Forage Dry Weight Research Articles

PRODUCTIVITY OF ELEPHANT GRASS (Pennisetum purpureum) PLANTED WITH LEGUMINOSE AT VARIOUS DOSAGES OF BIOORGANIC FERTILIZER


 
 
 The purpose of this study was to determine the productivity of elephant grass (Pennisetum purpureum) planted with leguminosae at various doses of bioorganic fertilizers. This study used a completely randomized design with two factorial patterns. The first factor was the type of leguminosae (T= without leguminosae; R= Arachi pintoi; L= Alysicarpus vaginalis; and the second factor was the dose of bioorganic fertilizer (D0= 0 kg Nha-1; D1= 100 kg Nha-1; D2= 200 kg Nha-1; and D3= 300 kg Nha-1) There were 12 treatment combinations, each treatment was repeated 5 times so that it consisted of 60 experimental units. The observed variables included growth, yield and growth characteristics variable. The results showed that there was no interaction between leguminous species and fertilizer dosage, both leguminous species only increased leaf area per pot, bioorganic fertilizer D1 and D2 doses tended to increase, while D3 dose increased leaf dry weight, total forage dry weight, and leaf area per pot of elep- hant grass (Pennisetum purpureum). It was concluded that the type of leguminous did not affect the productivity of elephant grass, the dose of bioorganic fertilizer increased crop yields, the highest yields at a dose of 300 kg Nha-1 bioorganic fertilizer.
 
 

Effect of Nitrogen Fertilizer on the Quality of Rhodes Grass (Chloris gayana. L. kunth.) Cultivars

A field experiment was conducted in the Demonstration Farm of the Faculty of Agricultural Studies, Sudan University of Science and Technology, during the season (2006/2007) to investigate the effect of nitrogen fertilizer on crude protein, fiber, ash content, ether extract, nitrogen free extract and metabolizable energy of Rhodes grass (Chloris gayana L.) cultivars. Four cultivars of Rhodes grass (Katambora, Callide, Boma and Finecut) were used in this study. Four levels of Nitrogen fertilizers (0, 40, 60 and 80 kg N/ha) were used. The treatments were arranged in a split-plot with four replications. Nitrogen applications lead to insignificant increase in crude protein for all cultivars except for Katambora cultivar. The results revealed that, crude fiber insignificantly affected by nitrogen applications for the cultivars Callide and Boma. Whereas; the cultivars Katambora and Finecut were significantly affected. Ether extract significantly affected by nitrogen application in all cultivars. The results showed that, ash was not affected by nitrogen levels for all cultivars except for cultivar Callide. Nitrogen free extract was significantly affected by nitrogen levels for all cultivars. Moreover, the metabolizable energy was significantly affected by nitrogen applications in all cultivars except cultivar Katambora. It can be concluded that, the best cultivars in the terms of forage Dry Weight, Crude Protein and Nitrogen Free Extract were Finecut, Callide, Katambora and Boma respectively with added fertilizer (80 kg N /ha).

Response of soybean (Glycine max L.) that was applied by various liquid organic fertilizer in climate change at acid soil

Acidic soils are formed from rapid climate change. Acid soils have problems in it, among others; high levels of Al, Fe, and Mn and the unavailability of elements P and N for staple crops. Indonesia imports almost 70% of its domestic requirement. The purpose of this study was to determine the response of soybean plants that were given various types of liquid organic fertilizer (LOF) to climate change in acid soils. Experiments have been carried out in acid soil in the Kuranji area of Padang City. Materials needed include; Mutiara-1 seed. The lime and LOF trials were arranged in a completely randomized design (CRD), with 9 treatments namely; without calcification and without LOF (A); give lime equivalent to 1 x Exchangeable Al and without LOF (Control) (B); Crocober (C); Crocoberma (D); Crocoberderma (E); Titocroco (F); Titocrocoma (G); (H); Trichoderma harzianum (I). The observational data were analyzed statistically by using an F level of 5% significance level if the treatment had a significant effect, it was followed by a LSD test of 5% significance level. Observation parameters include; agronomic, pH soil. Experimental results established that given of dolomite lime can increase soil pH, Titocrocoma LOF accompanied by liming gives the best effect on soybean varieties Mutiara-1 at vegetative stadium, produces 3.45 Mg ha−1 forage dry weight equivalent to107,64 kg N ha−1 or 618,93 kg ha−1 crude protein.

