Plant-available Soil Research Articles

Extractable soil silicon in relation to sugarcane yield on mineral soil

Florida sugarcane production is mostly on organic soils, but the cultivation area on mineral soils is also expanding. Silicon (Si) is beneficial for sugarcane growth and development on weathered soil. However, the low solubility and availability of soluble Si is an issue in Florida’s mineral soils. This study aimed to assess soil Si extraction methods based on sugarcane yield response to calcium silicate application. It also examined the relationship between sugarcane yield with extracted plant-available soil Si, alongside plant Si concentrations. The experiment followed a randomized complete block design involving 2 fields, with 24 plots each, and 6 replications. Four rates of calcium silicate (0 control, 2.24, 4.48, and 6.67 Mg ha−1) were applied before planting sugarcane. Soil samples were collected prior to planting and after each harvest. Soil Si was extracted using 0.5 M acetic acid, 0.7 N NH4OAc, Mehlich 3, and 0.01 M CaCl2 extractants. Leaf samples were collected over a three-year sugarcane life cycle (from 2019 to 2022) to evaluate the relationship between soil Si and leaf Si concentrations. The relationships between parameters were analyzed using linear and nonlinear regression models. Results indicated that higher Si application rates increased Si concentrations in sugarcane leaves in both fields. However, only one field showed a yield response to Si, likely due to high pre-plant soil Si in the other field. The best extractant should correlate strongly with either yield or leaf Si content, but no single extractant showed a strong correlation with either, making it infeasible to identify the best extractant.

Phosphorus High-rate application through band placement improved cotton productivity under arid climate

The plant-available soil phosphorus rate and methods for applying phosphatic fertilizer and soil P-fixation capacity are critical factors for lower cotton productivity in Southern Punjab, Pakistan. Hence, a two-year study was conducted in Central Cotton Research Institute (CCRI), Multan, Pakistan, to examine the effects of various P rates and application methods on cotton crop output during the growing seasons of 2014 and 2015. Phosphorus was applied in four rates (0, 40, 80, and 120 kg ha−1 P2O5) using broadcast, band application, and fertigation methods. Results indicated that the impact of P rates was statistically significant on plant height, the number of nodes, monopodial and sympodial branches, leaf area index, harvest index, and seed cotton yield. The greater P application (120 kg P2O5 ha−1) had a better effect on cotton productivity than the lower application rates (0, 40, and 80 kg P2O5 ha−1). The band application responded better on nodes plant−1, sympodial branches plant−1, boll weight, leaf area index, lint yield, and harvest during the growing season 2015. Therefore, by adopting the band application coupled with 120 kg P2O5 ha−1 rather than the conventional method of broadcast, productivity of cotton crops could be increased.

Functional and mechanistic assessment of plant-available soil phosphorus greatly improved the multisite diagnosis of maize yield response

Context or problemPlant-available soil phosphorus (P) is commonly assessed by chemical extractions with the purpose of diagnosing and advising fertilizer P application. However, for a given crop, this approach only poorly predicts yields obtained from several experimental sites. To solve this major drawback, a functional and mechanistic evaluation has been developed to mimic dominant processes involved in the absorption of phosphate ions. Objective or research questionIn this study, we investigated the predictive ability of a mechanistic approach to diagnose maize (Zea mays L.) yields, in comparison to the common Olsen's method (0.5 M bicarbonate solution). MethodsThe processes-based assessment consists of parameterizing relationships between amount of diffusible phosphate ions (Pr) at the solid-to-solution interface equilibrating the phosphate ions concentration in solution (CP) with time (t). We parameterized [Pr vs. (CP, t)] relationships for stored and archived soil samples (plough layer) of nine long-term field experiments (LTFEs) on increasing rates of P applications including the zero-P treatment (P0). LTFEs were located in different soils (Luvisol, Podzol, Arenosol, Calcosol) with large variations in physico-chemical properties. We also used LTFEs database of maize yields. ResultsThe CP values ranged from 0.02 to 3.86 mg P L−1 for 40 (LTFE×year of maize cropping) combinations. The (Pr=v×CPw×tp) equation closely described the [Pr vs. (CP, t)] datasets, with (v, w, p) parameters being soil specific. Maximum yields ranged from 5.5 to 14.7 t DM ha−1 depending on LTFEs and years. Yields decreased significantly only in P0, and did not differ for other P rates. The relationship between the relative maize yield and CP was sites-specific with CP thresholds to obtain a relative yield of 0.95 ranged from 0.07 to 0.88 mg P L−1 solution. Taking into account amounts of phosphate ions which balance CP by diffusion using (Pr=v×CPw×tp) equations, a single response curve is observed for the 9 LTFEs when the replenishment time is 1500 minutes (i.e. about one day). The critical CP thresholds closely correlated to the ability of the soil solid phase to buffer phosphate ions in solution. ConclusionsFor the 9 studied LTFEs on P fertilization, the [Pr vs. (CP, t)] relationships were more able to account for maize response curves than P extracted by Olsen method, improving the precision and reliability of the multisite diagnosis of maize yield response. Implications or significanceAs a result, P fertilization recommendations are more reliable regardless of soil type. Further progress could be gained by taking into account for the role of the soil layer beneath the plough layer.

