Tropical Grasses Research Articles

Nutritive quality of two tropical grasses as influenced by cutting frequency

Nutritive quality of two tropical grasses as influenced by cutting frequency

The Detection of Nitrogen Saturation for Real-Time Fertilization Management within a Grassland Ecosystem

Unfettered agricultural activities have severely degraded vast areas of grasslands over the last decade. To rehabilitate and restore the productivity in affected grasslands, rangeland management practices still institute vast nitrogen-based fertilization regimes. However, excessive fertilization can often have damaging environmental effects. Over-fertilization can lead to nitrogen saturation. Although early indicators of nitrogen saturation have been documented, research detailing the near-real-time nitrogen saturation status of grasslands is required to better facilitate management protocols and optimize biomass production within degraded grasslands. Hence, the aim of this study was to discriminate nitrogen-saturated tropical grasses grown under a diverse fertilization treatment trial, using Worldview-3 satellite imagery and decision tree techniques. To accomplish this, nitrogen-saturated plots were first identified through specific physiological-based criteria. Thereafter, Worldview-3 satellite imagery (400–1040 nm) and decision tree techniques were applied to discriminate between nitrogen-saturated and -unsaturated grassland plots. The results showed net nitrate (NO3−-N) concentrations and net pH levels to be significantly different (α = 0.05) between saturated and non-saturated plots. Moreover, the random forest model (overall accuracy of 91%) demonstrated a greater ability to classify saturated plots as opposed to the classification and regression tree method (overall accuracy of 79%). The most important variables for classifying saturated plots were identified as: the Red-Edge (705–745 nm), Coastal (400–450 nm), Near-Infrared 3 (838–950 nm), Soil-Adjusted Vegetation Index (SAVI) and the Normalized Difference Vegetation Index 3 (NDVI3). These results provide a framework to assist rangeland managers in identifying grasslands within the initial stages of nitrogen saturation. This will enable fertilization treatments to be adjusted in near-real-time according to ecosystem demand and thereby maintain the health and longevity of Southern African grasslands.

Non-native Brachiaria humidicola with biological nitrification inhibition capacity stimulates in situ grassland N2O emissions.

Brachiaria humidicola, a tropical grass, could release root exudates with biological nitrification inhibition (BNI) capacity and reduce soil nitrous oxide (N2O) emissions from grasslands. However, evidence of the reduction effect in situ in tropical grasslands in China is lacking. To evaluate the potential effects of B. humidicola on soil N2O emissions, a 2-year (2015-2017) field experiment was established in a Latosol and included eight treatments, consisting of two pastures, non-native B. humidicola and a native grass, Eremochloa ophiuroide, with four nitrogen (N) application rates. The annual urea application rates were 0, 150, 300, and 450 kg N ha-1. The average 2-year E. ophiuroides biomass with and without N fertilization were 9.07-11.45 and 7.34 t ha-1, respectively, and corresponding values for B. humidicola increased to 31.97-39.07 and 29.54 t ha-1, respectively. The N-use efficiencies under E. ophiuroide and B. humidicola cultivation were 9.3-12.0 and 35.5-39.4%, respectively. Annual N2O emissions in the E. ophiuroides and B. humidicola fields were 1.37 and 2.83 kg N2O-N ha-1, respectively, under no N fertilization, and 1.54-3.46 and 4.30-7.19 kg N2O-N ha-1, respectively, under N fertilization. According to the results, B. humidicola cultivation increased soil N2O emissions, especially under N fertilization. This is because B. humidicola exhibited the more effective stimulation effect on N2O production via denitrification primarily due to increased soil organic carbon and exudates than the inhibition effect on N2O production via autotrophic nitrification. Annual yield-scaled N2O emissions in the B. humidicola treatment were 93.02-183.12 mg N2O-N kg-1 biomass, which were significantly lower than those in the E. ophiuroides treatment. Overall, our results suggest that cultivation of the non-native grass, B. humidicola with BNI capacity, increased soil N2O emissions, while decreasing yield-scaled N2O emissions, when compared with native grass cultivation.

