a positive influence on sorption parameters. However, its effects on SBC, CEC, and CEC_SOM decreased over time after its application.

     

Short-term effects of organo-mineral enriched biochar fertiliser on ginger yield and nutrient cycling

Purpose

Biochar has agronomic potential but currently is too expensive for widespread adoption. New methodologies are emerging to reduce the cost such as enriching biochar with nutrients that match crops and soil requirements. However, the effects of biochar-based fertilisers on plant yield and soil nutrient availability have not been widely examined. This study investigated the effects of a novel organo-mineral biochar fertiliser in comparison to organic and commercial biochar fertiliser on ginger (Zingiber officinale Canton).

Materials and methods

There were four treatments: (1) commercial organic fertiliser (5 t ha^?1), as the control; (2) commercial biochar-based fertiliser (5 t ha^?1); (3) organo-mineral biochar fertiliser at low rate (3 t ha^?1); and (4) organo-mineral biochar fertiliser at high rate (7.5 t ha^?1). A replicated pot trial was established with black dermosol soil and ten replicate pots for each treatment. Ginger was planted and grown for 30 weeks. Plant growth, biomass, foliar nutrients and water extractable soil nutrients including phosphorus (P), potassium (K) and calcium (Ca) were examined.

Results and discussion

High rate organo-mineral biochar fertiliser increased soil P and K availability at week 30 (harvest) after planting, compared to all other treatments and low rate organo-mineral biochar fertiliser performed similarly to the organic control for P and K. High rate organo-mineral biochar fertiliser increased total foliar nutrient content at week 30 in P, K and Ca compared to commercial biochar fertiliser. High rate organo-mineral biochar fertiliser improved the commercial value of ginger (+?36%) due to a shift in the proportion of higher grade rhizomes. Low rate organo-mineral biochar fertiliser plants displayed similar yield, total dry and aboveground biomass to commercial organic fertiliser. Commercial biochar fertiliser had significantly lower biomass measures compared with other treatments as the rate applied had lower nutrient concentrations.

Conclusions

Our results show organo-mineral biochar fertilisers could be substituted for commercial organic fertilisers at low rates to maintain similar yield or applied at high rates to increase commercial value where economically feasible.

     

Soil and nutrients losses under different crop covers in vertisols of Central India

Purpose

Accelerated erosion removes fertile top soil along with nutrients through runoff and sediments, eventually affecting crop productivity and land degradation. However, scanty information is available on soil and nutrient losses under different crop covers in a vertisol of Central India. Thus, a field experiment was conducted for 4 years (2010–2013) to study the effect of different crop cover combinations on soil and nutrient losses through runoff in a vertisol.

Materials and methods

Very limited information is available on runoff, soil, and nutrient losses under different vegetative covers in a rainfed vertisol. Thus, the hypothesis of the study was to evaluate if different crop cover combinations would have greater impact on reducing soil and nutrient losses compared to control plots in a vertisol.

This experiment consisted of seven treatment combinations of crop covers namely soybean (Glycine max) (CC₁), maize (Zea mays) (CC₂), pigeon pea (Cajanus cajan) (CC₃), soybean (Glycine max)?+?maize (Zea mays) ??1:1 (CC₄), soybean (Glycine ma x))?+?pigeon pea (Cajanus cajan) ?2:1 (CC₅), maize (Zea mays)?+?pigeon pea (Cajanus cajan) ??1:1 (CC₆), and cultivated fallow (CC₇). The plot size was 10?×?5 m with 1% slope, and runoff and soil loss were measured using multi-slot devisor. All treatments were arranged in a randomized block design with three replications.