Soil health as a proxy for long-term reclamation success of metal-contaminated mine tailings using lime and biosolids

Mine lands contaminted with heavy metals pose environmental risks, and thus reclamation is paramount for improving soil, plant, animal, and ecosystem health. A metal-contaminated alluvial mine tailing, devoid of vegetation, received 224 ​Mg ​ha−1 of both lime and biosolids in 1998, and long-term reclamation success was quantified in 2019 with respect to soils, plants, and linkages to animals. Reclamation success was quantified using the Soil Management Assessment Framework (SMAF), in conjunction with bioavailable (0.01 ​M CaCl2 extractable) and plant-available (Mehlich-3 extractable) soil metal concentrations, X-ray absorption spectroscopy, plant metal concentrations, and plant quality characteristics. Results showed that all soil indicators were improved in successfully-reclaimed areas as compared to on-site degraded areas, including increases in soil aggregate stability, pH, plant-available P and K, soil organic C, potentially-mineralizable N, microbial biomass C and β-glucosidase activity and decreases in soil bulk density and electrical conductivity. Of indicators, unitless soil health scores were assigned based on the SMAF, with data suggesting that bulk density, wet aggregate stability, potentially- mineralizable N, microbial biomass C, pH, and electrical conductivity should be monitored in the future. The long-term effects of lime and biosolids application have improved soil physical, biological, and overall soil health. Plant metal concentrations have decreased by an order of magnitude since early reclamation, with most plant metal concentrations being tolerable for domestic livestock consumption. From an animal health perspective, feeding grasses from this site during latter parts of a growing season may need supplemental feed to provide greater protein and energy content, and to reduce potentially-harmful Cd concentrations from food chain bioaccumulation. However, a health concern exists based on soil bioavailable Cd and Zn concentrations that exceed ecological soil screening levels. Still, plants have stabilized the soil and acidity remains neutralized, leading to long-term improvements in soil health, with overall improved ecosystem health.

The impact of climate and potassium nutrition on crop yields: Insights from a 30-year Swiss long-term fertilization experiment

Climate change will strongly influence agricultural practices in the future. In order to promote resource-efficient agriculture, it is important to analyse the impact of climate variation on crop yields. In this study, we report yields of spring wheat, winter barley, maize, potato and sugar beet from the long-term crop rotation and fertilization experiment Demo in Switzerland and analyze their response to different climate variables (e.g., annual and seasonal temperature, precipitation, evapotranspiration, number of heat days and days of heavy rainfall). In addition, we investigate the impact of readily plant-available soil potassium (K) on the relationship of crop yields and precipitation. Annual and summer temperatures increased by 1 °C and 1.5 °C, respectively, over the observation period, and both the number of heat days and days of heavy rainfall increased in summer. Rising summer temperatures have a negative impact on all crop yields, which was most prominent for spring wheat, potato and maize. Annual, spring and summer precipitation show varying effects on different crops. For maize, soil K has a mediating effect on yield reductions under low spring precipitation. Yields are significantly reduced by 1 t ha−1 per 100 mm reduction of precipitation below a soil K threshold of 7 mg K kg−1 soil. Based on these results and the future climate scenarios for Switzerland, crop rotations with less heat-sensitive species and early-maturing varieties should be considered. In order to keep future irrigation demands and costs as low as possible, the soil K fertility classes in the Swiss K fertilization guidelines might need to be revisited. Our study is one of a few long-term observations that show the impact of climate variation on crop yields and highlights the potential of K management as a climate change adaptation measure.

