Root Growth,Nutrient Uptake,and Nutrient-Use Efficiency by Roots of Tropical Legume Cover Crops as Influenced by Phosphorus Fertilization

Roots are important organs that supply water and nutrients to growing plants. Data related to root growth and nutrient uptake by tropical legume cover crops are limited. The objective of this study was to evaluate root growth of tropical legume cover crops and nutrient uptake and use efficiency under different phosphorus (P) levels. The P levels used were 0 (low), 100 (medium), and 200 (high) mg kg^?1 of soil, and five cover crops were evaluated. Root dry weight, maximum root length, and specific root length were significantly influenced by P and cover crop treatments. Maximum values of these root growth parameters were achieved with the addition of 100 mg P kg^?1 soil. The P?×?cover crops interactions for all the macro- and micronutrients, except manganese (Mn), were significant, indicating variation in uptake pattern of these nutrients by cover crops with the variation in P rates. Overall, uptake pattern of macronutrients was in the order of nitrogen (N) > calcium (Ca) > potassium (K) > magnesium (Mg) > P and micronutrient uptake pattern was in the order of iron (Fe) > Mn > zinc (Zn) > copper (Cu). Cover crops which produced maximum root dry weight also accumulated greater amount of nutrients, including N, compared to cover crops, which produced lower root dry weight. Greater uptake of N compared to other nutrients by cover crops indicated that use of cover crops in the cropping systems could reduce loss of nitrate (NO₃ ^?) from soil–plant systems. Increase in root length and root dry weight with the addition of P can improve nutrient uptake from the soil and lessen loss of macro- and micronutrients from the soil–plant systems.     

Soil Phosphorous Influence on Growth and Nutrition of Tropical Legume Cover Crops in Acidic Soil

In tropical regions, use of cover crops in crop production is an important strategy in maintaining sustainability of cropping systems. Phosphorus (P) deficiency in tropical soils is one of the most yield-limiting factors for successful production of cover crops. A greenhouse experiment was conducted to evaluate influence of P on growth and nutrient uptake in 14 tropical cover crops. The soil used in the experiment was an Oxisol, and P levels used were low (0 mg P kg^?1), medium (100 mg P kg^?1) and high (200 mg P kg^?1). There was a significant influence of P and cover crop treatments on plant growth parameters. Phosphorus X cover crops interaction for shoot dry weight, root dry weight and root length was significant, indicating different responses of cover crops to variable P levels. Based on shoot dry weight efficiency index (SDEI), legume species were classified into efficient, moderately efficient or inefficient groups. Overall, white jack bean, gray mucuna bean, mucuna bean ana and black mucuna bean were most P efficient. Remaining species were inefficient in P utilization. Macro- and micronutrient concentrations (content per unit dry weight of tops) as well as uptakes (concentration x dry weight of tops) were significantly (P < 0.01) influenced by P as well as crop species treatments, except magnesium (Mg) and zinc (Zn) concentrations. The P x crop species interactions were significant for concentration and uptake of all the macro and micronutrients analyzed in the plant tissues, indicating concentrations and uptake of some nutrients increased while others decreased with increasing P levels. Hence, there was an antagonistic as well as synergetic effect of P on uptake of nutrients. However, uptake of all the macro and micronutrients increased with increasing P levels, indicating increase in dry weight of crop species with increasing P levels. Overall, nutrient concentration and uptake in the top of crop species were in the order of nitrogen (N) > potassium (K) > calcium (Ca) > Mg > sulfur (S) > P for macronutrients and iron (Fe) > manganese (Mn) > zinc (Zn) > copper (Cu) for micronutrients. Interspecific differences in shoot and root growth and nutrient uptake were observed at varying soil P levels     

Growth of Tropical Legume Cover Crops as Influenced by Nitrogen Fertilization and Rhizobia