Results and discussion

Results demonstrated that the runoff and soil loss were significantly (p?<?0.05) higher (289 mm and 3.92 Mg ha^?1) under cultivated fallow than those in cropped plots. Among various crop covers, sole pigeon pea (CC₃) recorded significantly higher runoff and soil loss (257 mm and 3.16 Mg ha^?1) followed by that under sole maize (CC₂) (235 mm and 2.85 Mg ha^?1) and the intercrops were in the order of maize?+?pigeon pea (211 mm and 2.47 Mg ha^?1) followed by soybean?+?maize (202 mm and 2.38 Mg ha^?1), and soybean?+?pigeon pea (195 mm and 2.15 Mg ha^?1). The lowest runoff and soil loss were recorded under soybean sole crop (194 mm and 2.27 Mg ha^?1). The data on nutrient losses indicated that the highest losses of soil organic carbon (SOC) (25.83 kg ha^?1), total nitrogen (N), phosphorus (P), and potassium (K) (7.76, 0.96, 32.5 kg ha^?1) were recorded in cultivated fallow (CC₇) as compared to those from sole and intercrop treatments. However, sole soybean and its intercrops recorded the minimum losses of SOC and total N, P, and K, whereas the maximum losses of nutrients were recorded under pigeon pea (CC₃). The system productivity in terms of soybean grain equivalent yield (SGEY) was higher (p?<?0.05) from maize?+?pigeon pea (3358 kg ha^?1) followed by that for soybean?+?pigeon pea (2191 kg ha^?1) as compared to sole soybean. Therefore, maize?+?pigeon pea (1:1) intercropping is the promising option in reducing runoff, soil-nutrient losses, and enhancing crop productivity in the hot sub-humid eco-region.

Conclusions

Study results highlight the need for maintenance of suitable vegetative cover as of great significance to diffusing the erosive energy of heavy rains and also safe guarding the soil resource from degradation by water erosion in vertisols.

     

URANIUM ACCUMULATION IN SOILS FROM LONG-CONTINUED APPLICATIONS OF SUPERPHOSPHATE

This paper describes the accumulation of uranium in soils from superphosphate applied annually to arable and grassland soils. Rates of application of superphosphate were equivalent to about 33kg P and 15 gU ha^?1 year^?1 in three experiments at Rothamsted and to about 37 kg P and 16g U ha ^?1 year ^?1 in one experiment in New Zealand. Most of the uranium (about 1300 g U ha ^?1) applied in superphosphate to the clay loam soil at Rothamsted since 1889 was retained, like P, in the plough layer of arable soils or was adsorbed by the organic surface layers of soils under permanent grassland. Uranium applied in superphosphate to grassland in New Zealand since 1954 (about 330 g U ha^?1) was also concentrated in the surface layers of the soil.     

Effect of plantain on nitrous oxide emissions and soil nitrification rate in pasture soil under a simulated urine patch in Canterbury,New Zealand

Purpose

The aim of this research was to quantify the effect of plantain (Plantago lanceolata L.) on soil nitrification rate, functional gene abundance of soil ammonia oxidisers, and the concomitant effect on nitrous oxide emissions from urine patches in a shallow, free-draining soil in Canterbury during late autumn/winter season.

Materials and methods

Urine was collected from dairy cows grazing either ryegrass/white clover (RGWC), 30% plantain (P30) mixed in with RGWC or 100% plantain (P100) pasture, and applied at two rates (700 or 450 kg N ha^?1) to intact soil blocks growing either RGWC, P30 or P100 pasture.

Results and discussion

Results showed that increased plantain content reduced N-concentration in urine from 7.2 in RGWC urine to 4.5 and 3.7 g N L^?1 in P30 and P100 urine, respectively. Total N₂O emissions and emission factors (EF₃) from urine-treated pastures were low, <?2 kg N ha^?1 and <?0.22%, respectively. Urine application at the lower urine N-loading rate of 450 kg N ha^?1 (i.e. representative of that in a P30 urine patch) resulted in 30% lower N₂O emissions (P?<?0.01) and 35% lower soil nitrate concentrations (P?<?0.001) compared to those at the higher urine loading rate of 700 kg N ha^?1 (i.e. representative of that in a RGWC urine patch). Increasing plantain content in the pasture sward from 0 to 30% and 100% with urine N applied at the same loading rate did not reduce N₂O emissions or nitrification compared to the standard ryegrass-white clover pasture. Cow urine derived from the different pasture diets had no effect on N₂O emissions, N transformation or ammonia-oxidiser abundance in soil compared to the RGWC urine applied at the same rate.

Conclusions

The main effect of plantain in this study appears to be related to the reduction in urine N-loading rate, rather than factors related to urine properties or plantain-soil interactions.

     

Nitrification,acidification, and nitrogen leaching from subtropical cropland soils as affected by rice straw-based biochar: laboratory incubation and column leaching studies

Purpose

Few studies have examined the effects of biochar on nitrification of ammonium-based fertilizer in acidic arable soils, which contributes to NO₃ ^? leaching and soil acidification.

