Unfertilized Treatment Research Articles

Animal manure digestate fertilization effect on the soil microbial activity and crop productivity in the northern part of temperate climate conditions-Lithuania

Microbial communities make up a significant portion of the soil, and their activity is crucial to the soil's ability to function. In this study, we aim to evaluate the influence of animal waste-based digestate as N source on soil microbial activity and crop productivity over a three-year period in a crop rotation system. Two experimental field trials using the same design were performed in the year 2018–2020 and 2019–2021, respectively. Four different fertilization treatments, namely Synthetic Nitrogen, Chicken manure digestate, Cow manure digestate, and Pig manure digestate split fertilized (90 kg ha−1 N and 80 kg ha−1 N), and unfertilized treatment (control) were studied while growing different annual crops (spring wheat, triticale, and barley). There was a more significant positive effect on the soil microbial biomass carbon noticeably observed after the first year of digestate application, with an increase of 20.2–75% when compared to the unamended soil. Soil dehydrogenase activity was a less sensitive indicator for the effect of fertilization on soil biochemical activity, but the average data from both experiments showed an increase in fertilized soils from 6.6 to 8.5% in fertilized soils. The soil moisture did not significantly influence the microbial biomass and the enzymatic activity. However, crop productivity consistently rose each successive year, a positive effect of digestate use. We deduced that the long-term application of animal manure digestate under natural conditions coupled with other variable factors such as seasonal conditions and agricultural management techniques significantly influenced the microbial biomass contents – a critical component of the biological state of the soil. Our findings will help identify how and what could make soil microbial communities and crop productivity vulnerable to seasonal changes in relation to the consistent application of animal manure digestate to agricultural soils and the agricultural techniques employed.

Exploring Phosphorus Fraction Dynamics in Loess Soils: Impact of Long-Term Nitrogen and Phosphorus Fertilization on Cropland and Fallow Land

Long-term cropping systems require balanced phosphorus (P) management for better yield and environmental sustainability. However, the soil P transformations under fallow rotations with and without long-term nitrogen (N) and P fertilization largely remained unknown. This study evaluated the status of P forms in loess soils in response to varied combined rates of N and P fertilizers, tillage management practices, fallow land systems (natural fallow (NF), and bare fallow (BF)). Four NP treatments (N0P0, control; N0P100, 100 kg P ha−1; N160P0, 160 kg N ha−1; and N160P100), and two treatments with no fertilizer application and crops (NF and BF) were conducted. The treatments N0P100 and N160P100 significantly increased soil total P, inorganic P (Pi), organic P (Po), and Olsen P concentrations compared to the control, NF, and BF treatments. Labile P fractions (NaHCO3-Po and NaHCO3-Pi) were 7.30% and 11.8–12.4% higher in fertilized treatments than in control, NF, and BF treatments. The moderately labile NaOH-Pi was stable in all treatments, but NaOH-Po significantly decreased in the NF (2.60%) and BF (1.40%) treatments compared to the control and fertilized treatments; however, HClD-Pi was 59.1–66.0% higher in NF and BF compared to the control and fertilized treatments. Non-labile P (HClC-Pi and HClc-Po) fractions showed no significant difference between the fertilized and unfertilized treatments. Residual P levels were substantially greater in the P fertilized (N0P100) treatment than in the fallow treatments. The conceptual framework and redundancy (RDA) analysis revealed that the labile (NaHCO3-Pi and NaHCO3-Po) and moderately labile P fractions (NaOH-Po, NaOH-Pi, and HClD-Pi) were substantially associated with Olsen P contents, grain yield, and P uptake. Higher moderate fraction concentrations in fallows and their positive correlation with yield, P uptake, and Olsen P predict the importance of reserved P in these soils upon long-term fertilization, suggesting the utilization of P legacy and optimizing fertilizer applications.