Phosphorus applications adjusted to optimal crop yields can help sustain global phosphorus reserves

With the longevity of phosphorus reserves uncertain, distributing phosphorus to meet food production needs is a global challenge. Here we match plant-available soil Olsen phosphorus concentrations to thresholds for optimal productivity of improved grassland and 28 of the world’s most widely grown and valuable crops. We find more land (73%) below optimal production thresholds than above. We calculate that an initial capital application of 56,954 kt could boost soil Olsen phosphorus to their threshold concentrations and that 28,067 kt yr−1 (17,500 kt yr−1 to cropland) could maintain these thresholds. Without additional reserves becoming available, it would take 454 years at the current rate of application (20,500 kt yr−1) to exhaust estimated reserves (2020 value), compared with 531 years at our estimated maintenance rate and 469 years if phosphorus deficits were alleviated. More judicious use of phosphorus fertilizers to account for soil Olsen phosphorus can help achieve optimal production without accelerating the depletion of phosphorus reserves.

Increasing complexity of agroforestry systems benefits nutrient cycling and mineral-associated organic carbon storage, in south-eastern Brazil

Agroforestry systems are often promoted as solutions to address land degradation and climate change. However, agroforestry is an umbrella term for a large variety of systems and it is not clear how their degree of complexity influences their provision of soil-based ecosystem services, such as soil organic carbon (SOC) storage and nutrient cycling. Furthermore, a knowledge gap remains whether agroforestry systems perform equally well on all soil types. The objectives of this study were 1) to assess the links between agroforestry complexity, nutrient cycling and SOC fractions, and 2) to assess how soil texture influences these relationships in Brazilian agroforestry systems. We sampled 59 agroforestry plots across 30 sites in Sao Paulo state, Brazil, and 8 monocrop sites (6 pastures and 2 crop monocultures). The 38 sites represented a soil textural gradient, ranging from very sandy to very clayey (clay content range 25 – 620 g kg−1). An Agroforestry Complexity Index (ACI) was defined based on tree species richness, stem density and pruning management. Nutrient (N, P, K, Ca, Mg) and C contents were determined in litter and soil (0–30 cm depth) samples, and mineral-associated organic C (MAOC) and particulate organic C (POC) in soil samples were assessed as well. ACI was positively associated with C, N, P, Ca and Mg stocks in litter, and these litter nutrients were in turn positively associated with the corresponding soil nutrient stocks. Associations between soil nutrients and MAOC were stronger on sandy soils than on clayey soils, particularly for P, Ca and Cation Exchange Capacity (CEC). For POC, robust relationships with nutrients were only found on sandy soils. Structural Equation Models indicated causal relationships between agroforestry complexity, P and Ca cycling, and MAOC and POC stocks in topsoils. Our results indicate that nutrients effectively cycle from in situ mulch into plant-available soil pools and highlight the synergies between nutrient cycling and stable C stocks that can be achieved in complex agroforestry systems. These synergies seem to be particularly strong on sandy soils (<15 % clay).

Silicon-based anti-herbivore defense in tropical tree seedlings.

Silicon-based defenses deter insect herbivores in many cultivated and wild grass species. Furthermore, in some of these species, silicon (Si) uptake and defense can be induced by herbivory. Tropical trees also take up Si and leaf Si concentrations vary greatly across and within species. As herbivory is a major driver of seedling mortality and niche differentiation of tropical tree species, understanding anti-herbivore defenses is pivotal. Yet, whether silicon is a constitutive and inducible herbivory defense in tropical forest tree species remains unknown. We grew seedlings of eight tropical tree species in a full factorial experiment, including two levels of plant-available soil Si concentrations (-Si/+Si) and a simulated herbivory treatment (-H/+H). The simulated herbivory treatment was a combination of clipping and application of methyl jasmonate. We then carried out multiple-choice feeding trials, separately for each tree species, in which leaves of each treatment combination were offered to a generalist caterpillar (Spodoptera frugiperda). Leaf damage was assessed. Three species showed a significant decrease in leaf damage under high compared to low Si conditions (by up to 72%), consistent with our expectation of Si-based defenses acting in tropical tree species. In one species, leaf damage was increased by increasing soil Si and in four species, no effect of soil Si on leaf damage was observed. Opposite to our expectation of Si uptake and defense being inducible by herbivory damage, simulated herbivory increased leaf damage in two species. Furthermore, simulated herbivory reduced Si concentrations in one species. Our results showed that tropical tree seedlings can be better defended when growing in Si-rich compared to Si-poor soils, and that the effects of Si on plant defense vary strongly across species. Furthermore, Si-based defenses may not be inducible in tropical tree species. Overall, constitutive Si-based defense should be considered part of the vast array of anti-herbivore defenses of tropical tree species. Our finding that Si-based defenses are highly species-specific combined with the fact that herbivory is a major driver of mortality in tropical tree seedling, suggests that variation in soil Si concentrations may have pervasive consequences for regeneration and performance across tropical tree species.