Materials and methods

We conducted a 42-day aerobic incubation and a 119-day weekly leaching experiment to investigate nitrification, N leaching, and soil acidification in two subtropical soils to which 300 mg N kg^?1 ammonium sulfate or urea and 1 or 5 wt% rice straw biochar were applied.

Results and discussion

During aerobic incubation, NO₃ ^? accumulation was enhanced by applying biochar in increasing amounts from 1 to 5 wt%. As a result, pH decreased in the two soils from the original levels. Under leaching conditions, biochar did not increase NO₃ ^?, but 5 wt% biochar addition did reduce N leaching compared to that in soils treated with only N. Consistently, lower amounts of added N were recovered from the incubation (KCl-extractable N) and leaching (leaching plus KCl-extractable N) experiments following 5 wt% biochar application compared to soils treated with only N.

Conclusions

Incorporating biochar into acidic arable soils accelerates nitrification and thus weakens the liming effects of biochar. The enhanced nitrification does not necessarily increase NO₃ ^? leaching. Rather, biochar reduces overall N leaching due to both improved N adsorption and increased unaccounted-for N (immobilization and possible gaseous losses). Further studies are necessary to assess the effects of biochar (when used as an addition to soil) on N.     

Effect of treated farm dairy effluent on E. coli,phosphorus and nitrogen leaching and greenhouse gas emissions: a field lysimeter study

Purpose

Land application of farm dairy effluent (FDE) to pasture soils is the preferred practice in New Zealand. Recently, a new FDE treatment technology has been developed to recycle the water for washing the yard Cameron and Di (J Soils Sediments 2018). Here we report a lysimeter study to compare the leaching losses of Escherichia coli, phosphorus (P), and nitrogen (N) and emissions of greenhouse gases from the treated FDE compared with the untreated original FDE.

Materials and methods

Lysimeters were collected from a Balmoral silt loam soil (Typic Dystrudept, USDA) and installed in a field trench facility. Treatments included (1) treated effluent (TE), (2) a mixture of TE and recycled water (M), (3) untreated original FDE (FDE), and (4) water as control. The effluents were applied at a surface application rate of 24 mm on each lysimeter in May and again in September 2017. Measurements included leaching losses of E. coli, total phosphorus (TP), dissolved reactive phosphorus (DRP), total mineral nitrogen (TN), ammonium-N (NH₄⁺-N), and nitrate-N (NO₃^?-N); emissions of nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄); herbage yield; and N uptake.

Results and discussion

The results showed that E. coli, TP, and DRP leaching losses from the TE were 1.31?×?10¹⁰ cfu/ha, 0.26 kg P/ha, and 0.009 kg DRP/ha and from M treatments were 6.96?×?10⁸ cfu/ha, 0.18 kg P/ha, and 0.004 kg DRP/ha, respectively, which were significantly (P?<?0.05) lower than those from the FDE which were 4.21?×?10¹⁰ cfu/ha, 1.75 kg P/ha, and 0.034 kg DRP/ha, respectively. There were no significant differences in NO₃^?-N leaching losses amongst the different forms of effluents. There were no significant differences in total N₂O, CO₂ emissions, and CH₄ uptakes from the different effluents (P?<?0.05). Herbage dry matter yields and N uptakes were also similar in the different effluent-treated lysimeters.

Conclusions

Results from this research indicate that land application of the treated effluents (TE) or a mixture of TE plus clarified water (M) would result in significant environmental benefits by reducing E. coli and P leaching without increasing greenhouse gas emissions.

     

Nitrate leaching and residual soil nitrogen supply following outdoor pig farming

Abstract. Large nitrogen (N) inputs to outdoor pig farms in the UK can lead to high nitrate leaching losses and accumulation of surplus N in soil. We investigated the residual effects of three contrasting outdoor pig systems as compared to an arable control on nitrate leaching and soil N supply for subsequent spring cereal crops grown on a sandy loam soil during 1997/98 and 1998/99 harvest seasons. Previously, the pig systems had been stocked for 2 years from October 1995 and were designated current commercial practice (CCP, 25 sows ha^?1 on stubble), improved management practice (IMP, 18 sows ha^?1 on undersown stubble) and best management practice (BMP, 12 sows ha^?1 on established grass). Estimated soil N surpluses by the end of stocking in September 1997 were 576, 398, 265 and 27 kg ha^?1 N for the CCP, IMP, BMP and continuous arable control, respectively. Nitrate leaching losses in the first winter were 235, 198, 137 and 38 kg ha^?1 N from the former CCP, IMP and BMP systems and the arable control, respectively. These losses from the former pig systems were equivalent to 41–52% of the estimated soil N surpluses. Leaching losses were much smaller in the second winter at 21, 14, 23 and 19 kg ha^?1 N, respectively. Cultivation timing had no effect (P>0.05) on leaching losses in year 1, but cultivation in October compared with December increased nitrate leaching by a mean of 14 kg ha^?1 N across all treatments in year 2. Leaching losses over the two winters were correlated (P<0.001) with autumn soil mineral N (SMN) contents. In both seasons, spring SMN, grain yields and N offtakes at harvest were similar (P>0.05) for the three previous pig systems and the arable control, and cultivation timing had no effect (P>0.05) on grain yields and crop N offtake. This systems study has shown that nitrate leaching losses during the first winter after outdoor pig farming can be large, with no residual available N benefits to following cereal crops unless that first winter is much drier than average.     