Tropical legume cover crops are important components in cropping systems because of their role in improving soil quality. Information is limited on the influence of nitrogen (N) fertilization on growth of tropical legume cover crops grown on Oxisols. A greenhouse experiment was conducted to evaluate the influence of N fertilization with or without rhizobial inoculation on growth and shoot efficiency index of 10 important tropical cover crops. Nitrogen treatment were (i) 0 mg N kg^?1 (control or N₀), (ii) 0 mg N kg^?1 + inoculation with Bradyrhizobial strains (N₁), (iii) 100 mg N kg^?1 + inoculation with Bradyrhizobial strains (N₂), and (iv) 200 mg N kg^?1 of soil (N₃). The N?×?cover crops interactions were significant for shoot dry weight, root dry weight, maximal root length, and specific root length, indicating that cover crop performance varied with varying N rates and inoculation treatments. Shoot dry weight is considered an important growth trait in cover crops and, overall, maximal shoot dry weight was produced at 100 mg N kg^?1 + inoculation treatment. Based on shoot dry-weight efficiency index, cover crops were classified as efficient, moderately efficient, and inefficient in N-use efficiency. Overall, the efficient cover crops were lablab, gray velvet bean, jack bean, and black velvet bean and inefficient cover crops were pueraria, calopo, crotalaria, smooth crotalaria, and showy crotalaria. Pigeonpea was classified as moderately efficient in producing shoot dry weight.     

NUTRIENT UPTAKE AND USE EFFICIENCY BY TROPICAL LEGUME COVER CROPS AT VARYING PH OF AN OXISOL

Oxisols comprise large soil group in tropical America. These soils are acidic and have low fertility. Use of tropical legume cover crops in cropping systems is an important strategy to improve fertility of these soils for sustainable crop production. Data are limited on nutrient uptake and use efficiency of tropical cover crops under different acidity levels. The objective of our study was to evaluate growth and nutrient uptake parameters of sixteen tropical legume cover crops under three soil pH (5.1, 6.5, and 7.0) of an Oxisol. Shoot dry weight was influenced significantly by pH and cover crop treatments and their interactions, indicating that cover crops used had differential responses to changing soil pH levels. Overall, shoot dry weight decreased when soil pH was raised from 5.1 to 7.0, indicating acidity tolerance of cover crops. Nutrient concentration (content per unit of dry weight), uptake (concentration X dry weight), and nutrient use efficiency (dry weight of shoot per unit of nutrient uptake) varied significantly among cover crops. The variation in nutrient uptake and use efficiency among cover crop species was associated with variation in shoot dry matter production. Significant variation among crop species in dry matter production and low C/N ratios (average value of 14.25) suggest that cover crops which produced higher dry matter yield like white jack bean, gray mucuna bean, black mucuna bean, mucuna bean ana, and lablab are important choices for planting in tropical soils to recover large amount of macro and micronutrients, and to prevent such nutrient leaching in soil plant systems.     

Differential Soil Acidity Tolerance of Tropical Legume Cover Crops

In tropical regions, soil acidity and low soil fertility are the most important yield‐limiting factors for sustainable crop production. Using legume cover crops as mulch is an important strategy not only to protect the soil loss from erosion but also to ameliorate soil fertility. Information is limited regarding tolerances of tropical legume cover crops to acid soils. A greenhouse experiment was conducted to determine the differential tolerance of 14 tropical legume cover crops to soil acidity. The acidity treatments were high (0 g lime kg^?1 soil), medium (3.3 g lime kg^?1 soil), and low (8.3 g lime kg^?1 soil). Shoot dry weight of cover crops were significantly affected by acidity treatments. Maximum shoot dry weight was produced at high acidity. Jack bean, black mucuna, and gray mucuna bean species were most tolerant to soil acidity, whereas Brazilian lucern and tropical kudzu were most susceptible to soil acidity. Overall, optimal soil acidity indices were pH 5.5, hydrogen (H)+ aluminum (Al) 6.8 cmol_c kg^?1, base saturation 25%, and acidity saturation 74.7%. Species with higher seed weight had higher tolerance to soil acidity than those with lower seed weight. Hence, seed weight was associated with acidity tolerance in tropical legume species.     