Effect of the Interaction between Excreta Type and Nitrogen Fertilizer on Greenhouse Gas and Ammonia Emissions in Pastures

This study aimed to evaluate the emission factor of N2O, CH4, and the volatilization of NH3 for the combination of feces or urine with increasing doses of ammonium nitrate in tropical palisade grass pastures. The emission of greenhouse gases was assessed in eight treatments combining feces and urine with doses (75 and 150 kg of N ha−1) of ammonium nitrate, (32% N). The emission factor of N2O was 0.11, 0.19, and 0.17% for feces, urine, and 75 kg N ha−1 year−1 (as ammonium nitrate) and showed an additive linear effect when feces or urine were combined with increasing doses of N fertilizer. The emission factor of CH4 of feces (0.18 kg CH4 animal−1 year−1) was similar irrespective of combination with ammonium nitrate. The N loss by volatilized NH3 has a decreasing linear effect (p < 0.05) for the combination of feces or urine with ammonium nitrate. We concluded that N2O and CH4 emission factors of feces and urine in tropical climate conditions are lower than those reported by the IPCC. However, their N2O emission factors are sharply enhanced when combined with ammonium nitrate. These results may contribute to improvements in national and regional greenhouse gas inventories of livestock production.

Tropical grass silages with spineless cactus in diets of Holstein × Zebu heifers in the semiarid region of Brazil.

One of the factors that limit ruminant production in the semiarid region is the lack of roughage in the dry season. The management of forage plants adapted to edaphoclimatic conditions is a strategy to improve animal production. This study was conducted to examine the effects of biomass sorghum silage (BSS; Sorghum bicolor (L.) Moench) and BRS capiaçu grass silage (CGS; Pennisetum purpureum Schum) with or without spineless cactus (Opuntia spp.) in crossbred Holstein × Zebu heifers' diets on the intake, apparent digestibility of the nutrients and animal performance (e.g., final weight, daily weight gain) (experiment 1). Also, to evaluate the ruminal kinetics of dry matter (DM) and neutral detergent fiber (NDF) of roughages used in diets using two animals cannulated in the rumen (experiment 2). In experiment 1, ten heifers with an initial body weight of 200 ± 2.74kg (mean ± standard deviation) and a mean age of 10months were used. The animals were distributed in an experimental design in two simultaneous 5 × 5 Latin squares. Five experimental diets were used: diet 1, Volumax sorghum silage (VSS); diet 2, biomass sorghum silage (BSS); diet 3, BRS capiaçu silage (CGS); diet 4, biomass sorghum silage (60%) with spineless cactus (40%) (BSS + SC); and diet 5, BRS capiaçu grass silage (60%) with spineless cactus (40%) (CGS + SC). The diets were formulated with sorghum silage or BRS capiaçu grass silage with or without spineless cactus (roughage) and a maize- and soybean-based concentrate (75:25 roughage-to-concentrate ratio) on DM basis. The experiment lasted 105days, divided into five periods of 21days (17days for the adaptation of the animals to the diets and management and 4 for data collection and samples). The diets containing CGS and CGS + SC resulted in lower dry matter intake (DMI; 5.61kgday-1; P < 0.01), which was 19.4% lower than the diets with VSS, BSS, and BSS + SC (7.00kgday-1). The BSS + SC and CGS + SC diets showed higher crude protein digestibility (P < 0.01) at 21.9% than the other treatments (Volumax, BSS, CGS). The different diets did not change the final weight or the daily weight gain of the heifers. The BRS 716 biomass sorghum silage and BRS capiaçu grass combined with spineless cactus increased (P < 0.05) the intake of nonfibrous carbohydrates and did not interfere (P > 0.05) with the final weight or average daily gain of the crossbred Holstein × Zebu heifers. The standardized potentially degradable fraction (Bp) of the NDF was 13.91% higher (P < 0.01) for BSS and BSS + SC (61.6%) compared to the others (53.0%). A diet based on BSS + SC is recommended for feeding crossbred heifers in the growing phase.

Association of additives in supplemented grazing cattle during the finishing phase at the rainy season

The objectives were to evaluate the effects of monensin and virginiamycin, alone or combined, on supplemented Nellore cattle grazing tropical grass during the rainy season. Two experiments were conducted simultaneously to evaluate intake, digestibility, CH4 emissions, blood parameters, performance, and carcass characteristics (Exp. 1), and ruminal fermentation and relative abundance of ruminal microorganisms (Exp. 2). Animals (n = 92 Exp. 1 and n = 12 Exp. 2) were distributed in a completely randomized design and allocated in twelve paddocks [...]

