Unfertilized Pastures Research Articles

Economic feasibility of extruded dried distillers grains cube as a supplement for beef steers grazing introduced mixed-grass pastures

Our objectives were to evaluate the effects of dried distillers grains (DDG) cubes (MasterHand Milling) on performance, and to assess the economics of steers grazing introduced pastures (n = 9 pastures; 7.2 ± 2.90 ha) in summer 2020 (n = 155 d) and 2021 (n = 182 d). Each year, crossbred steers (n = 140) were assigned to pastures, and pastures were assigned to 1 of 3 treatments (n = 3 pastures per treatment): (1) fertilized control (FC)—no supplement was given to steers on N-fertilized pastures (112 kg of N/ha); (2) fertilized supplement (FS)—steers were supplemented DDG cubes at 1.2 kg/d prorated for 3-d/wk feeding on N-fertilized pastures; or (3) supplement (SP)—steers were supplemented DDG cubes at 0.75% of BW/d prorated for 5-d/wk feeding on unfertilized pastures. Economic feasibility was determined each year using an enterprise budget analysis. Both FS and SP had greater ( P ≤ 0.01) mid-summer and final BW than FC steers. However, FS steers had greater total season supplemental efficiency ( P = 0.03) than SP. Cost of gain was the least ( P < 0.01) for FC animals and the greatest for SP ( P < 0.01). Supplementation increased gross returns ( P < 0.01), but FC had the greatest net returns ( P < 0.01). Our results suggest that DDG cubes are a suitable supplement and can replace N fertilizer for steers grazing introduced pastures, but the producer must determine the management strategy most profitable to meet their production goals.

PSIV-A-11 Effects of Supplementing Extruded Dried Distillers' Grains Cubes to Stocker Cattle Grazing Introduced Pastures on Subsequent Feedlot Performance and Carcass Characteristics

Abstract This research evaluated the effects of supplementing extruded dried distillers’ grains (DDG) cubes to grazing steers on subsequent finishing performance and carcass characteristics. Steers (n = 140) grazed tall fescue (Festuca arundinacea)/bermudagrass (Cynodon dactylon) pastures from 14 April to 17 September 2020 with supplementation treatments (n = 3 pastures/treatment) that included: 1) Fertilized Control (FC), no supplementation on N fertilized pastures (112 kg N/ha); 2) Fertilized Supplement (FS), supplemented DDG cubes at 2.9 kg/d prorated for 3-d/wk feeding on N fertilized pastures; and 3) Supplement (S), supplemented DDG cubes at 0.75% of BW/d prorated for 5-d/wk feeding on unfertilized pastures. All animals were followed through the finishing phase in a commercial feedyard to investigate carryover effects on feedlot performance in 2 pens comingled across supplemental treatment. Carcass characteristics were evaluated via ultrasonography on d0 and d84 of finishing, and measurements were obtained at harvest. Feed DMI were segregated to individual animals according to Guiroy et al. (2001) and Tedeschi and Fox (2020b). Supplemented animals were heavier (P &amp;lt; 0.01) at feedlot entry than FC, but harvest BW did not differ (P = 0.23). However, S and FS required 37 fewer days on feed (P = 0.01) than FC. Supplementation on pasture reduced total feed required (P = 0.02) and feed costs (P = 0.01) relative to FC. Gains were greater (P = 0.02) for FC and FS than S from d0 to d84, but did not differ thereafter (P ≥ 0.15). At harvest, FC had the greatest dressing percent (P &amp;lt; 0.01) and lower yielding carcasses than FS (P = 0.01), but did not differ (P = 0.11) from S. Overall, extruded DDG cube supplementation during grazing did not negatively affect subsequent feedlot performance or carcass characteristics, but reduced the total feed required for finishing.