Effects of two contrasting agricultural land‐use practices on nitrogen leaching in a sandy soil of Middle Germany

The objective of this study is to evaluate different agricultural land‐use practices in terms of N leaching and to give recommendations for a sustainable agriculture on sandy soils in Middle Germany. Soil mineral N (N_min) and leachate N were quantified at a sandy soil in N Saxony during 3 years. Two treatments were applied: intensive (I)—using inorganic and organic fertilizer and pesticides, and organic (O)—exclusively using organic fertilizer, legume‐based crop rotation, and no pesticides. Split application of mineral fertilizers did not result in substantial N losses at treatment I. Legumes induced a considerable increase of soil mineral N and particularly of leachate mineral N (N_{min_perc}) at treatment O. High N_{min_perc} concentrations (up to 78 mg N L^–1) were observed during as well as after the cultivation of legumes. These high N_{min_perc} concentrations are the reason why clearly higher N_{min_perc} losses were determined at treatment O (62 kg N ha^–1 y^–1) compared to treatment I (23 kg N ha^–1 y^–1). At both treatments, the quantity of N losses was strongly affected by the precipitation rates. Concentrations and losses of dissolved organic N (DON_perc) were assessed as above average at both treatments. The results suggest that the DON_perc concentration is influenced by precipitation, soil coverage, and organic fertilizers. Higher values were determined in the percolation water of treatment O. The average annual DON_perc losses amounted to 15 kg N ha^–1 at I and to 32 kg N ha^–1 at O. The average monthly percentage of DON_perc losses on the loss of the dissolved total N of percolation water (DTN_perc) ranged between <1% and 55% at O and between 2% and 56% at I. For the whole measuring period of 29 months, the relative amounts of DON_perc of DTN_perc (21% at O and 25% at I) were more or less the same for both treatments. The results show that DON_perc can contribute significantly to the total N loss, confirming the importance to consider this N fraction in N‐leaching studies. It was concluded that at sandy sites, a split application of mineral fertilizers, as applied at treatment I, seems to be more expedient for limiting the N leaching losses than legume‐based crop rotations.     

Crop yield and SOC responses to biochar application were dependent on soil texture and crop type in southern Quebec,Canada

Changes to soil nutrient availability and increases for crop yield and soil organic C (SOC) concentration on biochar‐amended soil under temperate climate conditions have only been reported in a few publications. The objective of this work was to determine if biochar application rates up to 20 Mg ha^?1 affect nutrient availability in soil, SOC stocks and yield of corn (Zea mays L.), soybean (Glycine max L.), and switchgrass (Panicum virgatum L.) on two coarse‐textured soils (loamy sand, sandy clay loam) in S Quebec, Canada. Data were collected from field experiments for a 3‐y period following application of pine wood biochar at rates of 0, 10, and 20 Mg ha^?1. For corn plots, at harvest 3 y after biochar application, 20 Mg biochar ha^?1 resulted in 41.2% lower soil NH on the loamy sand; the same effect was not present on the sandy clay loam soil. On the loamy sand, 20 Mg biochar ha^?1 increased corn yields by 14.2% compared to the control 3 y after application; the same effect was not present on the sandy clay loam soil. Biochar did not alter yield or nutrient availability in soil on soybean or switchgrass plots on either soil type. After 3 y, SOC concentration was 83 and 258% greater after 10 and 20 Mg ha^?1 biochar applications, respectively, than the control in sandy clay loam soil under switchgrass production. The same effect was not present on the sandy clay loam soil. A 67% higher SOC concentration was noted with biochar application at 20 Mg ha^?1 to sandy clay loam soil under corn.     