PRODUCTIVITY OF PINTO BEANS (Arachis pintoi) WITH DIFFERENT TYPES AND DOSAGE OF ORGANIC FERTILIZER

The study aims to determine the productivity of pinto beans (Arachis pintoi) which is fertilized with differenttypes of organic fertilizer including its dosage. The study was conducted by using a completely randomized design(CRD) within two patterns of factors. Firstly, organic fertilizers are cow dung (S) and chicken manure (A). Secondly,dosages without fertilizer (D0), 15 tons/ha dosages (D1), 20 tons/ha dosages (D2), dosage of 25 tons/ha (D3); anddosage of 30 tons/ ha (D4) of organic fertilizers. The variables observed were plant height, number of branches,number of leaves, leaf dry weight, stem dry weight, total forage dry weight, leaf areat and leaf dry weight ratio withstem dry weight. The results showed no interaction between the type and dosage of fertilizer in which the growthand production of pinto beans (Arachis pintoi) gave the same results by fertilizing with 25-30 tons/ha dosagesof chicken manure. It can be concluded that increasing the productivity of pinto beans (Arachis pintoi) can befertilized with 25-30 tons/ha dosages of chicken manure

EFEK SUBSITUSI PUPUK UREA DENGAN PUPUK BIO SLURRY TERHADAP PRODUKTIVITAS RUMPUT BENGGALA (Panicum maximum cv. Trichoglume)

This experiment to determine the effect of substitution of urea fertilizer with bio slurry fertilizer on productivity of Panicum maximum cv. Trichoglume grass. The experiment was conducted in a greenhouse for 3 months. The design was used completely randomized design (CRD), with seven treatments and each treatment repeated five times. The treatment was dosage of 200 urea kg/ha (A); 150 kg urea/ha + 10 tons cow bio slurry /ha (B); 100 kg urea/ha + 20 tons cow bio slurry/ha (C); 50 kg urea/ha + 30 tons cow bio slurry/ha (D); 150 kg urea/ha + 10 tons pig bio slurry/ha (E); 100 kg urea/ha + 20 tons pig bio slurry/ha (F); 50 kg urea/ha + 30 tons pig bio slurry/ha (G). Variables observed were plant height, number of tillers, number of branches, number of leaves, leaf dry weight, stem dry weight, total forage dry weight, leaf area per pot, and leaf dry weight ratio with stem dry weight. The results showed that the effectiveness of urea fertilizer substitution with pig bio slurry gave the best growth and production of grass Panicum maximum cv. Trichoglume, where treatment (G) with substitution of 50 kg urea/ha + 30 tons pig bio slurry/ha gave the highest yield. It can be concluded increasng of growth and production of grass Panicum maximum cv. Trichoglume can be substituted with 50 kg urea/ha + 30 tons pig bio slurry/ha.
 Keywords: substitution, urea, bio slurry, productivity, Panicum maximum

PRODUCTIVITY OF GAMAL (Gliricidia sepium) AND INDIGOFERA (Indigofera zollingeriana) FORAGE ON DIFFERENT DOSAGE OF BIOORGANIC FERTILIZER

This study aims to obtain a study of the productivity of Gliricidia sepium and Indigofera zollingeriana plants which are given various dosage of bioorganic fertilizer. This study used a completely randomized design of factorial patterns of two factors: the first factor was the type of plant (G = Gamal; I = Indigofera) and the second factor was the dosage of bioorganic fertilizer: D0 = without fertilizer; D1 = 5 tons ha-1; D2 = 10 tons ha-1; D3 = 15 tons ha-1; D4 = 20 tons ha-1; D5 = 25 tons ha-1; and D6 = 30 tons ha-1, so there are 14 treatment combinations. Each treatment was repeated three times so that it consisted of 42 experimental units. The variables observed were plant height, leaf number, stem diameter, leaf dry weight, stem dry weight, total herbage dry weight, amount of chlorophyll, ratio of dry weight of leaf / stems, and leaf area per pot. The results showed that the productivity of Indigofera zollingeriana significant higher than Gliricidia sepium. The application of bioorganic fertilizer significantly increased plant height, leaf number, dry weight leaf, stem dry weight, total forage dry weight, amount of chlorophyll, and leaf area per pot, and the highest yield at 30 tons/ha. Based on the results of the study it can be concluded that the productivity of Indigofera zollingeriana is higher than Gliricidia sepium, bioorganic fertilizer increased plant productivity with the highest yield at 30 tons ha-1, and interaction only occurs in the leaf area per pot.
 Keywords: Indigofera zollingeriana, Gliricidia sepium, dosage of fertilizer, bioorganic fertilizer

PRODUKTIVITAS TANAMAN LEGUMINOSA (Centrocema pubescens DAN Clitoria ternatea) YANG DIPUPUK DENGAN PUPUK BIO SLURRY