Strategies of energy supplementation for cattle fed tropical forage and infrequently supplemented with protein

Our objective was to evaluate the effects of different energy supplementation strategies in Nellore heifers fed tropical grass forage and infrequently supplemented with nitrogen (N) compounds on voluntary intake, digestion, ruminal fermentation and fibre dynamics, urinary excretion characteristics, N balance, and hormonal and blood metabolic profile. Five rumen and abomasum fistulated Nellore heifers, averaging 332 kg of body weight, were used in a 5 × 5 Latin square design. The five treatments were: control, without supplementation; supplementation of 660 g of crude protein (CP) every 3 days; supplementation of 660 g of CP every 3 days and daily supplementation with 440 g of starch; supplementation of 660 g of CP and 1320 g of starch every 3 days; and supplementation of 660 g of CP and 1320 g of starch every 3 days, but starch supplementation was performed one day after CP supplementation. On average, treatments did not affect (P > 0.44) voluntary forage intake. However, the forage intake varied over the three-day supplementation cycle. Forage intake was depressed (P < 0.05) by protein supplementation alone on the first two days of the supplementation cycle, but increased on the third day. Only the concomitant supplementation with protein and starch caused a constant intake over the days. Ruminal fibre digestibility and the ruminal N balance were improved by supplementation (P < 0.05). A concomitant evaluation of serum urea N, rumen ammonia N, blood transaminases, and urinary excretion indicated that protein supplementation alone caused a hepatic N overload, which was improved when starch was concomitantly provided with protein. We concluded that infrequent protein supplementation causes negative impacts on hepatic metabolism and depresses voluntary forage intake, remarkably on the day the supplementation occurs. However, these negative effects on intake can be eliminated with adequate energy provision concomitantly with protein supplementation.

Evaluation of global Cenchrus germplasm for key nutritional and silage quality traits.

Cenchrus is important genera of grasses inhabiting tropical pastures and the Indian grasslands system. Its forage value is well established to sustain nomadic livestock and wildlife. This study deals with the evaluation of the representative set of global Cenchrus germplasm collection with 79 accessions belonging to six species (C. ciliaris, C. setigerus, C. echinatus, C. myosuroides, C. pennisetiformis, and C. biflorus) at flowering stage. Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose, and lignin values were in the range of 61.1-136, 640-749, 373-490, 277-375, and 35.6-75.50 g kg-1DM, respectively, while sugar contents varied from 11.6 to 101 mg g-1 DM. From the evaluated germplasm, 14 accessions of C. ciliaris having >70 mg g-1 DM sugar contents were selected and further evaluated for protein, fiber, carbohydrate and protein fractions, palatability indices, in vitro CH4 production, and ensiling traits. Protein contents were lower in EC397323 (61.8) and higher in IG96-96 (91.5), while the NDF, ADF, cellulose, and lignin contents varied between 678-783, 446-528, 331-405, and 39.6-62.0 g kg-1DM, respectively. The carbohydrate and protein fractions of selected accessions differed (p < 0.05), and the sugar contents varied (p < 0.05) between 74.6 and 89.6 mg-1g DM. Dry matter intake (DMI) and relative feed value (RFV) of accessions varied (p < 0.05) and were in the range of 1.53-1.77% and 58.2-73.8 g kg-1 DM, respectively. The total digestible nutrients (TDNs), digestible energy (DE), and metabolizable energy (ME) of selected accessions varied between 362-487 g kg-1 DM, 6.62-8.90, and 5.42-7.29 Mj kg-1 DM, respectively. In vitro gas and CH4 production (24 h) varied (p < 0.05) between 73.1 to 146 and 7.72 to 21.5 ml/g, respectively, while the degraded dry matter (g kg-1 DM) and CH4 (ml/g DDM) ranged between 399-579 and 17.4-47.2, respectively. The DM contents at ensiling, silage pH, and lactic acid contents of accessions differed (p < 0.05) and ranged between 185-345 g kg-1 DM, 5.10-6.05, and 1.39-23.3 g kg-1 DM, respectively. Wide genetic diversity existed in germplasm and selected C. ciliaris accessions for protein fiber, energy, sugar, and other nutritional traits. Silage prepared from EC397366, IG96-96, IG96-50, and EC397323 had pH and lactic acid contents acceptable for moderate to good quality silage of tropical range grasses.