Growth,Nutrient Uptake,and Use Efficiency in Dry Bean in Tropical Upland Soil

Dry bean (Phaseolus vulgaris L., cv. ‘BRS Requinte’) is an important legume crop and nutrient availability is one of the most yields limiting factors for bean production in tropical upland soils. A greenhouse experiment was conducted in Brazilian Oxisol to study growth, nutrient uptake, and use efficiency of macro- and micronutrients during growth cycle of bean plant. Plants were harvested at 15, 30, 45, 60, 73, and 99 days after sowing for determination of growth parameters and uptake of nutrients. Root dry weight, shoot dry weight and leaf trifoliate increased significantly (P< 0.01) in a quadratic fashion with the advancement of plant age. However, root-shoot ratio decreased significantly with increasing plant age. Concentrations of nitrogen (N), calcium (Ca), magnesium (Mg), and zinc (Zn) decreased with the advancement of plant age. However, concentrations of phosphorus (P), potassium (K), copper (Cu), and manganese (Mn) increased significantly with the advancement of plant age. Accumulation of macro- and micronutrients significantly increased with the increasing plant age. Accumulation of N, P, K and Cu was higher in the grain compared with root and shoot, indicating relatively higher importance of these nutrients in improving grain yield of dry bean. Nitrogen, P and Cu use efficiency was higher for shoot weight compared to grain weight. For grain production, nutrient use efficiency was in the order of Mg > Ca > P > K > N for macronutrients and Cu > Zn = Mn for micronutrients.     

Macronutrient-Use Efficiency and Changes in Chemical Properties of an Oxisol as Influenced by Phosphorus Fertilization and Tropical Cover Crops

Cover crops are important components of copping systems due to their beneficial effects on soil physical, chemical, and biological properties. A greenhouse experiment was conducted to evaluate influence of phosphorus (P) fertilization on nutrient-use efficiency of 14 tropical cover crops. The P levels tested were 0 (low), 100 (medium), and 200 (high) mg kg^?1 of soil. The cover crops tested were Crotalaria breviflora, Crotalaria breviflora, Crotalaria spectabilis Roth, Crotalaria ochroleuca G. Don, Crotalaria juncea L., Crotalaria mucronata, Calapogonium mucunoides, Pueraria phaseoloides Roxb., Pueraria phaseoloides Roxb., Cajanus cajan L. Millspaugh, Dolichos lablab L., Mucuna deeringiana (Bort) Merr., Mucuna cinereum L., and Canavalia ensiformis L. DC. Agronomic efficiency (shoot dry weight per unit P applied), physiological efficiency (shoot dry weight per unit of nutrient uptake), and apparent recovery efficiency (nutrient uptake in the shoot per unit nutrient applied) were significantly varied among cover crops. Agronomic efficiency decreased with increasing P levels. Overall, physiological efficiency of nutrient uptake was in the order of P > sulfur (S) > magnesium (Mg) > calcium (Ca) > potassium (K) > nitrogen (N). Similarly, apparent recovery efficiency was in the order of N > K > Ca > Mg > P > S. Different recovery efficiency in cover crops can be useful in selecting cover crops with high recovery efficiency, which may be beneficial to succeeding crops in the cropping systems. The P × cover crops interactions were significant for soil extractable Ca²⁺, P, cation exchange capacity (CEC), Ca saturation, Ca/K ratio, and K/Mg ratio, indicating that cover crops change these soil property differently under different P levels. Thus, cover crops selection for different P levels is an important strategy for using cover crops in cropping systems in Brazilian Oxisols. Optimal values of soil pH, soil Ca and Mg contents, hydrogen (H) + aluminum (Al), P, CEC, base saturation, Ca saturation, Mg saturation, and K saturation were established for tropical cover crops grown on an Oxisol.     