Nitrogen dynamics after slurry application as affected by anaerobic digestion, biochar and a nitrification inhibitor

AbstractAnimal manures are valuable multi‐nutrient fertilizers, but their short‐term nitrogen (N) use efficiency (NUE) by plants is low, bearing the potential of harmful N losses to the environment, such as nitrate () leaching. To develop strategies to increase the NUE of cattle slurry, a comprehensive understanding of slurry N dynamics in the soil–plant system is needed. In a 57‐day microcosm experiment in the greenhouse, we assessed the effect of different slurry treatments on slurry N turnover in the soil and its uptake by ryegrass (Lolium multiflorum var. Westerwoldicum). Employing a two‐factorial design, 15N cattle slurry (SLU), 15N anaerobically digested cattle slurry (SLA), and 15N anaerobically digested cattle slurry plus biochar (SLA+) were combined with and without the nitrification inhibitor 3,4‐dimethyl‐1H‐pyrazole monophosphate (DMPP). As references, a mineral fertilizer (MIN) and an unfertilised treatment (N0) were included. The 15N recovery, hence NUE, in plant biomass was higher for SLA than for SLU, while recovery in soil at 55 days after set‐up showed an opposite trend, with over 45% of N from SLU still being recovered in soil. DMPP and biochar only marginally affected NUE and fertilizer N recovery in soil. Although 15N recovery in soil was highest for SLU, residual N leaching from SLU was low (<1% of added N). We attribute this to the limited presence of slurry N in mineral forms at this point of time, with the majority being stored in the non‐microbial organic soil N pool. Leaching of residual N from MIN was significantly higher for MIN than for SLU, while SLA and SLA+ ranged in between. Overall, anaerobic digestion appeared suitable for increasing NUE of cattle slurry, but further investigations under field conditions are necessary in order to assess its potential to reduce nitrate leaching in the long‐term.

Host plant height explains the effect of nitrogen enrichment on arbuscular mycorrhizal fungal communities.

Nitrogen (N) enrichment is widely known to affect the root-associated arbuscular mycorrhizal fungal (AMF) community in different ways, for example, via altering soil properties and/or shifting host plant functional structure. However, empirical knowledge of their relative importance is still lacking. Using a long-term N addition experiment, we measured the AMF community taxonomic and phylogenetic diversity at the single plant species (roots of 15 plant species) and plant community (mixed roots) levels. We also measured four functional traits of 35 common plant species along the N addition gradient. We found divergent responses of AMF diversity to N addition for host plants with different innate heights (i.e. plant natural height under unfertilized treatment). Furthermore, our data showed that species-specific responses of AMF diversity to N addition were negatively related to the change in maximum plant height. When scaling up to the community level, N addition affected AMF diversity mainly through increasing the maximum plant height, rather than altering soil properties. Our results highlight the importance of plant height in driving AMF community dynamics under N enrichment at both species and community levels, thus providing important implications for understanding the response of AMF diversity to anthropogenic N deposition.

Increased cassava growth and yields through improved variety use and fertilizer application in the highlands of South Kivu, Democratic Republic of Congo

Nutrient limitations due to low soil fertility and insufficient fertilizer use widen cassava yield gaps in the Democratic Republic of Congo (DR Congo). This study was undertaken to investigate firstly the effects of variety and combined application of mineral fertilizer and organic (farm yard manure, FYM) inputs on cassava growth and yields, secondly to identify nutrient limitations to cassava production in the highland conditions of South Kivu, and thirdly to evaluate the economic benefits of the use of the improved variety and fertilizer in cassava production. Twenty-one multi-locational trials were conducted on farmers’ fields during two consecutive years. The use of an improved variety resulted in significant increases in both height and stem diameter in both years when fertilizer was applied; without fertilizer, both parameters were higher in the improved variety than in the local variety but only in the second year. Total biomass yield (storage root + stem) was significantly increased by 28% (11.2 t ha−1) through the use of an improved variety with fertilizer in the first year while in the second year, both total biomass and storage root yields were significantly increased by 58% (12.5 t ha−1) and 74% (9.8 t ha−1), respectively without fertilizer. Application of NPK+FYM resulted in significant increases in height and stem diameter over time, independent of the variety; and of total biomass, storage root and stem yields by 38% (11.5 t ha−1), 25% (5.1 t ha−1) and 63% (6.5 t ha−1), respectively relative to the unfertilized treatment. Sole application of mineral fertilizer and omission of macronutrients did not result in significant effects on storage root yields in both years. However, the application of NPK and NPK+ (Ca, Mg, S, Zn) significantly increased stem yield by 51% (6.0 t ha−1) and 56% (6.6 t ha−1), respectively while the omission of N significantly decreased both total biomass and stem yields by 31% (10.4 t ha−1) and 81% (8.0 t ha−1), respectively but only in the first year. Despite the lack of a significant response to applied N, P or K, addition of N and K increases storage root yield by 1.3 t ha−1 and 3.2 t ha−1 respectively (averages for both years). The findings reveal that the positive effects on cassava growth and yields and economic benefits from fertilizer are larger than the one from the choice of variety. Although the importance of combined application of mineral fertilizer and farm yard manure was demonstrated, no evidence of macronutrient limitations to cassava production was proven under the specific conditions of the study sites. A better understanding of the conditions under which positive effects of fertilizer occur can improve targeting and therefore achieve high profitability in cassava production.