Impact of biochar addition to soil on greenhouse gas emissions following pig manure application

The application of biochar produced from wood and crop residues, such as sawdust, straw, sugar bagasse and rice hulls, to highly weathered soils under tropical conditions has been shown to influence soil greenhouse gas (GHG) emissions. However, there is a lack of data concerning GHG emissions from soils amended with biochar derived from manure, and from soils outside tropical and subtropical regions. The objective of this study was to quantify the effect on emissions of carbon dioxide (CO₂), nitrous oxide (N₂O) and methane (CH₄) following the addition, at a rate of 18 t ha⁻¹, of two different types of biochar to an Irish tillage soil. A soil column experiment was designed to compare three treatments (n = 8): (1) non-amended soil (2) soil mixed with biochar derived from the separated solid fraction of anaerobically digested pig manure and (3) soil mixed with biochar derived from Sitka Spruce (Picea sitchensis). The soil columns were incubated at 10 °C and 75% relative humidity, and leached with 80 mL distilled water, twice per week. Following 10 weeks of incubation, pig manure, equivalent to 170 kg nitrogen ha⁻¹ and 36 kg phosphorus ha⁻¹, was applied to half of the columns in each treatment (n = 4). Gaseous emissions were analysed for 28 days following manure application. Biochar addition to the soil increased N₂O emissions in the pig manure-amended column, most likely as a result of increased denitrification caused by higher water filled pore space and organic carbon (C) contents. Biochar addition to soil also increased CO₂ emissions. This was caused by increased rates of C mineralisation in these columns, either due to mineralisation of the labile C added with the biochar, or through increased mineralisation of the soil organic matter.     

Management effects on forms of phosphorus in soil and leaching losses

We should know the effects of soil use and management on the contents and forms of soil phosphorus (P) and the resulting potential for leaching losses of P to prevent eutrophication of surface water. We determined P test values, amounts of sequentially extracted forms of P, P sorption capacities and degrees of P saturation in 20 differently treated soils and compared these data with leaching losses in lysimeters. One-way analyses of variance indicated that most fractions of P were significantly influenced by soil texture, land use (grassland, arable or fallow or reafforestation), mineral fertilization and intensity of soil management. Generally, sandy soils under grass and given large amounts of P fertilizer contained the most labile P and showed the largest P test values. Fallow and reafforestation led to smallest labile P fractions and relative increases of P extractable by H₂SO₄ and residual P. Arable soils with organic and mineral P fertilization given to crop rotations had the largest amounts of total P, labile P fractions and P test values. The mean annual concentrations of P in the lysimeter leachates varied from 0 to 0.81 mg l^–1 (mean 0.16 mg l^–1) and the corresponding leaching losses of P from < 0.01 to 3.2 kg ha^–1 year^–1 (mean 0.3 kg P ha^–1 year^–1). These two sets of data were correlated and a significant exponential function (R² = 0.676) described this relation. Different soil textures, land uses and management practices resulted in similar values for P leaching losses as those for the amounts of labile P fractions. Surprisingly, larger rates of mineral P fertilizer did not necessarily result in greater leaching losses. The contents of P extracted by NaHCO₃ and acid oxalate and the degrees of P saturation were positively correlated with the concentrations of P in leachates and leaching losses. As the P sorption capacity and degree of P saturation predicted leaching losses of P better than did routinely determined soil P tests, they possibly can be developed as novel P tests that meet the requirements of plant nutrition and of water protection.     

Response of phosphorus fractions to land-use change followed by long-term fertilization in a sub-alpine humid soil of Qinghai–Tibet plateau

Purpose

Identification of phosphorus (P) species is essential to understand the transformation and availability of P in soil. However, P species as affected by land use change along with fertilization has received little attention in a sub-alpine humid soil of Tibet plateau.

Materials and methods

In this study, we investigated the changes in P species using Hedley sequential fractionation and liquid-state ³¹P-NMR spectroscopy in soils under meadow (M) and under cropland with (CF) or without (CNF) long-term fertilization for 26 years in a sub-alpine cold-humid region in Qinghai–Tibet plateau.