Light Intensity Effects on Growth and Micronutrient Uptake by Tropical Legume Cover Crops

ABSTRACT

Cover crops are important components of a sustainable crop-production system in plantation crops such as cacao (theobroma cacao), coffee (Coffee arabica), oil palm (Elaeis Spp.), and banana (Musa Spp.). Optimal growth of cover crops in plantation agriculture is determined by adaptability of crop species, light intensity reaching their leaf canopies, and their nutrient-use efficiencies, including those of micronutrients. An experiment was conducted in a climatically controlled growth chamber to evaluate the influence of levels of light intensity on growth and micronutrient [boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn)] uptake parameters in legume cover crops. Two photosynthetic photon flux density (PPFD, 200 and 400 μmol m^?2 s^?1) light treatments were imposed on nine legume species (joint vetch (Aeschynomene americana), sunhemp (Crotalaria juncea L.), Crotalaria rchroleuca, showy crotalaria (crotalaria spectabilis), hairy indigo (Indigofera hirsute L.), lab-lab (Lablab purpureus), sesbania (Sesbania microcarpa), Brazilian stylo (Stylosanthes guianensis), and cowpea (Vigna unguiculata)). Overall, light intensity significantly affected growth, micronutrient uptake, and use-efficiency ratios; with few exceptions, interactions between cover crop species and PPFD were also significant. Such PPFD × crop species interactions show that the cover crops used in this study differed in growth and nutrient-uptake parameters under the conditions imposed. Sunhemp, cowpea, sesbania, and lab-lab species were superior in producing shoot dry weight and in nutrient accumulation compared with other species at lower as well as at higher PPFD levels. Interspecific differences in nutrient influx and transport were observed. Influx and transport of micronutrients was in the order Mn > B > Fe > Zn > Cu. Overall, growth, nutrient uptake, and use-efficiency ratios were higher at higher PPFD than at lower PPFD. Results of this study indicate that the use of proper crop species at adequate light intensities is an important component of successful cultivation of cover crops in plantation agriculture.     

Nutrient Uptake in Dry Bean Genotypes

Dry bean is an important legume for human consumption in South America. A greenhouse experiment was conducted to evaluate uptake and use efficiency of macro- and micronutrients by six dry bean genotypes at two P levels (25 and 200 mg kg^?1 soil). Shoot dry weight and grain yield varied significantly among genotypes and significantly increased with increasing phosphorus (P) levels. Grain harvest index (GHI) and 100-grain weight also differ significantly among genotypes and significantly increased with the increasing P levels. Based on grain yield efficiency index (GYEI), genotypes were classified as efficient and inefficient. The most efficient genotype was CNFP 10104, and inefficient genotypes were CNFP 10103 and CNFP 10120. Number of pods per plant and number of seeds per pod increased significantly with the addition of 200 mg P kg^?1 of soil compared to the low level of P (25 mg P kg^?1). Similarly, nitrogen (N), P, calcium (Ca), magnesium (Mg), sulfur (S), zinc (Zn), copper (Cu), and manganese (Mn) concentrations and uptake in the shoot and grain also significantly varied among genotypes. Uptake of macro- and micronutrients was greater under the greater P rate compared to the low P rate. This may be related to greater shoot or grain yield at 200 mg P kg^?1 soil compared to 25 mg P kg^?1 of soil.     

Nutrient Uptake and Use Efficiency of Dry Bean in Tropical Lowland Soil

Dry bean is an important source of protein for the population of South America, and yield of this legume is very low in this continent. Knowledge of nutrient uptake and use efficiency of a crop is fundamental to improve yield. A greenhouse experiment was conducted to evaluate growth, nutrient uptake, and use efficiency of dry bean (Phaseolus vulgaris L., cv. BRS Valente) during the growth cycle. Plant samples were collected at 15, 30, 45, 60, 73, and 94 days after sowing. Root dry weight, maximum root length, shoot dry weight, and number of trifoliates were significantly increased in a quadratic fashion with the advancement of plant age. Root dry weight and number of trifoliates had significant positive association with shoot dry weight. Uptake of nutrients in the grain was in the order of nitrogen (N) > potassium (K) > calcium (Ca) > magnesium (Mg) > phosphorus (P) > iron (Fe) > manganese (Mn) > zinc (Zn) > copper (Cu). Hence, it can be concluded the N requirements for bean is greatest and Cu is minimal compared to other essential nutrients for grain yield. Uptake efficiency for root, shoot, and grain production was in the order of P > Mg > Ca > K > N > Cu > Zn > Mn > Fe. The greatest P-use efficiency among macro- and micronutrients can be considered a positive aspect of mineral nutrition of bean, because recovery efficiency of P in acidic Inceptsols is less than 20%.     