Carbon nanomaterials are a superior soil amendment for sandy soils than biochar based on impacts on lettuce growth, physiology and soil biochemical quality

A significant bottleneck of current agricultural systems remains the very low agronomic efficiency of conventional agrochemicals, particularly in sandy soils. Carbon nanomaterials (CNMs) have been proposed to address this inefficiency in sandy soils, which could potentially improve soil fertility and enhance crop growth and physiological processes. However, the effects of different rates of CNMs on crop physiological and soil biochemical quality in sandy soils must be compared to other carbon sources (e.g., biochar) before CNMs can be broadly used. To address this, a 70-day pot experiment was set up, growing lettuce under ten treatments: a negative control with no CNMs, biochar or fertilizer; a fertilizer-only control; three CNMs-only unfertilized treatments (CNMs at 200, 400 and 800 mg kg−1 soil); two biochar treatments with fertilizer (biochar at 0.5% and 1% by soil mass + fertilizer); and three CNMs treatments with fertilizer (CNMs at 200, 400 and 800 mg kg−1 soil + fertilizer). A novel amorphous, water-dispersible, and carboxyl-functionalized CNMs with pH of 5.5, zeta potential of −40.6 mV and primary particle diameter of 30–60 nm was used for this experiment. Compared to the fertilizer-only control, CNMs applied at low to medium levels (200–400 mg kg−1) significantly increased lettuce shoot biomass (20–21%), total chlorophyll (23–27%), and fluorescence and photosynthetic activities (4–10%), which was associated with greater soil nutrient availability (N: 24–58%, K: 68–111%) and higher leaf tissue accumulation (N: 25–27%; K: 66%). Low to medium levels of CNMs also significantly increased soil biochemical properties, such as higher soil microbial biomass carbon (27–29%) and urease enzyme activity (34–44%) relative to fertilizer-only applications. In contrast, biochar (0.5%) increased lettuce biomass relative to fertilizer-only but had no significant effect on soil fertility and biological properties. These results suggest that CNMs at low to medium application rates are a superior carbon-based amendment relative to biochar in sandy soils.

Evaluation of eastern gamagrass as dual‐purpose complementary bioenergy and forage feedstock to switchgrass

AbstractSwitchgrass (SG) is considered a model bioenergy crop and a warm‐season perennial grass (WSPG) that traditionally served as forage feedstock in the United States. To avoid the sole dependence on SG for bioenergy production, evaluation of other crops to diversify the pool of feedstock is needed. We conducted a 3‐year field experiment evaluating eastern gamagrass (GG), another WSPG, as complementary feedstock to SG in one‐ and two‐cut systems, with or without intercropping with crimson clover or hairy vetch, and under different nitrogen (N) application rates. Our results showed that GG generally produced lower biomass (by 29.5%), theoretical ethanol potential (TEP, by 2.8%), and theoretical ethanol yield (TEY, by 32.9%) than corresponding SG under the same conditions. However, forage quality measures, namely acid detergent fiber (ADF), crude protein (CP), and elements P, K, Ca, and Mg were significantly higher in GG than those in SG. Nitrogen fertilizer significantly enhanced biomass (by 1.54 Mg ha−1), lignin content (by 2.10 g kg−1), and TEY (787.12 L ha−1) in the WSPGs compared to unfertilized treatments. Intercropping with crimson clover or hairy vetch did not significantly increase biomass of the WSPGs, or TEP and TEY in unfertilized plots. This study demonstrated that GG can serve as a complementary crop to SG and could be used as a dual‐purpose crop for bioenergy and forage feedstock in farmers' rotations.