Climate Change Allows Tropical Grasses to Cause Allergen Sensitization in the Temperate Region

Climate Change Allows Tropical Grasses to Cause Allergen Sensitization in the Temperate Region

A paleothermometer for the northern Andes based on C3–C4 grass phytoliths

AbstractGrass-dominated ecosystems cover ~40% of Earth's terrestrial surface, with tropical grasses accounting for ~20% of global net primary productivity. C3 (cool/temperate) and C4 (tropical and subtropical) grass distribution is driven primarily by temperature. In this work, we used phytolith assemblages collected from vegetation plots along an elevation and temperature gradient in the northern Andes (Colombia and Ecuador) to develop a paleothermometer for the region. To accomplish this, we created a transfer function based on the inverse relationship between mean annual temperature (MAT) and the phytolith-based climatic index (Ic), which is the proportion of C3 over C4 grass phytoliths (GSSCP). To evaluate how accurately the index reflects C4–C3 grass abundance in vegetation plots, we compared it with semiquantitative floristic estimates of C4–C3 grass abundance. To further evaluate the 1 − Ic index as a proxy for C4–C3 grass abundance, we compared it with corresponding δ13C values (an independent proxy for C4–C3 vegetation). Results indicate that (1) GSSCP assemblages correctly estimate C4–C3 grass abundance in vegetation plots; (2) the Ic index outperforms the δ13C record in estimating C4–C3 grass abundance, even in open-vegetation types; and (3) our Ic index–based model accurately predicts MAT. This new calibrated proxy will help improve paleotemperature reconstructions in the northern Andes since at least the emergence and spread of C4 grasses in the region during the late Miocene.

Effects of shading on tropical grass characteristics and cattle performance in silvopastoral systems: systematic review and meta-analysis

Context Shading reduces forage mass and can reduce animal production and profitability per area in silvopastoral systems (SPSs) with tropical grasses. This reduction in profitability is the main obstacle to using such systems. Aims This study evaluated the effects of shading by different tree arrangements on tropical grass characteristics and cattle performance in SPSs. Methods Systematic searches were conducted in databases and directly in scientific journals, and 66 articles were selected. Data were grouped into SPS subgroups on the basis of tree type: with Eucalyptus with 1–14 m between rows; with Eucalyptus with 15–28 m between rows; with Eucalyptus with more than 28 m between rows; with leguminous trees; with palm trees; and with other types of tree. Data were analysed with random-effects model by using mean difference with 95% confidence interval (at P = 0.05). Results A large reduction in forage mass significantly reduced animal weight gain per area and stocking rate of beef cattle reared in SPSs with row spacing of up to 28 m, compared with pasture monoculture. There was a small reduction in forage mass in SPSs with Eucalyptus with more than 28 m between rows, compared with pasture monoculture, but no reduction in stocking rate. This result allowed an increase in weight gain per area and indicated the need to use more than 28 m between Eucalyptus rows in systems the main objective of which is animal production. There was also a small reduction in forage mass in leguminous tree SPSs, but weight gain per area was similar to that in pasture monoculture; the animals also had a higher dry-matter intake, crude protein intake and milk production in these SPSs. The tropical grasses in palm tree SPSs had a higher crude protein and a lower forage mass than did those in pasture monoculture, and no reduction in weight gain per area compared with those in pasture monoculture, which indicated the possibility of productive animal production together with palm trees. The SPSs with other types of tree had a higher weight gain per area than did pasture monoculture. This result indicated that the use of SPSs with native trees can integrate animal production with environmental preservation. Conclusions The SPSs with Eucalyptus with more than 28 m between the rows or with other types of tree had a higher weight gain per area than did pasture monoculture, whereas leguminous and palm tree SPSs had a weight gain per area similar to that of pasture monoculture, which indicated that there was no significant negative effect of shading on livestock production. Implications Silvopastoral systems with higher weight gain per leaf area than, or similar to that of pasture monoculture can increase the total system production and profitability (considering wood and animal productions), which is beneficial and may be a factor in motivating producers to adopt these SPSs on commercial farms.