Yield and Yield Components of Dry Bean Genotypes as Influenced by Phosphorus Fertilization

Dry bean is an important legume for South American population, and phosphorus (P) deficiency is the most yield-limiting nutrient for crop production in South American soils. A greenhouse experiment was conducted with the objective of evaluating influence of P fertilization on grain yield and yield components of 30 dry bean genotypes. The P levels used were 0 mg P kg^?1 (natural level of the soil) and 200 mg P kg^?1 applied with triple superphosphate fertilizer. Yield and yield components were significantly influenced with P as well as genotype treatments. The P?×?genotype interactions were significant for yield as well as yield components, indicating different responses of genotypes at two P levels. Root dry weight and maximum root length were also significantly increased with the addition of P fertilization. There were also significant differences among the genotypes in the growth of root system. Based on grain yield efficiency index (GYEI), genotypes were classified as P efficient, moderately efficient, and inefficient. Among 30 genotypes, 17 were classified as efficient, 12 were classified as moderately efficient, and 1 was classified as inefficient. Yield components such as pods per plant and seeds per pod were having significant positive association with grain yield. In addition, grain harvest index (GHI) was also having significant linear association with grain yield. Hence, it is possible to improve grain yield of dry bean in Brazilian Oxisol with the addition of adequate rate of P fertilization as well as use of P-efficient genotypes.     

ROOT GROWTH OF UPLAND RICE GENOTYPES AS INFLUENCED BY NITROGEN FERTILIZATION

The plant root system is an important organ which supplies water and nutrients to growing plants. Information is limited on influence of nitrogen fertilization on upland rice root growth. A greenhouse experiment was conducted to evaluate influence of nitrogen (N) fertilization on growth of root system of 20 upland rice genotypes. The N rate used was 0 mg kg^?1(low) and 300 mg kg^?1(high) of soil. Nitrogen X genotype interactions for root length and root dry weight were highly significant (P < 0.01), indicating that differences among genotypes were not consistent at two N rates. Overall, greater root length, root dry weight and tops-roots ration were obtained at an N fertilization rate of 300 mg kg^?1compared with the 0 mg N kg^?1soil. However, genotypes differ significantly in root length, root dry weight and top-root ratio. Nitrogen fertilization produced fine roots and more root hairs compared with absence of N fertilizer treatment. Based on root dry weight efficiency index (RDWEI) for N use efficiency, 70% genotypes were classified as efficient, 15% were classified as moderately efficient and 15% were classified as inefficient. Root dry weight efficiency index trait can be incorporated in upland rice for improving water and nutrient efficiency in favor of higher yields.     

LOWLAND RICE GROWTH AND DEVELOPMENT AND NUTRIENT UPTAKE DURING GROWTH CYCLE

Rice is a staple food for more than 50% of the world's population and the majority of the global rice is produced from a lowland ecosystem. A greenhouse experiment was conducted with the objective to study lowland rice (cv. ‘BRSGO Guara’) growth, development, and nutrient uptake patterns during growth cycle. Growth observations and plant analysis were performed at initiation of tillering (IT), active tillering (AT), panicle initiation (PI), booting (B), flowering (F) and physiological maturity (PM). Plant height, number of leaves per culm, number of tillers per plant and maximum root length and root dry weight increased in a quadratic fashion with increasing plant age. Similarly, shoot dry weight increased linearly during growth cycle of the cultivar ‘BRSGO Guara’. Concentration and accumulation of most of the macronutrients and micronutrients responded with a quadratic trend with the advancement of plant age. Plant growth parameters were significantly associated with shoot dry weight plus grain yield. Similarly, nutrient accumulation had a significant correlation with shoot dry weight plus grain yield, which indicated the importance of these nutrients in the lowland rice production.     