Productivity of beef cattle grazing Brachiaria brizantha cv. Marandu with and without nitrogen fertilizer application or mixed pastures with the legume Desmodium ovalifolium

AbstractThe use of forage legumes to contribute biologically fixed nitrogen (N) to pastures is an alternative to increase beef cattle production in tropical regions. The objective was to compare the impact of the introduction of a legume with that of N fertilizer application on forage and animal production in Brachiaria pastures. This two‐year study assessed three pasture treatments: (1) mixed Marandu palisadegrass (Brachiaria brizantha [syn. Urochloa brizantha] cv. Marandu) and the legume “ovalifolium” (Desmodium ovalifolium) cv. Itabela (Mixed), (2) Marandu palisadegrass pastures with 150 kg N ha−1 (Fertilized), and (3) Marandu palisadegrass without N fertilizer (Unfertilized). Rotational stocking with a variable stocking rate was used with a target herbage allowance of 1.0 kg forage kg body weight−1. The pre‐grazing green herbage mass was similar for Fertilized and Mixed pastures, with 54% and 63% more mass than Unfertilized pasture, respectively (p &lt; .001). Cattle that grazed the fertilized pasture had the greatest average daily gain (ADG; p = .017). The stocking rate and liveweight gain per area were greatest for the Fertilized and Mixed pastures (p &lt; .001 and p &lt; .001, respectively). No differences between treatments were found for DM forage intake (p = .555). Organic matter digestibility was lowest (p &lt; .001) for the Mixed pasture. The inclusion of the ovalifolium legume in the Marandu pasture had the same impact on beef cattle production as annual fertilization with 150 kg N ha−1. The potential and environmental benefits of ovalifolium are discussed.

Effect of Foliage Dressing in Nano-Potassium Molybdate on Daily Gain and Antioxidant Function in Grazing the Chinese Merino Sheep.

The study was implemented for exploring influences of nano-K2MoO4 on the daily gain and antioxidant function of Chinese merino sheep in the native pasture, Xinjiang Uygur Autonomous Region, Northwest of China. Eighty of the sheep, weight of (45.56 ± 2.35) kg, were randomly distributed to the tested areas for 90 days, 20 sheep/group. The findings showed that the contents of Mo and N in the forage of applying nano-K2MoO4 were extremely higher than those in the control pastures (P <0.01). The daily gain in the fertilized groups were remarkably lower than that in the control group (P <0.01). The harvest of forage in the fertilized pastures were significantly higher than those in control (P <0.01). The contents of Mo in blood and liver in grazing the Chinese merino sheep were extremely higher than those from the control group (P <0.01). The contents of Cu in blood and liver in grazing the Chinese merino sheep were extremely lower than those in the unfertilized pastures (P <0.01). The levels of hemoglobin (Hb), blood platelet (PLT), and erythrocyte count (RBC) in animals from the fertilized pastures were extremely lower than those in the control pastures (P < 0.01). The activities of SOD, GSH-Px, and CAT in serum were significantly lower than those in group C. The serum MDA levels were significantly higher than those in the control group (P < 0.01). In conclusion, the application of nano-K2MoO4 in pastures can greatly improve the yield of forage, but strikingly decreased the daily gain and antioxidant function in grazing the Chinese merino sheep.

Profitability of Supplementing Dried Distillers’ Grains Cubes to Improve Animal Performance and Replace N Fertilizer for Steers Grazing Introduced Pastures

Abstract During the summer grazing season, steers grazing introduced forages are oftentimes provided supplemental protein and energy to improve animal performance. However, it is important to determine if the additional supplementation is economically beneficial. Therefore, the objective was to evaluate the profitability of supplementing dried distillers’ grains cubes (DDGS) to improve animal performance or replace the use of N fertilizer (112 kg N/ha from urea) for steers (n = 149; BW = 238 ± 13.8 kg) grazing mixed tall fescue (Festuca arundinacea)/bermudagrass (Cynodon dactylon) pastures (n = 9 pastures, 7.2 ± 2.90 ha) from April 14 to September 17 (n = 155 d) using an enterprise budget analysis. Main plot supplemental treatments (n = 3 pastures/treatment) included 1) Fertilized Control (FC), no supplementation on fertilized pastures; 2) Fertilized Supplement (FS), 2.9 kg/steer DDGS supplemented 3-d/wk on fertilized pastures; and 3) Supplement (S), supplemental DDGS at 0.75% BW/d prorated for 5-d/wk feeding on unfertilized pastures. The assumptions used in this analysis were based on actual costs of inputs for pasture management and the DDGS offered, as well as the 5-year average Oklahoma auction market prices for 227 kg steers in April and 386 kg steers in October. Total cost per hectare was greater for S (P &amp;lt; 0.01), was least (P &amp;lt; 0.01) for FC, and FS was intermediate (P &amp;lt; 0.01). Cost per kg gain for FS and S was greater (P &amp;lt; 0.01) than for FC. Gross return per hectare tended to be greatest for S (P = 0.06), but net return per hectare was less for FS and S (P &amp;lt; 0.01) than FC. Although FS and S allowed for improvement of animal performance, our results imply that FC was the most profitable due to the cost of supplementation and low supplemental efficiency of S and FS.