This study aims at determining the productivity of legume fertilized with bio slurry. The study was conductedby using a complete randomized design (CRD) with two factors as factorial design. The first factor is the type oflegume plants, namely Centrocema pubescen and Clitoria ternatea. The second factor is the dosage of bioslurryfertilizer such as fertilizer as control; 10 tons/ha of bioslurry fertilizer; 20 tons/ha of bioslurry fertilizer; 30 tons/ha of bio slurry fertilizer. Variables observed were growth (plant height, number of tillers, and number of leaves);production variables (leaf dry weight, stem dry weight, root dry weight and total dry weight of forage); and growthcharacteristics (leaf area, leaf dry weight ratio of dry weight rod, and ratio of the total dry weight of forage with rootdry weight). The results showed that the bio-slurry fertilizer increase productivity and legume plants (Centrocemapubescen and Clitoria ternatea). The differences of 10-30 tons/ha bioslurry treatment significantly (P<0.05)increase number of tillers, number of leaves, total forage dry weight, dry weight of leaf, stem dry weight, root dryweight, leaf area, ratio of total dry weight of forage with roots and leaves with the stem ratio). It can be concludedthat higher productivity of legume plants species found significantly (P<0.05) on Clitoria ternatea with 30 tons/hadosages of bioslurry fertilizer as the best result.

Effect of Different Planting Pattern on Total Dry Matter Production and Maize Forage Quality in Maize (Zea Mays) and Cowpea (Vigna Sinensis) Intercropped As Whole-Crop Forage

Mixtures of cereals and legumes are used extensively for forage production. Maize (Zea mays) and cowpea (Vigna sinensis) monocultures as well as their mixture in three planting patterns (M1: alternate-row intercrop, M2: within-row intercrop, M3: mixed intercrop) were used to investigate on forage yield as well as the effect of intercropping on maize forage quality. The experiment was carried out as randomized complete block design with three replications. The results showed that intercropping systems had a significant effect on forage dry weight, where dry matter yield was increased by intercropping as compared with maize and cowpea sole crops. It was related with a higher consumption of environmental resources, such as photosynthetically active radiation and soil moisture, by intercropping. Maize forage quality in terms of crude protein was improved by intercropping. It was because of more nitrogen availability for maize in intercropping compared with its sole crop.

Adubação nitrogenada de sorgo granífero consorciado com capim em sistema de plantio direto

O objetivo deste trabalho foi avaliar o efeito do manejo da adubação nitrogenada sobre a cultura do sorgo granífero, cultivado solteiro e em consócio com capim-marandu e capim-mombaça, e determinar a produtividade de matéria seca das forrageiras, nos anos agrícolas 2003/2004 e 2004/2005, em plantio direto. Foi utilizado o delineamento experimental em blocos ao acaso, em arranjo fatorial 3x5, com quatro repetições. Os tratamentos consistiram de três sistemas de cultivo de sorgo granífero (solteiro e consorciado com capim-marandu ou capim-mombaça, na linha de semeadura) e cinco manejos de adubação nitrogenada: 30-70; 70-30; 50-50; 100-0; e 0-100 kg ha-1 de N, quantidades aplicadas na semeadura e na cobertura, respectivamente. O cultivo consorciado não afetou a nutrição nem a produtividade de grãos de sorgo. Apenas no primeiro ano de cultivo, o parcelamento 50-50 kg ha-1 de N proporcionou maior produtividade de grãos. O manejo da palhada interferiu no estabelecimento do sorgo no segundo ano de cultivo, e diminuiu a produtividade de grãos. As maiores doses de N aplicadas em cobertura elevaram a produtividade de matéria seca do capim-marandu e, as aplicadas em semeadura, a elevaram no capim-mombaça.

Abordagem bayesiana para avaliação da adaptabilidade e estabilidade de genótipos de alfafa

O objetivo deste trabalho foi propor uma abordagem bayesiana do método de Eberhart & Russell para avaliar a adaptabilidade e da estabilidade fenotípica de genótipos de alfafa (Medicago sativa), bem como avaliar a eficiência da utilização de distribuições a priori informativas e pouco informativas. Foram utilizados dados de um experimento em blocos ao acaso, no qual se avaliou a produção de massa de matéria seca de 92 genótipos. A metodologia bayesiana proposta foi implementada no programa livre R por meio da função MCMCregress do pacote MCMCpack. Para representar as distribuições a priori pouco informativas, utilizaram-se distribuições de probabilidade com grande variância; e, para representar distribuições a priori informativas, adotou-se o conceito de meta-análise, que se caracteriza pela utilização de informações provenientes de trabalhos anteriores. A comparação entre as distribuições a priori foi realizada por meio do fator de Bayes, com a função BayesFactor do pacote MCMCpack, que indicou a priori informativa como a mais adequada nas condições deste estudo.