Copper-Use Efficiency in Dry Bean Genotypes

Copper (Cu) is an essential micronutrients and its deficiency has been reported in many crops including dry bean. A greenhouse experiment was conducted to evaluate thirty dry bean genotypes (G) for Cu-use efficiency. The Cu levels used were low (natural soil level) and adequate [10 mg Cu kg^?1 soil, applied with copper sulfate (24 percent Cu)]. Straw yield, seed yield, number of pods per plant, seed per pod, seed harvest index (SHI), maximum root length (MRL), and root dry weight (RDW) were significantly affected by Cu and genotype treatments. The Cu × G interactions were also significant for these traits, indicating variation in genotype responses with the variation in Cu levels. Based on seed yield efficiency index (SYEI), genotypes were grouped in three classes: Cu efficient, moderately Cu efficient, and Cu inefficient. Fifty-three percent of the genotypes were classified as efficient, 40 percent were classified as moderately efficient, and 7 percent were classified as inefficient in Cu-use efficiency.     

Role of Cover Crops in Improving Soil and Row Crop Productivity

Abstract

Cover crops play an important role in improving productivity of subsequent row crops by improving soil physical, chemical, and biological properties. The objective of this article is to review recent advances in cover crops practice, in the context of potential benefits and drawbacks for annual crop production and sustained soil quality. Desirable attributes of a cover crop are the ability to establish rapidly under less than ideal conditions, provide sufficient dry matter or soil cover, fix atmospheric nitrogen (N), establish a deep root system to facilitate nutrient uptake from lower soil depths, produce organic matter with low‐residue carbon/nitrogen (C/N) ratio, and absence of phytoxic or allelopathic effects on subsequent crops. Cover crops can be leguminous or nonleguminous. Leguminous cover crops provide a substantial amount of biologically fixed N to the primary crop, as well as ease of decomposition due to their low C/N ratio. Legume cover crops also possess a strong ability to absorb low available nutrients in the soil profile and can help in increasing concentration of plant nutrients in the surface layers of soil. Some nonleguminous cover crops having high N scavenger capacity compared with leguminous crops and sometimes, the growth of these scavenging grass cover crops is limited by N deficiency, growing grass/legume mixtures appears to be the best strategy in obtaining maximum benefits from cover crops.     

Effects of Soil-Applied Materials on the Dry Weight and Boron Uptake of Maize Shoots (Zea Mays L.) Under High Boron Conditions

High concentrations of boron (B) in the soil, reduces plant growth, crops’ yield and quality. Regarding such problem, synergistic and antagonistic relations between the nutrients can be used to ameliorate the B toxicity. Therefore, a greenhouse experiment was conducted to evaluate effects of soil-applied zinc (Zn), nitrogen (N), calcium (Ca), lime (CaCO₃), potassium (K), humic acid (HA), and humus on the dry weight and B uptake of maize shoots (Zea mays L.) under high-B containing soil conditions. Increasing doses of B (0, 2.5, 5, and 10 mg kg^?1 B) were applied to soil as borax (Na₂B₄O₇10H₂O), and boric acid (H₃BO₃). Positive correlations were found between B doses and the uptake amounts (r = 0.934**; – 0.964**). However, the correlations between the dry weight and B doses (r = ?0.314**; – r = ?0.495**) and between the dry weight and the uptake amounts (r = ?0.294*; – r = ?0.497**) were negative. Among the materials, Zn and humus exhibited positive correlations with dry weight values (r = 0.249*; r = 0.525**), and an effective increase (p < 0.01) in the dry weight amounts of maize shoots was observed under toxic B conditions.     

Phosphorus Nutrition of Upland Rice,Dry Bean,Soybean, and Corn Grown on an Oxisol

Rice, dry bean, corn, and soybean are important food crops. Phosphorus (P) deficiency is one of the most yield-limiting factors for these crops grown on highly weathered Brazilian Oxisols. Four greenhouse experiments were conducted to determine P requirements of these four crops. The P levels used were 0, 50, 100, 200, and 400 mg kg^?1. Growth, yield, and yield components evaluated of four crop species were significantly increased with the application of P fertilization. Most of the responses were quadratic in fashion when the P was applied in the range of 0 to 400 mg kg^?1. Maximum grain yield of upland rice was obtained with the application of 238 mg P kg^?1 of soil, maximum dry bean grain yield was obtained with the application of 227 mg P kg^?1 of soil, and maximum grain yield of soybean was obtained with the application of 224 mg P kg^?1 of soil. Maximum shoot growth of corn was obtained with the addition of 323 mg P kg^?1 of soil. Most of the growth and yield components had significant positive association with grain yield or shoot dry weight. Phosphorus concentration and uptake were greater in the grain compared to straw in upland rice and dry bean plants. Overall, P-use efficiencies decreased with increasing P rates.     