Defoliation management and nitrogen fertiliser rate affect canopy structural traits of grazed guineagrass (Megathyrsus maximus) cv. Zuri under rotational stocking

Context Defoliation management by grazing or clipping, combined with nitrogen (N) fertilisation, can increase forage production in tropical grasses. Use of pasture canopy height as a practical tool for monitoring forage mass and accumulation has been proposed because of the relationship between height and canopy light interception. However, this relationship can vary due to variations in canopy structural changes and N supply. Aims Our objectives were to study canopy structural responses and forage accumulation of grazed Zuri guineagrass (Megathyrsus maximus) under rotational stocking. Methods Combinations of two pre-graze canopy heights (55 and 75 cm) and two N fertilisation rates (150 and 300 kg N ha−1 year−1) were used during two consecutive years. Cattle grazed the pastures to 50% of pre-graze height. Key results Regardless of N rate, pastures managed at 75 cm always reached 95% light interception at pre-graze. The 55 cm/300 kg N pastures underwent structural changes such as greater leaf proportion, tiller population density and specific leaf area, and smaller mean foliage angle, which resulted in 95% light interception at pre-graze. Forage accumulation was 20% greater for 75 cm pastures (22 120 kg DM ha−1 year−1) than 55 cm pastures. Pastures receiving 300 kg N ha−1 year−1 had 38% greater forage accumulation than those receiving 150 kg N ha−1 year−1. Conclusion Zuri guineagrass pastures should be defoliated when canopy height reaches 75 cm owing to greater forage accumulation, but can be grazed at 55 cm when N is applied at 300 kg ha−1 year−1. Implications Zuri guineagrass can be managed with shorter pre-graze canopy height; when grazed at 55 cm and with 300 kg N ha−1 year−1, there is no negative effect on forage accumulation, allowing for shorter rest periods.

Nutrient composition, in vitro digestibility, and methane production of two tropical grasses: Effect of grazing frequency and plant spacing

Nutrient composition, in vitro digestibility, and methane production of two tropical grasses: Effect of grazing frequency and plant spacing

Fate of fertiliser nitrogen in a ryegrass–kikuyu dairy pasture system

Context Dairy pasture production is reliant on fertiliser to supply nitrogen (N); however, fertiliser N-use efficiency (FNUE) is low and N can be lost to the environment. Aims The aim of this study was to track the fate of N fertiliser applied in a pasture system of ryegrass (Lolium multiflorum, temperate grass) oversown into kikuyu (Pennisetum clandestinum, tropical grass). Methods We used 15N-labelled urea to track the residual plant uptake of a one-off application of 15N over three pasture cuts subsequent to the first cut in the kikuyu growing season from February 2018 to April 2018 (Experiment 1), followed by total soil and plant recoveries of 15N over a 12-month period (Experiment 2). Total N treatment rates were 0, 120, 240 and 480 kg N ha−1 year−1, consisting of application events of 40 kg N ha−1. In Experiment 1, 15N was applied only at the first fertilisation, whereas in Experiment 2, 15N-labelled urea was applied at each fertilisation event. Key results In Experiment 1, uptake of residual 15N fertiliser in the pasture biomass was &lt;6%. In Experiment 2, FNUE was 29–32% and unaccounted 15N fertiliser was 22–142 kg N ha−1, across the 120, 240 and 480 kg N ha−1 year−1 treatments. Conclusions Recovery of 15N residual fertiliser did not increase with N rate and was attributed to the mass increase in soil 15N recovery. FNUE in the pasture did not decrease with N rate. Unaccounted 15N increased with N rate. Implications Existing and alternative N and pasture management strategies such as clover and multi-species pasture need to be implemented and explored to reduce the amount of unaccounted N in dairy pasture production.

Genome-wide family prediction unveils molecular mechanisms underlying the regulation of agronomic traits in Urochloa ruziziensis.