Results and discussion

Land-use change and long-term fertilization affected the status and fractions of P. A strong mineralization of organic P (OP) was induced by losing protection of soil organic matter (SOM) and Fe and Al oxides during land-use change and resulted in an increase of orthophosphate (from 56.49 mg kg^?1 in M soils to 130.07 mg kg^?1 in CNF soils) and great decreases of orthophosphate diesters (diester-P, from 23.35 mg kg^?1 in M soils to 10.68 mg kg^?1 in CNF soils) and monoesters (from 336.04 mg kg^?1 in M soils to 73.26 mg kg^?1 in CNF soils). Long-term fertilization boosted P supply but failed to reclaim soil diester-P (from 10.68 mg kg^?1 in CNF soils to 7.79 mg kg^?1 in CF soils). This may be due to the fragile protection from the combination of SOM with diester-P when long-term fertilization had only improved SOM in a slight extent.

Conclusions

These results suggest that SOM plays an important role in the soil P cycling and prevents OP mineralization and losses from soil. It is recommended that optimization of soil nutrient management integrated with SOM was required to improve the P use efficiency for the development of sustainable agriculture.

     

Decreased glomalin-related soil protein with nitrogen deposition in a 3-year-old Cunninghamia lanceolata plantation

Purpose

Glomalin-related soil protein (GRSP) is an essential component of soil organic C for maintaining soil quality and structure and plays a critical role in soil carbon (C) sequestration. However, how GRSP changes under nitrogen (N) deposition remains poorly understood.

Materials and methods

We assessed total GRSP (T-GRSP) and easily extractable GRSP (EE-GRSP) under a control (no N input), low N addition (LN, 40 kg N ha^?1 year^?1), and high N addition (HN, 80 kg N ha^?1 year^?1) treatments in 2015 and 2016 in a Chinese fir (Cunninghamia lanceolata) plantation in the subtropical China. We also analyzed soil properties contents and explored the stoichiometric ratios of soil organic C (SOC), total N (TN), and total phosphorus (TP) with GRSPs.

Results

Compared to the control, both T-GRSP and EE-GRSP were significantly reduced under the HN treatment, but had no significant difference under the LN treatment. The ratio of T-GRSP and EE-GRSP was reduced by the N addition. Soil organic C (SOC) and dissolved organic C (DOC) were significantly affected by N addition treatments. The ratios of GRSP-C to SOC and of EEGRSP-C to SOC ranged from 6.29 to 16.07% and 1.34 to 3.52%, respectively. T-GRSP and EE-GRSP were positively correlated with SOC/TN ratio, but negatively correlated with soil TN/TP and SOC/TP ratios.

Conclusion

Our results indicated that the GRSP reductions under N deposition in soil are mediated by soil C, N, and P stoichiometry, and particularly, the reduction of EE-GRSP by DOC. This study improved our mechanistic understanding of dynamics of GRSPs under increasing N enrichment in subtropical plantation ecosystems.

     

Assessing the immobilization efficiency of organic and inorganic amendments for cadmium phytoavailability to wheat

Purpose

Rapid industrialization in China accelerated environmental pollution by xenophores and trace metals particularly cadmium. Numerous studies have been conducted to address soil contamination using organic and inorganic amendments under pot or incubation conditions, but few were performed under field conditions, particularly in the wheat-growing areas. This study aims to investigate the effectiveness of pre-applied soil amendments for Cd immobilization, changes in soil pH, and metal uptake by wheat.

Materials and methods

In this study, 12 treatments, i.e., control (CK), lime, DaSan Yuan (DASY), DiKang No. 1 (DEK1), biochar, Fe-biochar, Yirang, CaMgP, and green stabilizing agents (GSA-1, GSA-2, GSA-3, and GSA-4), were evaluated for Cd immobilization in incubation and field experiments. Changes in soil pH and available metal content with amendments were monitored from 30 to 150 days of incubation. Single extraction method and DTPA-extractable and sequential extraction procedures were employed to assess the variations in available Cd contents of field soil. The impact of soil amendments on Cd uptake and bioaccumulation in food part of wheat was measured at harvesting stage in a contaminated site.

Results and discussion

Lime treatment increased soil pH by 32% and reduced available Cd to 0.213 mg kg^?1, as compared to CK (control) in the incubation experiment (0.343 mg kg^?1). Effects of the amendments on wheat growth, soil pH, and Cd phytoavailability were reported. Wheat biomass was highest in treatment GSA-2 (13,880 kg ha^?1) and GAS-4 resulted in an increase in grain yield (5350 kg ha^?1). Soil pH of the treated field at harvesting stage increased up to 6.50, 6.50, and 6.47 by application of GSA-4, GSA-2, and lime, respectively. Cadmium contents in wheat grain were declined significantly in the treatments of GSA-2, GSA-4, and lime.