Integrative application of biochar and arbuscular mycorrhizal fungi for enhanced chromium resistance in Medicago sativa

Soil chromium (Cr) contamination has become an environmental problem of global concern. However, the joint effects of combined utilization of biochar and arbuscular mycorrhizal (AM) fungal inoculum, which are considered as two promising remediation strategies of soil heavy metal pollutions, on plant Cr resistance are still poorly understood. In this study, a two-factor pot experiment was conducted to investigate how biochar and AM fungus Rhizophagus irregularis regulate Medicago sativa growth, physiological trait, nutrient and Cr uptake, relevant gene expressions, soil properties, and Cr speciation, independently or synergistically. The results showed that biochar notably decreased AM colonization, while biochar and AM fungus could simultaneously increase plant dry biomass. The greatest growth promotion was observed in mycorrhizal shoots at the highest biochar level (50 g kg−1 soil) by 91 times. Both biochar application and AM fungal inoculation enhanced plant photosynthesis and P nutrition, but the promoting effects of AM fungus on them were significantly greater than that of biochar. In addition, the combined application of biochar and AM fungus dramatically reduced shoot and root Cr concentrations by up to 92 % and 78 %, respectively, compared to the non-amended treatment. Meanwhile, down-regulated expressions were observed for metal chelating-related genes. Furthermore, Cr translocation from roots to shoots was reduced by both two soil amendments. Transcriptional levels of genes involved in reactive oxygen species and proline metabolisms were also regulated by biochar application and AM fungal colonization, leading to alleviation of Cr phytotoxicity. Furthermore, AM fungal inoculation slightly elevated soil pH but decreased plant-available soil P, which was, by contrast, lifted by biochar addition. The combined application reduced soil acid-extractable Cr concentration by 40 %. This study provides new insights into comprehensively understanding of the mechanisms of biochar and AM fungi combination on improving plant Cr tolerance.

Tillage, Manure, and Biochar Short-Term Effects on Soil Characteristics in Forage Systems

Manure, a globally used soil amendment, can contribute to excessive N and P runoff, leading to water pollution. Biochar (BC) shows promise in mitigating nutrient loss by retaining soil nutrients. However, there is limited research exploring the combined effects of tillage practices, biochar, manure, forage crops, and soil types on soil nutrient characteristics in a single field study. Our objectives are to determine if, in North Central Texas, differing soil types, soil amendments, forage crops, and tillage practices affect soil nutrients when applied short term, and whether correlations exist among soil nutrient characteristics as affected by soil amendments, tillage practices, and the presence of forage crops. The study encompasses three field sites with five factors, including soil types, manure rates, biochar rates, tillage practices, and forage crop types. Soil samples were assayed for pH, electrical conductivity (EC), macronutrients, and micronutrients. Data analyses involved variance analysis, Fisher’s tests, and Pearson’s correlations using R in Rstudio (the IDE). Microplots treated with manure (average 2.16 ppm) retained 60% greater average nitrate levels at the end of the growing season than those treated with a synthetic fertilizer (average 1.35 ppm) (p ≤ 0.05). Moderate and strong correlations were observed between EC and S (r (106) = 0.43, p &lt; 0.001 in loamy sand soil; r (106) = 0.80, p &lt; 0.001 in clay loam soil) and between nitrate and Zn, (r (106) = 0.36, p &lt; 0.001 in loamy sand soil; r (106) = 0.44, p &lt; 0.001 in sandy loam soil) across different soil types. Soil type (texture) emerged as the primary influencing factor on plant-available soil nutrients and characteristics, followed by manure application and tillage practices. The impact of BC and forage crop type varied depending on other experimental factors. Understanding the influence of soil type, amendment application, and tillage on soil nutrient characteristics can guide sustainable forage production practices and soil nutrient management strategies.