Effects of Dried Distillers’ Grains Cube Supplementation for Steers Grazing Introduced Pastures on Animal Performance and Forage Production

Abstract We evaluated the effects of supplementing dried distillers’ grains cubes (DDGS) and re-implantation of steers (n = 149; BW = 238 ± 13.8 kg) grazing tall fescue (Festuca arundinacea)/bermudagrass (Cynodon dactylon) pastures (n = 9 pastures, 7.2 ± 2.90 ha) from 14 April to 17 September 2020 (n = 155 d) in a split-plot design on steer performance and forage production. Main plot supplemental treatments (n = 3 pastures/treatment) included 1) Fertilized Control (FC), no supplementation on fertilized pastures (112 kg N/ha); 2) Fertilized Supplement (FS), supplemental DDGS fed at 2.9 kg 3-d/wk on fertilized pastures; and 3) Supplement (S), supplemented DDGS at 0.75% BW/d on unfertilized pastures prorated for 5-d/wk feeding. Steers were previously implanted during receiving with 40 mg trenbolone acetate and 8 mg estradiol (REV-G; Revalor G, Merck Animal Health). On July 7, steers in each pasture were randomly assigned to one of three re-implant treatments: 1) no re-implant; 2) REV-G; or 3) 200 mg progesterone and 20 mg estradiol (Synovex S, Zoetis Animal Health). Steers in FS and S gained more (P &amp;lt; 0.01) than FC throughout the trial and final BW was greater (P &amp;lt; 0.01) for FS and S compared with FC. Unexpectedly, re-implanting had no effect on ADG (P = 0.57) or BW (P = 0.34), but statistical power may be lacking. Supplemental efficiency was greater in the late summer for FS (P = 0.05) compared to S. Fertilizing pastures in FS and FC did not affect biomass (P = 0.39), however, CP was increased (P = 0.01) and acid and neutral detergent fibers tended to decrease (P = 0.06) relative to S in the early summer (April, May, June, and July), but did not differ in late summer (August and September). Based upon our analysis, DDGS is a suitable supplement and can replace N fertilizer for steers grazing introduced pastures.

Compost and legume management differently alter soil microbial abundance and soil carbon in semiarid pastures

AbstractEstablishment of improved perennial pasture systems for livestock production has been demonstrated to improve soil health in the semiarid Texas Southern High Plains (SHP). Use of waste products from other components of the animal production chain, such as applying composted manure from feedlot operations to grazed pastures, may provide an additional means of improving soil health and sustainability of these systems. However, few studies have examined the impact of composted animal manure on the changes in soil microbial communities, although they are important indicators of soil health. We investigated the effects of a one‐time composted cattle manure application at 3.36 Mg ha−1 on soil microbial community size and structure, soil organic C (SOC), total N (TN), and soil organic matter (SOM) up to 1.5 yr after application. We compared pastures consisting of either WW‐B. Dahl Old World bluestem grass [Bothriochloa bladhii (Retz.) S.T. Blake] alone or in mix with alfalfa (Medicago sativa L.). Results showed that compost application significantly increased SOC by about 4.4 g kg−1 soil within 1.5 yr after application. In N‐fertilized grass‐only pastures, compost addition increased microbial phospholipid fatty acid abundance, SOC, TN, and SOM, but no significant differences were observed between compost treatments in unfertilized pastures containing legumes. Our results show that even a one‐time compost addition at a relatively low rate can augment SOC in this semiarid pasture system after 1.5 yr, and that stimulation of soil microbial abundance and soil C and N from compost is more pronounced in fertilized grass‐only pastures compared with those with legume establishment.