Conclusions

Results of this study revealed a significant decrease in available Cd concentration with the application of amendments. Composite amendments were more effective in terms of metal uptake and bioaccumulation in wheat. In addition, our results indicate the effectiveness of composite amendments in stabilizing Cd in contaminated soil.

     

Controllability of Phosphorus Losses in Surface Runoff from Sloping Farmland Treated by Agricultural Practices

Phosphorus (P) loss from arable sloping land due to water erosion causes off‐site environment pollution in the Three Gorges area in China. This study aims to estimate the effects of agricultural practices on the reduction of P losses during water erosion processes under natural precipitation conditions: contour culturing with organic matter addition (CT + OM), contour culturing with wheat straw mulching (CT + SM), contour culturing with straw mulching and organic matter addition (CT + OM + SM) and conventional downslope culturing framework as a control (CK). Results demonstrated that CT + OM + SM could viably diminish runoff, sediment yields and P losses from arable sloping land. Compared with CK, CT + OM, CT + SM and CT + OM + SM lessened the surface runoff depths by 19%, 34% and 50%, respectively. A high curve number value induced a notable runoff potential from the plot. The surface‐runoff‐related total P (TP) loads for CK with yearly measures of 1·56 kg ha⁻¹ were significantly higher than those for CT + OM, CT + SM and CT + OM + SM at 1·07, 0·77 and 0·51 kg ha⁻¹ (p  < 0·05), respectively. With all things considered, the particulate P losses represented a significant division of TP losses, adding up to almost 80% in 2014 and 79% in 2015. The outcomes demonstrated that surface protection and organic matter addition are two of the greatest agricultural protection practices that lessen P losses in the surface runoff from sloping farmland by water erosion. Copyright © 2017 John Wiley & Sons, Ltd.     

Nitrogen losses from outdoor pig farming systems

Abstract. Nitrogen losses via nitrate leaching, ammonia volatilization and nitrous oxide emissions were measured from contrasting outdoor pig farming systems in a two year field study. Four 1‐ha paddocks representing three outdoor pig management systems and an arable control were established on a sandy loam soil in Berkshire, UK. The pig management systems represented: (i) current commercial practice (CCP) ‐ 25 dry sows ha^?1 on arable stubble; (ii) ‘improved’ management practice (IMP) ‐ 18 dry sows ha^?1 on stubble undersown with grass, and (iii) ‘best’ management practice (BMP) 12 dry sows ha^?1 on established grass. Nitrogen (N) inputs in the feed were measured and N offtakes in the pig meat estimated to calculate a nitrogen balance for each system. In the first winter, mean nitrate‐N concentrations in drainage water from the CCP, IMP, BMP and arable paddocks were 28, 25, 8 and 10 mg NO₃ l^?1, respectively. On the BMP system, leaching losses were limited by the grass cover, but this was destroyed by the pigs before the start of the second drainage season. In the second winter, mean concentrations increased to 111, 106 and 105 mg NO₃‐N l^?1 from the CCP, IMP and BMP systems, respectively, compared to only 32 mg NO₃‐N l^?1 on the arable paddock. Ammonia (NH₃) volatilization measurements indicated that losses from outdoor dry sows were in the region of 11 g NH₃‐N sow^?1 day^?1. Urine patches were identified as the major source of nitrous oxide (N₂O) emissions, with N₂O‐N losses estimated at less than 1% of the total N excreted. The nitrogen balance calculations indicated that N inputs to all the outdoor pig systems greatly exceeded N offtakes plus N losses, with estimated N surpluses on the CCP, IMP and BMP systems after 2 years of stocking at 576, 398 and 264 kg N ha^?1, respectively, compared with 27 kg N ha^?1 on the arable control. These large N surpluses are likely to exacerbate nitrate leaching losses in following seasons and make a contribution to the N requirement of future crops.     

Effects of fertilizer type and rate on summer maize grain yield and ammonia volatilization loss in northern China

Purpose

In this study, we analyzed the effects of different maize varieties with nitrogen utilization efficiency, fertilizer type, and rate on the ammonia volatilization emission of farmland. Aimed to seek the best matching method to improve grain yield and fertilizer utilization efficiency of summer maize simultaneously.