Nitrous oxide emissions after struvite application in relation to soil P status

PurposeAlthough struvite (MgNH4PO4·6H2O) is mostly considered to be a novel phosphorus (P) fertiliser, it does contain a significant amount of nitrogen (N). Yet, relatively little is known about the soil N dynamics in struvite-amended soils. Here, we focus on how struvite application impacts emissions of the greenhouse gas nitrous oxide (N2O), in relation to soil P status.MethodsWe conducted a 54-day greenhouse pot experiment on two similar soils with different P status (“low-P soil”; “high-P soil”) seeded with Lolium perenne L. We applied seven fertiliser treatments (Control; Struvite granules; Struvite powder; Urea; Triple superphosphate (TSP); TSP + Struvite granule; TSP + Urea). Except for the unfertilised Control and the TSP treatments, N application rate was 150 kg N‧ha−1. Nitrous oxide (N2O) fluxes, aboveground yield, plant N and P uptake and readily plant-available soil N and P contents were measured.ResultsIn the low-P soil, none of the fertiliser treatments induced a significant increase in N2O emission compared to the control. In the high-P soil, struvite application resulted in lower emissions than urea application, statistically not different from the control treatment. Struvite powder significantly increased both plant N and P uptake compared to granular struvite and the resulting yield was similar to conventional fertilisation (TSP and Urea). Any struvite application also resulted in lower readily plant-available soil nitrate contents than urea.ConclusionOur results suggest that struvite fertilisation can reduce the risk of gaseous N losses without compromising agronomic performance. Pulverizing struvite granules further promotes its dissolution, which could be useful for crops with early nutrient needs.

Dynamics of root–microbe interactions governing crop phosphorus acquisition after straw amendment

Phosphorus (P) mobilization by microorganisms influences root morphological and exudation traits related to crop nutrient acquisition. However, the dynamics of root P acquisition strategies in response to P immobilization followed by release that accompany microbial growth and decay remain unclear. We evaluated root–microbe interactions governing P uptake by Brassica chinensis and Solanum lycopersicum grown for 56 days in low-P (10 mg P kg−1) and high-P (100 mg P kg−1) soil with or without straw addition. Straw addition increased the growth of bacteria and fungi (including microorganisms harbouring the phoD, phoC and pqqC genes) and enhanced the microbial P pool. The high microbial abundance 29 days after straw addition was associated with short roots and weak carboxylate exudation in B. chinensis and S. lycopersicum regardless of P fertilization. Phosphate-solubilizing microbes harbouring the phoD, phoC and pqqC genes together with microbial P release increased plant-available soil P, influencing variation in root P-acquisition strategies between the species. The high level of CaCl2-extractable P due to P release upon microbial decay and phosphate-solubilizing microorganisms was associated with short roots and weak carboxylate exudation in B. chinensis, but underpinned crop nutrient acquisition in low-P soil amended with straw after day 40. S. lycopersicum increased root elongation in response to mobilization of microbial P after day 44. The long roots coupled with the increased P availability due to microbial P release elicited large P acquisition by S. lycopersicum in straw-amended, low-P soil. By contrast, microbial abundance and microbially mediated P availability had little influence on root P-acquisition strategies in B. chinensis and S. lycopersicum in high-P, straw-amended soil. This study highlighted the importance of temporally varying root–microbe interactions in influencing crop P acquisition in low-P, straw-amended soil.

Soil zinc deficiency and child stunting: Evidence from Nepal

We examine the negative child health impacts of soil zinc (Zn) deficiency in Nepal. Soil Zn deficiency limits both crop yields and the Zn concentration in food crops, leading many to speculate that it underlies human Zn deficiency and child stunting, globally and particularly in South Asia. We find strong evidence that soil Zn deficiency does have a causal impact on child stunting in Nepal’s Tarai region, the breadbasket of the country. Using causal bounds, we find that a 1 part per million increase in plant-available soil Zn – achievable with application of Zn-enriched fertilizer – decreases child stunting by between 1 and 7.5 percentage points. Multiple statistical sensitivity tests indicate that this relationship is unlikely to be manufactured by omitted, relevant variables.