Performance and economics of backgrounding yearling beef steers on smooth bromegrass pastures

This experiment was conducted to evaluate performance (using 5 yr of data reported here, and the additional 5 yr of results previously) and economic return (10 yr) of steers grazing smooth bromegrass pastures over 10 consecutive years to determine profitability and pasture longevity under 3 management strategies. Treatments consisted of cattle (n = 450; 45/yr) grazing smooth bromegrass pastures (n = 9/yr) fertilized with 90 kg of N/ha (FERT), unfertilized pastures stocked with cattle that received distillers grains plus solubles (DGS) daily at 0.6% of BW (SUPP), and unfertilized pastures stocked with cattle that received no supplement (control, CON). A randomized complete block design was used each year with 3 treatments present in each of 3 pasture blocks and treatments maintained in the same areas for all 10 yr. Cattle supplemented daily with DGS had greater ADG (1.19 kg/d; P < 0.01) than those on the CON and FERT treatments (0.83 and 0.86 kg/d, respectively; P = 0.44). Stocking rates for SUPP [10.95 animal unit months (AUM)/ha] and FERT (10.73 AUM/ha) cattle were similar to one another ( P = 0.75) and greater than those for CON (6.72 AUM/ha; P < 0.01). Net returns were greatest ( P < 0.01) for SUPP cattle ($146.56), with FERT ($130.04) and CON ($127.17) cattle being similar ( P = 0.62). In the current analysis, SUPP was the most profitable treatment in 7 of the 10 yr, with FERT being the most profitable 2 yr and CON 1 yr. Fluctuating market conditions and changes of input costs affect the overall profitability of treatments and relative differences. In this scenario, holding all prices constant except DGS, price of DGS would have to increase by 20% (increase of $43.29/908 kg) in order for applying N fertilizer to pastures (FERT) or increasing stocking rate (CON) to be more profitable than supplementing cattle with distillers grains (SUPP).

The effect of different grazing conditions on the insulin and incretin response to the oral glucose test in ponies

BackgroundThe oral glucose test (OGT) is a useful tool for diagnosing insulin dysregulation (ID) and is somewhat repeatable in ponies under consistent management. This study aimed to determine whether the insulin and incretin responses to an OGT in ponies differed after short-term access to fertilised pasture, compared to unfertilised pasture, by using a randomised, repeated measures study design.Sixteen mixed-breed ponies were classified as severely insulin-dysregulated (SD; post-prandial insulin ≥80 μIU/mL) or not severely insulin-dysregulated (NSD; post-prandial insulin < 80 μIU/mL) using an OGT prior to the study. The ponies accessed pasture that was fertilised, or unfertilised, for 5 days (4 h/day, with supplemental hay provided at 0.7% bodyweight), with a 10 day period between phases. An OGT was performed after each phase. Glucose, insulin, active glucagon-like peptide-1 (aGLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were measured in post-prandial blood samples.ResultsThe volume of fertilised pasture was five-fold greater than unfertilised pasture, with % non-structural carbohydrates (NSC) similar between all forages. Consuming fertilised pasture increased (P = 0.018) the serum insulin response to an OGT, compared to grazing unfertilised pasture. A limitation of the study was that pasture intake was unable to be quantified. Insulin responses were greater in SD, compared to NSD, ponies (P < 0.001) and remained well above the test cut-off at all times. A subset of ponies, initially screened as NSD, became (more) insulin-dysregulated after pasture access. Further, aGLP-1 was a significant predictor of insulin concentration in this cohort.ConclusionsWhereas some insulin-dysregulated ponies were comparatively resistant to dietary intervention, others showed markedly different OGT responses following subtle changes in their forage-based diet. This implies that mild/early ID might be unmasked by dietary change, and that dietary management is important in these ponies. However, dietary management alone may not be adequate for all cases of ID.

Measuring the Labile and Recalcitrant Pools of Carbon and Nitrogen in Forested and Agricultural Soils: A Study under Tropical Conditions