Impacts of fertilization management strategies on improved sorghums varieties in smallholder farming systems in Mali: Productivity and profitability differences

Sorghum is an important cereal crop cultivated by smallholder farmers of Mali, contributing significantly to their food demand and security. The study evaluated different fertilization strategies that combined organic and inorganic fertilizer applications with three sorghum varieties. The experiments were conducted over three cropping seasons (2017–2019) in three sites (Bamako, Bougouni, and Koutiala respectively) within the Sudanian region of Mali. Our results showed a significant effect of season, variety, and fertilization strategies on grain and stalk yields. Grain yield increased by 8–40% in Koutiala, 11–53% in Bougouni, and 44–110% in Bamako while the average stalk yield was above 5000 kg ha−1 with fertilized treatment compared to unfertilized treatment in the three sites. Fadda performed the best variety, mean grain yield was 23% and 42% higher than that of Soumba and Tieble, respectively. Similarly, there was a progressive increase in grain yield with an increasing level of poultry manure (PM) from 0 to 150 g/hill and cattle manure (CM) from 0 to 100 g/hill. However, the application of 100 g/hill of CM and PM plus 3 g/hill of Di-ammonium Phosphate (DAP) increased yield by 8% and 12% respectively compared to only CM or PM treatments. The results further revealed higher yield gain by 51% (Bamako), 57% (Koutiala), and 42% (Bougouni) for T10-[PM (100 g/hill) + Micro-D_DAP (3 g/hill)] equivalent to 73 kgNha−1 than others (T2-T9), but not proportionate to the highest value-cost ratio (VCR). Radar charts used to visualize sustainable intensification (SI) performance in the three domains (productivity, profitability, and environment) showed that the environmental variable has a direct influence on productivity, meanwhile profitability across the strategies ranged from low to moderate value across sites and different fertilizer strategies. Our study, therefore, recommends the use of multiple-choice fertilizer strategies includingT2-CM (50 g/hill)+PM(50 g/hill), T5-DAP-Micro-D (3 g/hill), T6-DAP41:46:00 and T9-PM(50 g/hill) alongside with improved sorghum varieties tested, for higher productivity and profitability across the region.

Nitrogen‐15 evaluation of fertilizer placement at planting for corn production

AbstractNumerous studies have been reported to ascertain the benefits of starter fertilization for corn (Zea mays L.) production, but most rely on data collected by measuring early growth or grain yield at harvest. As a more conclusive evaluation, five field trials were conducted using 15N‐labeled urea‐ammonium nitrate (UAN) solution (90 kg N ha−1) to compare single and dual subsurface band placement, as well as surface dribble and broadcasting with incorporation. Significant differences in dry matter production and total N uptake occurred between fertilized and unfertilized treatments, but not among the different placements studied. In contrast, fertilizer 15N uptake efficiency (F15NUE) tended to be greater for either type of subsurface banding than for the dribble treatment, demonstrating the added sensitivity that can be achieved through isotopic measurements. More importantly, band placement consistently outperformed broadcasting, according to estimates of F15NUE for total aboveground biomass that ranged from 11% to 46% when UAN was banded and from 7% to 34% for broadcast applications.

Effects of fertilizer application on cacao pod development, pod nutrient content and yield

Fertilizer application in cacao production systems in West Africa yields highly variable results, ranging from no effect to doubling of the yield. Mechanisms underlying yield responses to increased nutrient availability are still largely unkown. In this study, we assessed how fertilizer application affects pod development and production of cacao trees in a full sun cocoa system in Côte d'Ivoire and a shaded cocoa system in Ghana. We monitored pod growth over time and the number of pods produced simultaneously on the trees in the minor and major harvest seasons. Furthermore, we measured nutrient concentrations in cherelles and beans and husks of developing pods in the major harvest season to estimate the total nutrients allocated to developing pods per tree. Lastly, we performed detailed yield measurements (number of pods, location in the tree (canopy or trunk), pod size and bean content) in 2020 for the plot in Côte d'Ivoire.Our results showed that, in the major harvest season, pods on fertilized trees grew wider (average: 15.4 cm) than pods on unfertilized trees (average: 11.9 cm). A higher pod growth rate resulted in a larger final pod size; larger pods took longer to mature. In the major harvest season, more cherelles on fertilized trees than on unfertilized trees reached maturity despite having an equal or lower nutrient content. Competition for assimilates rather than nutrients seems to induce cherelle wilt. In pods past wilting stage, fertilizer application slightly influenced nutrient dynamics of developing pods but not the final nutrient content in ripe pods. Lastly, increased nutrient availaibility did not change the absolute number of pods a tree produced annually. However, fertilizer application did increase the estimated annual dry bean yields from 2260 kg ha−1 to 2930 kg ha−1 by increasing the number of pods that developed during the major harvest season, when pods were heavier and the bean weight within the pods was relatively higher.