Increased microbial biomass and turnover underpin efficient phosphorus acquisition by Brassica chinensis

Root-microbe interactions are critical in influencing crop productivity. Microbial phosphorus (P) mobilization in soil determines P availability to plants, but how plants modify root acquisition strategies in response to microbially mediated P availability remains unknown. We conducted a pot experiment with rice straw addition to investigate effects of microbial P on plant-available soil P (CaCl2-P and NaHCO3-P) as well as root morphological and exudation traits related to P acquisition in Brassica chinensis. Microbial P immobilization caused by straw addition decreased plant-available P in soil and induced growth of short and thick roots at day 21. In parallel with decline in microbial P in straw-amended soil from the 21st to 42nd day, B. chinensis stimulated root elongation to get close to length of roots without straw. Rhizosphere carboxylate exudation by B. chinensis was greater by seven-fold in the treatment with than without straw at day 42. Field experiments with five successive B. chinensis crops were used to test whether root-microbe interactions can be manipulated by straw amendment to increase crop P uptake and yield. Phosphorus uptake by the first three successive B. chinensis crops was similar with or without straw addition. However, further repeated straw addition increased soil microbial P pool by one-fold and quantity of phosphate-solubilizing bacterial phoD gene by fifty-eight percent, after the 4th compared with those after the 2nd crop. Phosphorus released from microbial biomass turnover underpinned growth of roots with large specific length and low tissue density that are highly efficient in P acquisition, resulting in increased shoot P accumulation and yield in the 4th and 5th B. chinensis crops. In summary, crops shift root strategies from the P-conservative towards P-acquisitive traits in response to microbial biomass turnover. Straw amendment can facilitate root-microbe interactions governing sustained P availability and effective root P-acquisition strategies, thus increasing P-use efficiency.

Global maps of potential and climatic plant-available soil water

Global maps of potential and climatic plant-available soil water

Global maps of potential and climatic plant-available soil water

Global maps of potential and climatic plant-available soil water

Leaf trait modification in European beech trees in response to climatic and edaphic drought.

Leaf morphological and physiological traits control the carbon and water relations of mature trees and are determinants of drought tolerance, but it is not well understood how they are modified in response to water deficits. We analysed five sun-canopy leaf traits (mean leaf size (LS), specific leaf area (SLA), Huber value (HV), water potential at turgor loss point (Ψtlp ) and foliar carbon isotope signature (δ13 C)) in European beech (Fagus sylvatica L.) across three precipitation gradients sampled in moist (2010), dry (2019) and very dry (2018) summers, and tested their response to short-term water deficits (climatic water balance (CWB) preceding sample collection) and long-term water availability (mean annual precipitation (MAP), plant-available soil water capacity (AWC) and neighbourhood competition). Across the 34 sites, LS varied seven-fold (3.9-27.0 cm2 ), SLA four-fold (77.1-306.9 cm²·g-1 ) and HV six-fold (1.0-6.65 cm2 ·m-2 ). In the 2018 dataset, LS showed a negative and HV a positive relationship to MAP, which contradicts relations found in multi-species samples. Average Ψtlp ranged from -1.90 to -2.62 MPa and decreased across the sites with decreasing CWB in the month prior to measurement, as well as with decreasing MAP and AWC in 2019. Studied leaf traits varied considerably between years, suggesting that mast fruiting and the severe 2018 drought caused the formation of smaller leaves. We conclude that sun-canopy leaf traits of European beech exhibit considerable plasticity in response to climatic and edaphic aridity, and that osmotic adjustment may be an important element in the drought response strategy of this anisohydric tree species.

Cover Crop Effects on Cash Crops in Northern Great Plains No-till Systems Are Annually Variable and Possibly Delayed