Soil organic carbon and nitrogen can be divided into labile and recalcitrant pools according to the time it takes to be cycled. The way in which carbon and nitrogen pools are cycled and distributed between labile and recalcitrant pools can directly relate to soil quality. This paper tested the hypothesis that labile and recalcitrant pools of carbon and nitrogen vary between agricultural soils with different species and fertilization management systems (nitrogen, phosphorus, and potassium need) under tropical conditions. This study aimed to examine the impact of land-uses on stocks and losses of carbon and nitrogen under tropical conditions. We explored labile (soil microbial biomass and labile carbon) and recalcitrant carbon pools (humin, humic acid, and fulvic acid) in forested and agricultural soils, defined as latosol (forest, fertilized pasture, and unfertilized pasture) and cambisol (forest, coast pasture, sugarcane, and silage corn). Forested soil was used as an appropriate use to soil conservation in tropical that presents levels adequate of carbon and nitrogen stocks and biological condition in soil. Results showed that pools of labile and recalcitrant carbon are different on soil layers and the use of soil. Forest use in cambisol and latosol promoted higher labile and recalcitrant pools of carbon and nitrogen due to the greater environmental stability without human intervention. On the other hand, human intervention occurred in fertilized pasture and coast pasture; however, both uses presented similar recalcitrant carbon and nitrogen pools when compared to forested soil on the soil surface due to fertilizer uses and the high volume of the grass root system. Overall, our findings reveal that under tropical conditions, agriculture and forested soil can present similar recalcitrant pools of carbon and nitrogen if agricultural soils are associated with the appropriate fertilizer management. Pasture with adequate fertilization management systems can be used as an alternative to recover degraded areas with low levels of recalcitrant carbon and nitrogen pools.

Organic carbon within soil aggregates under forestry systems and pasture in a southeast region of Brazil

The location of organic matter within the aggregate is a key factor for stabilizing and storing soil organic carbon (SOC). In this context, the purpose of this study was to answer the following question: How much is the contribution of aggregate associated-C in total SOC accumulation up to 1 m under different land uses in the Atlantic rainforest zone of Brazil? The experimental areas were: a secondary-forest; 3 and 5-year-old eucalyptus plantation; 35-year-old rubber tree plantation; and 50-year-old unfertilized pasture. Soil samples were collected at six different depths (0–10, 10–20, 20–40, 40–60, 60–80 and 80–100 cm), air dried and separated by wet-sieving into three fraction-size classes (2000–250 μm; 250–53 μm and <53 μm) – corresponding to macroaggregate, microaggregate and silt-and-clay size fraction, respectively. The ultrasonic method was used to quantify the C physically-protected in macro and microaggregates. Macroaggregates accumulated higher amounts of C (CMa) than microaggregates (CMi). The amount of CMa stock in all land-use systems ranged from 33 to 8 Mg ha−1, and the CMi ranged from 11 to 7 Mg ha−1. This represents around 22 to 4% and 7 to 4%, respectively, of physically protected C in the SOC storage up to 100 cm. The amount of CMa + CMi up to 1 m was 43 Mg ha−1 and 36 Mg ha−1 under 3- and 5-year-old eucalyptus plantations; 30 Mg ha−1 in the in secondary forest; and 19 Mg ha−1 in the rubber plantation and pasture. The C stabilization within aggregates represents a significant mechanism of C protection in these soils.

Dietary Nutritive Value, Dung Quality, Decomposition, and Nutrient Movement into Soil in Smooth Bromegrass Pastures

Legumes increase forage nutritive value in pastures; however, literature addressing the impacts on dietary nutritive value, dung quality, decomposition, and nutrient movement into soil remains scarce. Cattle grazing legume‐interseeded smooth bromegrass (Bromus inermis Leyss.) pastures may select diets with greater nutritive value and consequently produce dung that decomposes faster and increases nutrient movement into soil relative to cattle grazing N‐fertilized and unfertilized smooth bromegrass pastures. In 2014 and 2015, we collected rumen and dung samples from replicated experiments to evaluate effects of season (June and August), pasture type (legume‐interseeded, N‐fertilized, and unfertilized pastures), and harvest time (3, 7, and 30 d after deposition) on dietary nutritive value, dung quality, dung decomposition, and nutrient movement into soil. Cattle grazing legume‐interseeded pastures had similar dietary crude protein concentrations but 11% less dietary neutral detergent fiber concentrations than cattle grazing N‐fertilized pastures. Dung from cattle grazing legume‐interseeded pastures, meanwhile, had 5 to 12% greater N concentrations than dung from cattle grazing N‐fertilized and unfertilized pastures. From 3 to 30 d after deposition, dung C/N ratio decreased from 20.0 to 16.5; whereas, dry matter remaining diminished to 77.5%. Dung C/N ratio and dry matter remaining did not vary with season or pasture type. At Day 7, soil below dung from cattle grazing legume‐interseeded pastures had 20 and 42% greater inorganic N than soil below dung from N‐fertilized and unfertilized pastures. This research showed that pastures with legumes increases dietary nutritive value, resulting in greater dung quality and increased N movement into soil.