Use of soil nonexchangeable potassium by paddy rice with clay structural changes under long‐term fertilizer management

AbstractTo prove the hypothesis that paddy rice utilizes soil nonexchangeable potassium (neK) and causes associated structural changes in clay minerals, K status and clay mineralogy of 22 surface soils from three paddy fields under long‐term fertilizer management for 51–93 years were investigated. Soil neK content was determined as the difference between 1 mol L−1 hot HNO3 extractable K and 1 mol L−1 ammonium acetate exchangeable K. Clay mineralogy was identified by X‐ray diffraction (XRD). The radiocesium interception potential (RIP), an index of frayed edge sites in the interlayer sites of 2:1 type clay minerals, was also determined. The neK contents under the ‐K and NPK treatments were considerably lower than those under the unfertilized treatment in all the fields, indicating the exploitation of soil neK by rice. XRD analysis of the clay samples revealed 7% shift from the 1.0 peak to 1.4 nm one under the ‐K treatment compared with the unfertilized one, and the amounts of neK were negatively correlated with those of RIP (p < .01), suggesting the expansion of interlayer spaces of the 2:1 type phyllosilicates such as mica due to the release of neK. In addition, the neK content positively correlated with K balance of the long‐term experiments (p < .05). The differences of neK between unfertilized K and ‐K treatments corresponded to 22–157 kg K ha−1, or 0.42–1.68 kg K ha−1 year−1. In conclusion, utilization of considerable amount of soil neK under K depleted conditions should be considered to establish sustainable K management for paddy rice.

Effect of Biochar on Yield, Yield Components, and Macronutrients of Rice (Oryza sativa L.)

Biochar has recently caught researchers’ attention due to its potential of improving soil fertility and immobilizing pollutants and its emergence as a proper method of increasing crop yields. An experiment was conducted on the effect of chemical, ecological, and organic (biochar and compost) nutritional systems on yield and yield components of rice as a split-plot field experiment based on a randomized complete block design with three replications in two sites in Lahijan in 2018-2019. The experimental factors included nutrition at three levels (ecological, chemical, and control) as the main plot and the organic matter at four levels (urban waste compost, biochar, Azolla, and control) as the sub-plot. The combined application of chemical and organic fertilizers produced the highest grain yield, reflecting the positive effect of their combination on grain yield and yield components of rice cv. ‘Hashemi’. The results showed that the highest grain yield of 3699 kg ha-1 was related to the treatment of chemical fertilizer and biochar and the lowest (2209 kg ha-1 , i.e., a 40% decline) to the control (no chemical or biological fertilizer application). The highest number of fertile tillers and panicles per plant was obtained from the application of chemical fertilizer and biochar, the highest number of filled grains per panicle (116 grains) was observed in the application of chemical fertilizer and biochar at the university farm, and the lowest (84 grains) from the control (unfertilized treatment) at the Kateshal farm. The nutrient uptake was significantly higher in the chemical and biochar treatment than in the other treatments. Organic systems had varying impacts on rice yield and reduced the application of chemical fertilizers. Biochar contributed to increasing the growth, yield, and nutrient uptake of rice plants.

Strategies for high nitrogen production and fertilizer value of plant‐based fertilizers

AbstractBackgroundOrganic vegetable production has a demand for alternative fertilizers to replace fertilizers from sources that are not organic, that is, typically animal‐based ones from conventional farming.AimsThe aim of this study was to develop production strategies of plant‐based fertilizers to maximize cumulative nitrogen (N) production (equal to N yield by green manure crops), while maintaining a low carbon‐to‐nitrogen (C:N) ratio, and to test the fertilizer value in organic vegetable production.MethodsThe plant‐based fertilizers consisted of the perennial green manure crops—alfalfa, white clover, red clover, and a mixture of red clover and ryegrass—and the annual green‐manure crops—broad bean, lupine, and pea. The crops were cut several times at different developmental stages. The harvested crops were used fresh or pelleted as fertilizers for field‐grown white cabbage and leek. The fertilizer value was tested with respect to biomass, N offtake, N recovery, and soil mineral N (Nmin). Poultry manure and an unfertilized treatment were used as controls.ResultsThe cumulative N production of the perennial green manure crops ranged from 300 to 640 kg N ha–1 year–1 when cut two to five times. The highest productions occurred at early and intermediate developmental stages, when cut three to four times. Annual green manure crops produced 110–320 kg N ha–1 year–1, since repeated cutting was restricted. The C:N ratio of the green manure crops was 8.5–20.5, and increased with developmental stage. The fertilizer value of green manure, as measured in white cabbage and leek, was comparable to animal‐based manure on the condition that the C:N ratio was low (<18). N recovery was 20%–49% for green manure and 29%–42% for poultry manure. A positive correlation was detected between soil Nmin and vegetable N offtake shortly after incorporating the green manure crops, indicating synchrony between N release and crop demand.ConclusionsPlant‐based fertilizers represent highly productive and efficient fertilizers that can substitute conventional animal‐based fertilizers in organic vegetable production.