Materials and methods

In field experiments, we choose two maize varieties with different nitrogen utilization efficiency (Zhengdan958, Z and Lainong14, L) as material. Set four different fertilizer treatments (200 kg N hm^?2 inorganic fertilizer (U1), 100 kg N hm^?2 inorganic fertilizer (U2), 200 kg N hm^?2 organic fertilizer (M1), and 100 kg N hm^?2 organic fertilizer (M2) to study their effect on NH₃ emission and loss, maize grain yield, and nitrogen accumulation.

Results and discussion

Ammonia volatilization accounted for 8.61–21.68% of applied N. Under the same variety, ammonia volatilization accumulation after fertilization was as follows: U1 > U2 > M1 > M2. Ammonia volatilization rates increased first and then gradually decreased after the fertilization. The ammonia volatilization loss and cumulative loss increased due to increased nitrogen fertilizer application rate. The average nitrogen accumulation and harvest index of 200 kg N hm^?2 N treatments were higher than 100 kg N hm^?2 N treatments, and the difference between the inorganic fertilizer and organic fertilizer was not significant. In 2016 and 2017, the average yield of Zhengdan958 was 11,758.79 kg hm^?2, which was 15.78% higher than that of Lainong14, and the difference between the two fertilizer types was not significant. The average yield of 200 kg N hm^?2 N treatment was 11,959.42 kg hm^?2, which was 20.13% higher than those of 100 kg N hm^?2 N treatment.

Conclusions

By changing the type of fertilizer, replacing chemical fertilizers with organic fertilizer can reduce the loss of ammonia volatilization and promote the synergistic improvement to yield and resource utilization efficiency. Among them, using nitrogen-efficient varieties and using organic fertilizer instead of chemical fertilizer was beneficial to reduce the loss of ammonia volatilization, increase the accumulation of nitrogen, and promote the growth of maize to obtain high yield.

     

Eucalyptus biochar application enhances Ca uptake of upland rice,soil available P,exchangeable K,yield, and N use efficiency of sugarcane in a crop rotation system

It was hypothesized that the application of eucalyptus biochar enhances nutrient use efficiencies of simultaneously supplied fertilizer, as well as provides additional nutrients (i.e., Ca, P, and K), to support crop performance and residual effects on subsequent crops in a degraded sandy soil. To test this hypothesis, we conducted an on‐farm field experiment in the Khon Kaen province of Northeastern Thailand to assess the effects of different application rates of eucalyptus biochar in combination with mineral fertilizers to upland rice and a succeeding crop of sugarcane on a sandy soil. The field experiment consisted of three treatments: (1) no biochar; (2) 3.1 Mg ha^?1 biochar (10.4 kg N ha^?1, 3.1 kg P ha^?1, 11.0 kg K ha^?1, and 17.7 kg Ca ha^?1); (3) 6.2 Mg ha^?1 biochar (20.8 kg N ha^?1, 6.2 kg P ha^?1, 22.0 kg K ha^?1, and 35.4 kg Ca ha^?1). All treatments received the same recommended fertilizer rate (32 kg N ha^?1, 14 kg P ha^?1, and 16 kg K ha^?1 for upland rice; 119 kg N ha^?1, 21 kg P ha^?1, and 39 kg K ha^?1 for sugarcane). At crop harvests, yield and nutrient contents and nitrogen (N) use efficiency were determined, and soil chemical properties and pH₀ monitored. The eucalyptus biochar material increased soil Ca availability (117 ± 28 and 116 ± 7 mg kg^?1 with 3.1 and 6.2 Mg ha^?1 biochar application, respectively) compared to 71 ± 13 mg kg^?1 without biochar application, thus promoting Ca uptake and total plant biomass in upland rice. Moreover, the higher rate of eucalyptus biochar improved CEC, organic matter, available P, and exchangeable K at succeeding sugarcane harvest. Additionally, 6.2 Mg ha^?1 biochar significantly increased sugarcane yield (41%) and N uptake (70%), thus enhancing N use efficiency (118%) by higher P (96%) and K (128%) uptake, although the sugar content was not increased. Hence, the application rate of 6.2 Mg ha^?1 eucalyptus biochar could become a potential practice to enhance not only the nutrient status of crops and soils, but also crop productivity within an upland rice–sugarcane rotation system established on tropical low fertility sandy soils.