Organic phosphorus of soils under cacao agroforests in the Atlantic coast of Brazil

To increase the limited knowledge about phosphorus (P) species in strongly weathered soils of agroforests in tropical regions, the soil organic P was determined in different cacao (Theobroma cacao L.) agroforestry systems from the Atlantic forest region of Brazil, varying in age and phosphate fertilizer application. For this purpose NaOH-EDTA extraction and solution 31P nuclear magnetic resonance spectroscopy (31P NMR) were used. The studied areas were agroforests with different management systems: cacao-cabruca, cacao + erythrina, and cacao + rubber tree, which were compared with unfertilized pasture and natural forest. The results show that the distribution of P species in soil varied according to the different management practices (P fertilization, tree species and tree density) and stability time (different ages) of the cacao agroforests with low input of phosphate fertilizer. In cacao agroforests, natural forest and pasture a large portion of soil organic P (Po) consisted of P-monoester with lower concentrations of DNA. This Po species was correlated positively with clay and soil organic carbon. However, the recent conversion of natural forest and pasture to cacao agroforests led to a decrease in DNA concentration. High concentrations of pyrophosphate found in all cacao agroforests could be an evidence of a high soil fungal activity in cycling and accumulation of this P species. Moreover, the high concentrations and relative proportions of Po and pyrophosphate species revealed a high potential of P supply to trees in case of suppression of the phosphate fertilization in these agroforestry systems.

Production and quality of Tifton 85 pastures overseeded with black oat: effects of irrigation and nitrogen fertilization

The objective of this work was to evaluate the effects of irrigation and nitrogen fertilization on the bromatological quality, forage production, and botanical and structural composition of Tifton 85 (Cynodon sp.) pastures overseeded with black oat (Avena strigosa). Four treatments were evaluated in a 2 × 2 factorial scheme (irrigated and non-irrigated × fertilized and non-fertilized), with three replicates, in a completely randomized design. In irrigated paddocks, the irrigation system was activated when the soil matric potential reached a value equal to, or higher than, 10 kPa and 135 kg N ha-1 was applied to fertilized paddocks, divided into four applications. The forage mass pre- and post-grazing, total forage production, and the botanical, structural, and bromatological composition of the pastures were evaluated. No interaction was observed between the irrigation and nitrogen fertilization factors for any of the variables and no significant differences were observed in forage mass between pre- and post-grazing or in Tifton leaf and stem percentages. Nitrogen fertilization had a significant effect on forage production, which was 2626.41 kg dry matter (DM) ha-1 higher in fertilized pastures than in unfertilized pastures. In addition, fertilization resulted in a lower percentage of dead material (6.66%), higher percentage of oat leaves (30.84%), higher leaf:stem ratio (1:45), higher crude protein content (24.13%), lower levels of neutral detergent fiber (NDF) (64.57%) and acid detergent fiber (ADF) (32.86%), and higher in vitro dry matter digestibility (73.01%) than in unfertilized pastures. The use of irrigation did not influence total forage production, however, it resulted in pastures with lower NDF (65.97%) and ADF (33.54%), and higher in vitro dry matter digestibility (73.48%) than unirrigated pastures. Nitrogen fertilization produced improvements in pasture structure, associated with higher dry matter yield and bromatological quality, while irrigation only produced pastures with lower fiber content and greater digestibility.

The sequestration and turnover of soil organic carbon in subtropical leucaena-grass pastures

Abstract The sequestration of soil organic carbon (SOC) in agricultural systems has the potential to partially mitigate climate change by removing carbon dioxide (CO2) from the atmosphere. Furthermore, incorporating forage legumes into a grazing system may aid in C storage, as mature unfertilized pasture soils are typically nitrogen (N) limited. Leucaena leucocephala, a leguminous shrub, is often incorporated into grazing systems to provide a source of protein for cattle production. Additionally, leucaena improves the N fertility of grazing lands. Despite this, there is limited research on the C and N dynamics beneath leucaena-grass pastures, particularly at depth in the soil profile (1 m). We assessed the potential of leucaena to sequester SOC by estimating the origin (C3 or C4), quantity and vertical distribution of SOC stocks. A chronosequence of seasonally grazed leucaena stands (0, 9, 22, 34, 40 years) were sampled for organic C and natural δ13C abundance. Pasture type affected SOC stocks within the upper 0.2 m (grass C signature. Hence, SOC sequestration primarily occurred due to N accretion by leucaena (36 kg N ha−1 year−1) contributing to the increased C4 grass productivity, humus formation and slowed SOC decomposition. Therefore, there is a need to maintain soil fertility in grazed pastures to ensure SOC stocks are accreted and conserved.