The effect of nitrogen fertilization on yield and macronutrient concentrations in root chicory (Cichorium intybus L. var. Sativus Bisch) and the health status of plants

The effect of N fertilization on the health status of chicory plants, yield and the content of dry matter and macronutrients in chicory roots was determined in the study. Three root chicory cultivars, Polanowicka, Orchies and Chrysolite, were grown in a plot experiment. Three levels of topsoil N fertilization were applied before sowing: 0, 80 and 120 kg ha–1. The severity of leaf diseases was estimated during the growing season. Root yield, agronomic and marginal N-use efficiency, DM content and macronutrient concentrations in roots were calculated after harvest (10–20 October). The symptoms of powdery mildew, gray mold and leaf spot on chicory leaves were significantly least severe in the unfertilized treatment. The highest yield (83 Mg ha–1) was obtained in 2017, in cv. Chrysolite without N fertilization. Root yield decreased in response to the application of N fertilizer at both rates. A minor increase in yield was observed only in cv. Polanowicka in N-fertilized treatments in 2017, and in cv. Chrysolite fertilized with 80 kg N ha–1 in 2018. Root yield was negatively correlated with disease severity during the growing season. The DM content of chicory roots (mean values for years of the study, cultivars and N rates) was similar in all treatments. N fertilization induced changes in the content of N, K, Mg and S in chicory roots of the analyzed cultivars. The application of N fertilizer had a beneficial influence on the N content of roots in all cultivars.

Indigenous Nutrient Supplying Capacity of Young Alluvial Calcareous Soils Favours the Sustainable Productivity of Hybrid Rice and Maize Crops

The crop productivity in calcareous soils is low due to their low organic matter content, high pH levels and improper nutrient management without considering the indigenous nutrient supplying capacity and crop yield potential; therefore, this study was conducted for a quantitative assessment of the nutrient supplying capacity of a calcareous soil on the productivity of hybrid and conventional rice and maize crops using an omission plot technique. The treatments included the ample application of Nitrogen (N), Phosphorus (P), Potassium (K), Sulphur (S) and Zinc (Zn), and an unfertilized check and omissions of N, P, K, S and Zn in rice and maize for six cropping seasons. The impact of the nutrient omission towards crop productivity was highest for nitrogen followed by phosphorous, potassium, zinc and sulphur. The total grain yield (3 yr average) in the hybrid rice–maize system was highest (16.32 t ha−1) for the optimum fertilized plot and lowest (6.34 t ha−1) for the unfertilized check. The sustainable yield index indicated that hybrid and conventional rice-maize cropping systems were more sustainable in the amply fertilized plot than in the nutrient-limited and unfertilized treatment plots. The average percent contributions of nitrogen, phosphorous, and potassium from the soil towards total nutrient removal were 36, 80 and 137 kg ha−1, in the hybrid system and 24, 54 and 104 kg ha−1 in the conventional system, respectively. The return on investment (ROI) of the N, P, K, S and Zn for the hybrid rice was 21.2, 7.1, 6.7, 4.1, and 0.3 USD, respectively, while for the maize it was 28.8, 7.6, 4.9, 6.5, and 0.7 USD, respectively. The results suggest that there is a direct link between the soil nutrient supplying capacity and the nutrient requirements by different types of crops in calcareous soil; therefore, the omission plot technique used for the assessment of the indigenous nutrient supplying capacity could be used in the larger domain for improved nutrient management, through synchronization with a targeted crop yield for improved productivity, soil fertility, nutrient use efficiency and farm income.