ABSTRACT Cover crop adoption in conventional no-tillage corn/soybean production systems has been limited due to the lack of specific information regarding the impact of cover crops on cash crop performance. Within a no-till small grain/cover crop-corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation in eastern South Dakota, we evaluated the impact of fall-planted forage oat (Avena sativa L.), hairy vetch (Vicia villosa Roth), winter canola (Brassica napus L.), and a combination of all three compared to a no cover crop treatment on soil nutrient dynamics, biomass, nutrient uptake, and grain yield of the immediatelyfollowing corn crop. At site-year 1, where cover crop growth was most consistent, corn yield was significantly higher with oat, vetch, and a combination of all three cover crops compared to the no cover crop treatment. At site-year 2, corn yields were equivalent among treatments except the combination treatment which was significantly lower. At site-year 3, corn yields in the canola and oat treatments were equivalent to no cover crop, while corn yields with vetch and the combination treatments were lower. Corn biomass and nutrient uptake responded to treatments similarly to corn yields. For site-years 1 and 2, some cover crop treatments resulted in modest, but significant increases in soil N during spring. For site-year 3, the combination treatment immobilized N during the corn vegetative growth phase but released N during the reproductive phase. Cover crop treatments had little effect on plant-available soil P. However, soybean yields two years following cover crop treatments were higher for all three site years with cover crops compared to no cover crop, with this difference significant in two of the three site-years. Immediate effects of cover crops on the following cash crop under no-till were variable and depend on both fall and spring cover crop biomass, which in turn are dependent on the amount and timing of precipitation and temperature patterns. Cover crops in no-till systems may produce more consistent but possibly delayed benefits by boosting yields of cash crops in later years as cover crop residues decompose.

Regional variations in plant-available soil water storage and related driving factors in the middle reaches of the Yellow River Basin, China

Available soil water is considered the most important water resource for food production in agricultural ecosystems and sustainable vegetation restoration in arid and semi-arid regions. Compared to soil water content, plant-available soil water storage (ASWS) directly indicates the amount of soil water that can be used by plants. Understanding the spatial characteristics and controlling factors of ASWS can aid in improving the ability of the agricultural ecosystem to resist extreme natural disasters and stabilise grain production in China. In this study, ASWS in the 0–5.0 m profile was measured in an area of approximately 36.9 × 104 km2 in the middle reaches of the Yellow River Basin. The total ASWS in the 0–5.0 m profile of the study area was 113 × 1010 m3, 85% of which was stored in the > 450 mm rainfall zones. The spatial variation in ASWS was mainly controlled by climate and edaphic properties of the 0–1.0 m soil layer and < 450 mm rainfall zone. Regarding the 1.0–5.0 m soil layer and > 450 mm rainfall zone, edaphic properties were the dominant factors determining the spatial characteristics of ASWS. Based on the spatial characteristics of ASWS, the shallow soil water (0–1.0 m) in the middle region and deep soil moisture (1.0–5.0 m) in the southern region of the study area can support the rational use of soil water in agricultural and vegetation restoration activities. Large-scale revegetation activities using trees or shrubs might not be the optimal choice in regions with mean annual precipitation < 450 mm. Knowledge of the spatial characteristics and contributions of the ASWS controlling factors is indispensable for reasonable agricultural regionalisation and vegetation restoration, as well as for an invulnerable and stable grain output system.

Impact of manure and biochar additions on annual crop growth, nutrient uptake, and fate of 15N-labelled fertilizer in two contrasting temperate prairie soils after four years

Liquid hog manure (LHM) and solid cattle manure (SCM) co-applied with biochar could beneficially influence soil nitrogen (N) and phosphorus (P) dynamics. A split-plot design was used at two sites (Brown and Black) in Saskatchewan to assess LHM and SCM (100 kg N·ha−1) applied alone or in combination with biochars (8 Mg carbon·ha−1) produced using slow or fast pyrolysis. Crop growth and nutrient uptake, along with fertilizer 15N recovery, were followed over four years in a cereal–oilseed rotation. Crop growth on the Brown soil was more responsive to the treatments than the Black soil, reflecting lower fertility of the Brown soil. The manure and biochar, applied alone or in combination, had little impact on available soil P. Manure and biochar effects on crop growth and nutrient uptake were attributed to temporal effects on soil N immobilization–mineralization influencing plant-available soil N. A negative impact of the fast pyrolysis biochar on growth and plant uptake was observed and attributable to its greater labile-carbon content, which likely promoted soil N immobilization. Synergism observed between SCM and the slow pyrolysis biochar may reflect enhanced net SCM-N mineralization and increased water-holding capacity. The majority (55%–80%) of plant 15N recovery occurred during the first year, with 86% of fertilizer 15N conserved within the soil–plant system after four years. Greater (40%) plant 15N recovery without biochar addition, coupled with increased (38%) soil 15N recovery with added biochar, suggests biochar-related immobilization and (or) sorption in the biochar-amended soils.