The chemical nature of organic phosphorus that accumulates in fertilized soils of a temperate pasture as determined by solution 31P NMR spectroscopy

AbstractInefficiency of fertilizer phosphorus (P) use in grazing systems is often associated with the accumulation of inorganic and organic P in fertilized soil. However, the chemical nature of the accumulated organic P remains poorly understood. The aim of this study was to use solution 31P nuclear magnetic resonance (NMR) spectroscopy on sodium hydroxide–ethylenediaminetetraacetic acid (NaOH‐EDTA) extracts to identify the chemical nature of organic P in soils from a medium‐term (13 years) permanent pasture field experiment. This included an unfertilized pasture (P0), and treatments designed to maintain soil P fertility at near ‘optimum' (P1) and ‘supra‐optimum' (P2) levels for pasture growth; pastures at all levels of soil P fertility were continuously grazed with either a moderate or high stocking rate (SR09 and SR18). Approximately 20% of the fertilizer P added to pastures was recovered as organic P in NaOH‐EDTA extracts at the P1 level of soil P fertility in the 0–10 cm soil layer, and the majority (≈ 65%) of this was detected as the broad phosphomonoester signal. In addition, several specific forms of phosphomonoesters (myo‐ and scyllo‐inositol hexakisphosphate, α‐ and β‐glycerophosphate, and RNA mononucleotides) and phosphodiesters were detected across all soils but at low concentrations. This study shows that phosphate fertilization of pastures primarily results in the accumulation of complex forms of phosphomonoesters rather than that of specific forms of recognizable biomolecules (e.g., myo‐inositol hexakisphosphate).

Soil carbon stocks of Ultisols under different land use in the Atlantic rainforest zone of Brazil

Reforestation has a great potential on soil carbon sequestration resulting from continuous deposition of plant residues above- and belowground. The purpose of this study was to answer the following questions: (1) did reforestation with 35years old rubber tree plantation and 3 and 5years old eucalyptus plantations enhance SOC accumulation up to 1m depth? (2) How much did the conversion of forest into pasture changed the origin of SOC accumulated up to 1m depth? (3) How much did the conversion of pasture into eucalyptus plantation changed the origin of SOC accumulated up to 1m depth? The experimental area in this study was: 3-year-old eucalyptus plantation; 5-year-old eucalyptus plantation; 35-year-old rubber tree plantation and 50-year-old unfertilized pasture. SOC was determined by dry combustion in six layers (0–10, 10–20, 20–40, 40–60, 60–80 and 80–100cm). The natural abundance of 13C technique was used to determine the relative contributions of C3 and C4 plants derived C to the total SOC accumulated up to 100cm. Rubber tree showed significantly higher SOC stock (219Mgha−1) at a depth of 0–100cm. Pasture (176Mg C ha−1) and 3 (148Mg C ha−1) and 5years old (160Mg C ha−1) eucalyptus plantations had smaller C stocks and were similar to secondary forest (168Mg C ha−1) and there was a narrow variation of SOC storage over the soil profile. The differences in δ13C values were more pronounced in the upper soil layers and below 40cm these differences progressively decreased until a very small δ13C variation up to 100cm. Rubber tree plantation, compared to secondary forest, enhanced around 46Mgha−1 the SOC stored up to 1m depth and 2year old gap between the two eucalyptus plantations was enough to enhance the SOC accumulation in 14Mgha−1. The accumulation of SOC decreased slightly from 40 to 100cm. 50years after the conversion of forest into pasture allowed the incorporation around 33Mgha−1 of C4-derived C up to 100cm and around 14% of SOC accumulated in eucalyptus plantations was C4-derived C up to 100cm. The accumulation of SOC in all vegetable covers is still derived from the previous vegetation at a depth deeper than 60cm.