Tropical forage grasses, particularly those belonging to the Urochloa genus, play a crucial role in cattle production and serve as the main food source for animals in tropical and subtropical regions. The majority of these species are apomictic and tetraploid, highlighting the significance of U. ruziziensis, a sexual diploid species that can be tetraploidized for use in interspecific crosses with apomictic species. As a means to support breeding programs, our study investigates the feasibility of genome-wide family prediction in U. ruziziensis families to predict agronomic traits. Fifty half-sibling families were assessed for green matter yield, dry matter yield, regrowth capacity, leaf dry matter, and stem dry matter across different clippings established in contrasting seasons with varying available water capacity. Genotyping was performed using a genotyping-by-sequencing approach based on DNA samples from family pools. In addition to conventional genomic prediction methods, machine learning and feature selection algorithms were employed to reduce the necessary number of markers for prediction and enhance predictive accuracy across phenotypes. To explore the regulation of agronomic traits, our study evaluated the significance of selected markers for prediction using a tree-based approach, potentially linking these regions to quantitative trait loci (QTLs). In a multiomic approach, genes from the species transcriptome were mapped and correlated to those markers. A gene coexpression network was modeled with gene expression estimates from a diverse set of U. ruziziensis genotypes, enabling a comprehensive investigation of molecular mechanisms associated with these regions. The heritabilities of the evaluated traits ranged from 0.44 to 0.92. A total of 28,106 filtered SNPs were used to predict phenotypic measurements, achieving a mean predictive ability of 0.762. By employing feature selection techniques, we could reduce the dimensionality of SNP datasets, revealing potential genotype-phenotype associations. The functional annotation of genes near these markers revealed associations with auxin transport and biosynthesis of lignin, flavonol, and folic acid. Further exploration with the gene coexpression network uncovered associations with DNA metabolism, stress response, and circadian rhythm. These genes and regions represent important targets for expanding our understanding of the metabolic regulation of agronomic traits and offer valuable insights applicable to species breeding. Our work represents an innovative contribution to molecular breeding techniques for tropical forages, presenting a viable marker-assisted breeding approach and identifying target regions for future molecular studies on these agronomic traits.

DIGESTIBILITY OF ADDITIONAL CRUDE PROTEIN FROM TROPICAL LEGUMES IN MIXED GRASS-LEGUME RATIONS FOR RUMINANTS

The digestibility of crude protein (CP) from tropical legumes in grass-legume mixed diets was studied based on literature data by regressing the digestible CP (digCP) on the proportion of CP from legumes in the diet. In vivo studies reporting on CP concentration and in vivo CP digestibility values of ruminants fed diets with tropical legumes and grasses with no other feed, were selected for the analysis (56 publications, 213 dietary treatments (150 legume forages, 63 grasses)). First, observations were classified into categories based on the CP concentration of the control grass using the first and the third quartile of the grass CP concentration (LOW, MEDIUM, and HIGH grass quality). Second, legumes were divided based on their growth habit: herbs, shrubs, and trees. Based on the slopes and coefficients of the regressions of the digCP supply on the proportion of CP from legumes, CP digestibility of legumes was higher than that of LOW quality grasses, but lower than that of MEDIUM and HIGH quality grasses. Furthermore, the digestibility of the additional CP from legumes was higher when combined with MEDIUM quality grasses (0.493) compared with those of LOW quality (0.432), while it decreased when combined with HIGH quality grasses (0.305). No differences appeared in the digestibility of additional CP from legumes depending on their growth habit (range 0.415 to 0.421). These results can help optimize the assimilation of CP supplemented by tropical legumes.

Voluntary intake and digestibility of lambs fed hay of forage soybeans cv. ‘Rongai’ [Lablab purpureus (L.) Sweet

Sun cured hays of two legumes, forage soybean (Glycine max L. Merr.) cv. ‘Hinson Long Juvenile’ and Lablab [Lablab purpureus (L.) Sweet] cv. ‘Rongai’, were compared in terms of voluntary intake and digestibility of dry matter (DM), crude protein, and neutral detergent fiber, in six individually caged lambs (28.4 ± 4 kg body weight). Treatments were arranged in a completely randomized design with three replicates (animals). The lambs were fed periodically during a seven-day adaptation period, and data collection was carried out over five days. ‘Hinson’ and ‘Rongai’ did not differ in crude protein (15.8 vs. 15.5%) and neutral detergent fiber (56.2 vs. 55.1% of DM). Lambs fed cv. ‘Hinson’ consumed more DM (P&lt;0.05) than those fed ‘Rongai’ (945 vs. 853 g/d). ‘Hinson’ also registered higher DM digestibility (56.2 vs. 49.6%) than ‘Rongai’. Based on their agronomic characteristics, chemical composition, voluntary intake, and digestibility, both legumes exhibit good potential for use as hay. Large-scale planting of these legumes could supply hay for ruminant feeding to supplement low quality tropical grasses and reduce the need for imported protein sources for ruminant feeding.