Rye-soybean double-crop: planting method and N fertilization effects in the North Central US

AbstractDouble-cropping winter rye cover crops (CC) with soybean in the North Central US could help with the global effort to sustainably intensify agriculture. Studies addressing the management of these systems are limited. Therefore, a field study was conducted from 2017 to 2019 in Central Iowa, US to evaluate winter rye CC biomass production, aboveground N accumulation, estimated economics, estimated within-field energy balance and estimated greenhouse gas (GHG) emissions under three N application rates (0, 60, 120 kg N ha−1) and three planting methods (pre- and post-harvest broadcast and post-harvest drilling). Averaged over N rates, all planting methods resulted in >5.0 Mg ha−1 year−1 rye aboveground biomass dry matter. Averaged over the 2-year study and compared with unfertilized treatments, applying 60 kg N ha−1 produced 1.1 Mg ha−1 more aboveground biomass (6.1 vs 5.0 Mg ha−1), accumulated 30 kg ha−1 more N in aboveground biomass (88 vs 58 kg N ha−1), and led to 20 GJ ha−1 more net energy. Biomass production was not significantly higher with 120 kg N ha−1 compared with the 60 kg N ha−1 rate. Even when accounting for an estimated 0.75 Mg ha−1 of above ground rye biomass left in the field after harvesting, more N was removed than applied at the 60 kg N ha−1 rate. The minimum rye prices over the 2-year study needed for double-cropping winter rye CC to be profitable (breakeven prices) averaged $117 and $104 Mg−1 for the 0 and 60 kg N ha−1 rates, which factors in estimated soybean yield reductions in 2019 compared with local averages but not off-site transportation. GHG emissions were estimated to increase approximately threefold between the unfertilized and 60 kg N ha−1 rates without considering bioenergy offsets. While environmental tradeoffs need further study, results suggest harvesting fertilized rye CC biomass before planting soybean is a promising practice for the North Central US to maximize total crop and net energy production.

Modelling pasture management practices for soil organic carbon gain in livestock systems

AbstractOur ability to develop strategies to mitigate climate change includes an understanding of, and our capacity to predict soil organic carbon (SOC) dynamics in livestock systems. Here we assess the capability of the Sustainable Grazing System (SGS) Pasture Model for predicting pasture growth (elongated wheatgrass, Thinopyrum ponticum) and SOC accumulation in different environments and under a range of pasture management practices in hydrohalomorphic soils located in South‐eastern Buenos Aires Province, Argentina. After Model calibration, aerial net primary productivity (ANPP) and TSOC content under two grazing intensities (7.5 and 11 cm post‐grazing target heights) and two N fertilization levels (0 and 100 kg N ha−1 yr−1) were simulated over a 10 year‐period. The SGS Pasture Model predicted 87% of the observed ANPP, with observed and predicted ANPPs averaging 1.46 and 1.42 Mg ha−1 yr−1, respectively. There were differences in simulated ANPP between fertilized and unfertilized treatments both at high and low grazing intensities for the last year of the period. Total SOC contents from the modelling showed differences between high (83.7 to 84.2 Mg ha−1) and low (86.8 to 87.5 Mg ha−1) grazing intensities, with treatments receiving N also showing higher carbon stocks. The positive effect of reduced grazing intensity on soil carbon was explained by an increased input of aerial and subterranean dry matter into the soil. Sensitivity analysis showed that SGS is a robust model, capable of performing effectively under a variety of conditions. Hence, it can be used for exploring management practices to mitigate the impact of livestock systems on emissions and SOC stocks.

Excessive nutrient input induces an ecological cost for aphids by modifying their attractiveness towards mutualist ants