P transformations in cacao agroforests soils in the Atlantic forest region of Bahia, Brazil

Little is known about the phosphorus (P) fractions and P lability of agroforest soils in tropical regions, particularly those of cacao (Theobroma cacao L.) agroforests. We hypothesized that the effect of P fertilization on the distribution of P fractions in the soil based on the source-sink relationship differs for different cacao agroforestry systems. The cacao agroforestry systems studied were the following: open cacao-cabruca, closed cacao-cabruca, cacao + erythrina, mixed cacao + rubber tree, and cacao + rubber tree intercropping. A natural forest and an unfertilized pasture were used as reference systems. The P fractions were determined using the Hedley sequential extraction method, and the P transformation processes were evaluated via structural equation modeling. The impact of low P fertilizer input on the P fractions varied according to the specific environmental conditions of each cacao production system. Consequently, there was high dissimilarity among all of the cacao sites. In all of the cacao agroforestry systems, there was an increase in inorganic P (Pi), especially the labile fraction (resin-Pi and NaHCO3-Pi), but organic P (Po) increased only in the cacao + erythrina system and in the rubber tree planting row of the cacao + rubber tree intercropping system. As a result, the fitted structural models indicated that the inter-relationships of the geochemical processes were more important for determining the P availability than the biological processes. However, the Po concentrations and relative proportion were high in all of the cacao agroforestry systems, thereby revealing the high potential of supplying P to plants via the mineralization process in the eventual removal of mineral fertilization.

Lichen species richness is highest in non-intensively used grasslands promoting suitable microhabitats and low vascular plant competition

Lichens are very sensitive to habitat changes and their species richness is likely to decline under intensive land use. Currently, a comprehensive study analyzing lichen species richness in relation to land-use types, extending over different regions and including information on habitat variables, is missing for temperate grasslands. In three German regions we studied lichen species richness in 490 plots of 16 m2 representing different land-use types, livestock types, and habitat variables. Due to the absence of low-intensity pastures and substrates such as woody plants, deadwood and stones, there were no lichens in the 78 plots in Schorfheide-Chorin. In the two other regions, the richness of lichen species was 45 % higher in pastures than in meadows, and 77 % higher than in mown pastures, respectively. Among the pastures, the richness of all lichen species was on average 10 times higher in sheep-grazed pastures than in the ones grazed by cattle or horses. On average, the richness of all lichen species increased by 3.3 species per additional microhabitat. Furthermore, the richness of corticolous lichens increased by 1.2 species with 10 % higher cover of woody plants, lignicolous lichen species richness increased by 4.8 species with 1 % higher cover of deadwood, and saxicolous lichen species richness increased by 1.0 species with 1 % higher cover of stones. Our findings highlight the importance of low-intensity land use for lichen conservation. In particular, the degradation of grasslands rich in microhabitats and the destruction of lichen substrates by intensification, and conversion of unfertilized pastures formerly grazed at low intensity to meadows should be avoided to maintain lichen diversity.

Reduced Nitrogen Mineralization and Litter Decomposition in Unfertilized Smooth Bromegrass Pastures

ABSTRACTNitrogen fertilization has been shown to affect herbage accumulation, litter deposition, litter N return, and presence of weeds in smooth bromegrass (Bromus inermis Leyss.) pastures. The objective of this study was to evaluate the effect of pasture management strategies that varied amount and form of N input on soil N mineralization, litter decomposition, and litter N release in smooth bromegrass pasture. Management strategies included: (i) nitrogen‐fertilized pasture grazed with unsupplemented beef cattle (FERT); (ii) unfertilized pasture grazed with unsupplemented beef cattle (CONT); and (iii) unfertilized pasture grazed with dried distillers grains plus solubles (DDGS)‐supplemented beef cattle (SUPP). After 210 d of aerobic soil incubation, cumulative soil N mineralization was 155.1 ± 9.8, 170.5 ± 15.6, and 180.2 ± 13.8 mg N kg–1 soil for CONT, SUPP, and FERT pastures, respectively, which represented a supply of 254, 279, and 294 kg N ha–1 for the 0‐ to 15‐cm soil depth, respectively. Decomposition day models incorporating precipitation and temperature generally were the best predictors of litter decomposition. Regardless of the model used, there was no difference in litter decomposition among management strategies in 2010, while in 2011, both leaf and stem litter decomposed faster in FERT than CONT and SUPP pastures. After 8 yr of management, cessation of N fertilization in CONT and SUPP resulted in a soil environment that supported less litter decomposition than FERT.