Resposta de genótipos de Urochloa mosambicensis à adubação fosfatada em solo com baixo nível de fósforo

Abstract Phosphorus (P) is one of the main nutrients capable of increasing yields of tropical grasses. The definition of adequate P fertilizer rates can contribute to improving forage production of pastures. However, the efficiency in the response of different genotypes of Urochloa mosambicensis (Hack.) Dandy (Bushveld herringbone grass) to P fertilizer rates is not known. This study aimed to quantify the response of U. mosambicensis genotypes to P fertilizer levels and classify the genotypes as to efficiency and responsiveness. The experiment was carried out in pots, under controlled conditions, in a completely randomized design, in a 2 x 9 factorial with five replications. The factors consisted of equivalent P rates of 10 and 90 kg ha-1 of P2O5 (triple superphosphate) and eight genotypes of U. mosambicensis (UmCO-1 (2), UmCO-2 (2), UmCO-4 (1), UmCO-8 (1), UmCO-11 (2), UmCO-12 (2), UmCO-13 (2) and UmCO-14 (2)), in addition to a control, Urochloa brizantha syn. Brachiaria brizantha cv. BRS Piatã. Each experimental unit consisted of one pot. Biometric attributes and dry mass yield were evaluated over four cutting cycles. There was no effect of the P fertilization x genotypes interaction for the variables evaluated. However, the highest fertilizer rate increased dry mass yield and tiller population density in all genotypes and cuttings evaluated. The genotype UmCO-4 (1) and the cultivar BRS Piatã proved to be responsive to and efficient in P use. The highest P rate promoted greatest production of dry mass and greatest number of tillers in all genotypes of U. mosambicensis.

Differential responses of yield and shoot traits of five tropical grasses to nitrogen and distance to trees in silvopastoral systems

Context Light intensity and nitrogen availability are important factors influencing the growth of C4 forage species. Trade-offs may occur in the adaptive responses of species to shading and nitrogen inputs, and functional shoot traits can help to explain the consequences of these responses for species performance. Aims Our objective was to gain understanding of the mechanisms involving shoot traits of grasses that determine above-ground dry matter yield (DMY) when resources, light and nitrogen all vary. Methods Five C4 perennial forage grasses were grown in six shading conditions (full sunlight vs five positions between Eucalyptus dunnii rows) with two nitrogen levels (0 vs 300 kg N ha−1 year−1) and clipped when the canopy reached 95% light interception. Path analysis was used to explore the relationship between DMY, shading levels, nitrogen nutrition index and shoot traits. Key results Yield increased between 126 and 569 g dry matter m−2 with nitrogen fertilisation. Plant nitrogen concentration was the most important predictor of DMY. Increased shading reduced DMY by 6.94–12.5 g dry matter m−2 for each 1% increase in shading. DMY was also modulated by shoot traits such as specific leaf area, sheath length and leaf area index (via leaf area and tiller density), but with different responses according to species. Conclusions The five species compared adopted different mechanisms involving shoot traits, revealing different strategies to cope with changes in light and nitrogen availability. Implications Agroforestry practitioners may want to choose forages that are more likely to maintain biomass yield as trees grow.

Economic Analysis for Yield and Carrying Capacity of Intercropped Indigofera (Indigofera zollingeriana) and Brahum (Brachiaria humidicola)

Through efficient asset management, blended societies can boost plant growth and yield. The explanation of this consider was to choose the reach similar extent of the got crops leguminosae Indigofera zollingeriana (Iz) and the tropical grass Brachiaria humicola (Bh). The explanation of this contemplate was to study the show up tantamount extent of this got alter in view of abandon and bearing limit. This test was carried out with a plan that was completely random, and it used a combination of four drugs from the planted area as follows: We used the ANOVA and HSD test to analyze the data for combination planted (C): C1, Iz planted range, which had 1.0 mx 1.0 m and Bh planted zone, which had 0.5 m x 0.25 m; C2, Iz planted range, which had 1.0 mx 1.0 m and Bh planted zone, which had 0.5 m x 0.5 m: C3, Iz planted range, which had 1.0 mx 1.5 m and Bh planted zone, which had 0.5 m x 0.25 m; C4, Iz planted range, which had 1.0 mx 1.5 m and Bh planted zone, which had 0.5 m x 0.5 m. The elements estimated were the expected acquiescence and conveying limit in view of dry matter and carrying capacity acquiescence for logical financial. The results appeared to be essentially different (P&lt;0.01). The improved grain yields of intercrop in C3 have highest the total grain yield, carrying capacity and the net-income. Overall, these findings imply that following the optimum grain yields, and competitive interactions of intercrop species can be improved. It very well may be reasoned that Iz covered crops with an established area of 1.0 m x 1.5 m and Bh with an establishing area of 0.5 m x 0.25 m have the most fitting financial of yield and conveying limit.