Abstract Enhanced soil nutrient availability often favours herbivore performance by bringing the carbon:nutrient ratio of plants closer to herbivore requirements. However, a surplus of nutrients can promote a too low carbon:nutrient ratio in plants, making them of poor quality for herbivores. In addition, increased soil nutrients can trigger cascading effects altering higher trophic levels, resulting in indirect costs for herbivores. Through experiments under three increasing fertilization levels (unfertilized, NPK‐rich, and 2NPK‐rich soils), we studied how the enhancement of soil nutrient availability, by modifying the C:N ratio of thistles, affects the performance and homeostatic response of the aphids, and the consequent ant attraction. Fertilized soils increased the biomass and reduced the C:N ratio of thistles, also increasing aphid abundance. The stoichiometric homeostasis of aphids was modulated through changes in honeydew production and composition; fertilization treatments reduced by more than half the quantity of honeydew secreted and lead to 2.5–6.4 times higher honeydew N concentration compared with the unfertilized treatment. In addition, in the highest fertilization treatment, the aphids increased the content of uric acid (a waste toxic compound involved in amino acid deamination) excreted in their honeydew. Aphid‐infested thistles had the highest number of aphid‐tending ants when they grew on intermediate rich‐substrates. Ants selected honeydew with a lower C:N ratio (compared to unfertilized plants), but fewer workers patrolled plants with the highest fertilization treatment likely due to increased uric acid in the honeydew. We showed that enhanced soil nutrients brought plant C:N ratio closer to aphid requirements, enhancing their performance and promoting ant attendance. But a disproportionate increase in fertilization did not further improve aphid performance while it decreases the attraction of protective ants, which would make aphid populations more vulnerable to attack by natural enemies, inducing an ecological cost. This study highlights the complex role of bottom‐up cascading effects triggered by increases in soil nutrient availability and the importance of evaluating not only the physiological and population cost and benefits of it but also the ecological ones; especially when it alters mutualistic interactions. Read the free Plain Language Summary for this article on the Journal blog.

Fertilization reduces root architecture plasticity in Ulmus pumila used for afforesting Mongolian semi-arid steppe.

In this study, we assessed the functional and architectural traits in the coarse roots of Ulmus pumila trees, which are used for afforesting the semi-arid steppe of Mongolia. Tree growth was supported by different watering regimes (no watering, 2, 4, and 8 L h−1) and by two types of soil fertilization (NPK and compost). In July, 2019, for each of these treatments six trees, outplanted in 2011 as 2-year-old seedlings from a container nursery, were randomly selected, excavated by hand, and digitized. The build-up of root length correlated positively with increasing levels of watering for both soil depths analyzed. The application of fertilizers led to root growth suppression resulting in a general reduction of root length in a lowered rooting depth. When root system characteristics were analyzed in relation to wind direction, unfertilized trees showed higher root diameter values in both soil layers of leeward quadrants, likely a response to mechanical forces to improve stability. On the contrary, fertilized trees did not show differences in root diameter among the different quadrants underscoring a strong reduction in root plasticity with a lack of morpho-architectural response to the mechanical forces generated by the two prevailing winds. Finally, the root branching density, another important trait for fast dissipation of mechanical forces, was significantly reduced by the fertilization, independently of the quadrants and watering regime. Our results suggest that knowledge of the root response to the afforestation techniques applied in the semi-arid steppe of Mongolia is a necessary step for revealing the susceptibility of this forest shelterbelt to the exacerbating environmental conditions caused by climate change and, thus, to the development of a sustainable and successful strategy to restore degraded lands.

Responses of the root morphology and photosynthetic pigments of ryegrass to fertilizer application under combined petroleum-heavy metal stress.

With developments in industry, petroleum and heavy metal pollution are increasingly affecting soil, significantly harming the environment, biosecurity, and human health. Therefore, the remediation of contaminated soil is becoming increasingly important. In this study, ryegrass (Lolium perenne L.) was planted in petroleum-heavy metal co-contaminated soil with the application of nitrogen and phosphorus fertilizers. Three treatments were set up: uncontaminated soil + ryegrass (SH); petroleum-heavy metal co-contaminated soil + ryegrass (SPGH); and petroleum-heavy metal co-contaminated soil + ryegrass + nitrogen and phosphorus fertilizer (SPGH + NP). The results showed that the petroleum-heavy metal co-contamination promoted increases in the root length, surface area, volume, and diameter of ryegrass roots, increasing the below-ground biomass and decreasing the photosynthetic pigment content in the early stages of the experiment. The ratios of chlorophyll a/b and chlorophyll/carotenoid also increased. However, the application of fertilizer reduced the length, surface area, volume, and diameter of ryegrass roots in the co-contaminated soil, and the below-ground biomass decreased while the above-ground biomass increased. Furthermore, the photosynthetic pigment content was significantly higher than that in the unfertilized treatment and the chlorophyll a/b ratio decreased while the chlorophyll/carotenoid ratio increased. Therefore, fertilizers could alleviate the toxic effects of petroleum-heavy metal combined pollution on ryegrass roots and promote the synthesis of chlorophyll and other pigments, thus reducing the inhibitory effect of petroleum-heavy metal combined pollution on ryegrass growth and facilitating the remediation of the polluted soil.