Dry Bean Genotypes Evaluation for Zinc-Use Efficiency

Dry bean is an important legume for human consumption worldwide. Low soil fertility, including zinc (Zn) deficiency, is one of the main factors limiting yield of this legume in South America, including Brazil. The objective of this study was to evaluate 30 dry bean genotypes for zinc (Zn)–use efficiency. The Zn rates used were 0 mg Zn kg^?1 (low) and 20 mg Zn kg^?1 (high) of soil. Grain yield, straw yield, number of pods, hundred-seed weight, number of seeds per pod, maximum root length, and rood dry weight were significantly affected by Zn and genotype treatments. The Zn × genotype interactions were also significant for growth, yield, and yield components, indicating that some genotypes were highly responsive to the Zn application while others were not. Based on seed yield efficiency index (SYEI), genotypes were classified as efficient, moderately efficient, and inefficient in Zn-use efficiency. Most efficient genotypes were CNFP 10104, BRS Agreste, BRS 7762 Supreme, CNFC 10429, BRS Estilo, CNFC 10467, BRS Esplendor, and BRS Pitamaba. The most inefficient genotype was BRS Executive. Remaining genotypes were moderately efficient in Zn-use efficiency.     

Biomass Yield and Nutrients Concentration in Shoot Dry Weight of Winter Cover Crops for No-Tillage System

The aim of this study was to identify the cutting time for winter cover crops used as green manure in no-tillage systems that results in the highest dry weight yield (DWY) and nutrient accumulation. We tested Avena strigosa, Secale cereale, Vicia sativa, Raphanus sativus, and Lupinus albus, in five management times, determining the fresh weight yield (FWY), DWY, and the chemical composition of the shoot tissue. The highest FWY was obtained using R. sativus and L. albus. At 145 days after sowing; these species also had the highest DWYs, over 15 t ha^?1. L. albus and S. cereale had the highest carbon to nitrogen (C:N) ratio (60:1). The nutrient content of most crops decreased over time. However, the accumulation of nutrients increased over time, especially for R. sativus. L. albus had the highest level and manganese (Mn) accumulation, while the zinc (Zn) and cooper (Cu) accumulation was highest in A. strigosa, and that of boron (B) was highest in S. cereale. Thus, R. sativus provided the best soil cover among the species tested, due to its high biomass yield and greater nutrient cycling.     

Arbuscular mycorrhizal fungi-mediated nitrogen transfer from vineyard cover crops to grapevines

Cover crops are often planted in between vineyard rows to reduce soil erosion, increase soil fertility, and improve soil structure. Roots of both grapevines and cover crops form mutualistic symbioses with arbuscular mycorrhizal (AM) fungi, and may be interconnected by AM hyphae. To study nutrient transfer from cover crops to grapevines through AM fungal links, we grew grapevines and cover crops in specially designed containers in the greenhouse that restricted their root systems to separate compartments, but allowed AM fungi to colonize both root systems. Leaves of two cover crops, a grass (Bromus hordeaceus) and a legume (Medicago polymorpha), were labeled with 99 atom% ¹⁵N solution for 24 h. Grapevine leaves were analyzed for ¹⁵N content 2, 5, and 10 days after labeling. Our results showed evidence of AM fungi-mediated ¹⁵N transfer from cover crops to grapevines 5 and 10 days after labeling. N transfer was significantly greater from the grass to the grapevine than from the legume to the grapevine. Possible reasons for the differences between the two cover crops include lower ¹⁵N enrichment in legume roots, higher biomass of grass roots, and/or differences in AM fungal community composition. Further studies are needed to investigate N transfer from grapevines to cover crops and to determine net N transfer between the two crops throughout their growing seasons, in order to understand the significance of AM fungi-mediated interplant nutrient transfers in the field.