Intercropping of Maize (Zea mays) and Cowpea (Vigna sinensis) as Whole-Crop Forage: Effect of Different Planting Pattern on Total Dry Matter Production and Maize Forage Quality

Mixtures of cereals and legumes are used extensively for forage production. Maize (Zea mays) and cowpea (Vigna sinensis) monocultures as well as their mixture in three planting patterns (M1: alternate-row intercrop, M2: within-row intercrop, M3: mixed intercrop) were used to investigate on forage yield as well as the effect of intercropping on maize forage quality. The experiment was carried out as randomized complete block design with three replications. The results showed that intercropping systems had a significant effect on forage dry weight, where dry matter yield was increased by intercropping as compared with maize and cowpea sole crops. It was related with a higher consumption consumption of environmental resources, such as photosynthetically active radiation and soil moisture, by intercropping. Maize forage quality in terms of crude protein was improved by intercropping. It was because of more nitrogen availability for maize in intercropping compared with its sole crop.

Estimation of Forage Production of <i>Acroceras macrum</i> from Meteorological Factors

Field experiments were conducted at Taiwan Livestock Research Institute Experimental Farm to measure the fresh and dry weights of forage production and plant height of nilegrass (Acroceras macrum Stapf) and to collect meteorological data during the growing seasons in 2002-2003. The accumulated values of daily mean air temperature (DMAT), precipitation (DP), evaporation (DE), irradiance (IR), and sunshine hours (DSH) during the growing periods of six seasons were calculated to correlate with plant height and forage production. Forage fresh weight was found linearly correlated with plant height (R2=0.786, P＜0.0001) and forage dry weight (R2=0.903, P＜0.0001). Changes of both forage fresh weight and plant height were shown corresponding to the accumulated values of DMAT, DP, DE, IR, and DSH. By multiple linear regression analyses, estimation of fresh-based forage production may be improved by a three-variable linear regression model (R2=0.825, P＜0.0001) from DMAT, DP and IR, while plant height may be best estimated by a two-variable model (R2=0.815, P＜0.0001) from DP and DE. When validating the models with another set of data from different seasons, models gave over-predicted values, particularly fresh-based forage production. Results suggest that more data need to be collected from diversified environments to establish a model for a better estimation.

Variation in symbiotic characters of alfalfa cultivars inoculated with Sinorhizobium meliloti strains

In this paper the interactive effects of different Sinorhizobium meliloti strains and alfalfa cultivars on the host plant growth and nodulation were evaluated. In the experiments, six alfalfa cultivars (Giza-1, Ismailia-94, Kometa, Radius, Luzella and Legend) as well as five S. meliloti strains (ARC-1, ARC-2, A2, TAL and L5-30) were included. The alfalfa cultivars, Giza-1 and Ismailia-94, exhibited the highest average dry forage weight with all studied strains. Generally, plants inoculated with the S. meliliti ARC-2 strain produced significantly higher shoot and root dry weights over all evaluated cultivars. The strain L5–30 of S. meliloti produced the highest nodule number with all the studied alfalfa cultivars whereas, among tested cultivars, N2-fixing Luzella showed the highest nodulation with the majority of rhizobial strains. Analysis of correlation coefficients for the studied alfalfa-rhizobium associations revealed positive and significant relationships of shoot dry weight with root dry weight. In contrast, nodule number per plant correlated negatively with forage dry weight of plants. It was also found that nodule number per plant is not a promising trait with which to select the most effective N2-fixing rhizobium-legume systems; selection of such symbiotic associations should be done on the basis of shoot and root dry weights.

Produção e perfilhamento de Brachiaria decumbens Stapf. em função de doses de enxofre

O experimento foi realizado em casa-de-vegetação em Piracicaba, São Paulo, no período de outubro a dezembro de 1996, com Brachiaria decumbens Stapf. cv. Basilisk cultivada em solução nutritiva e utilizando sílica como substrato. Foi empregado o delineamento de blocos completos ao acaso, com quatro repetições. O primeiro corte das plantas foi efetuado 40 dias após transplante para os vasos, e o segundo corte 30 dias após o primeiro. Foram avaliadas oito doses de enxofre (0; 2; 4; 16; 32; 48; 64 e 80 mg L-1) na produção de matéria seca e no número de perfilhos. As doses de enxofre proporcionaram aumentos na produção de matéria seca da parte aérea e das raízes do capim-braquiária e influenciaram o número de perfilhos no segundo crescimento dessa forrageira.

Response of a white clover indicator system to tropospheric ozone at eight locations in the United States

A white clover (Trifolium repens L.) system using measured biomass to indicate effective concentrations of tropospheric ozone (O3) has been developed. The system utilizes the relative response of an O3-sensitive clone (NC-S) and an O3-resistant clone (NC-R) grown in 15-liter pots. Forage (leaves, stems and flowers) is cut, dried, and weighed at 28-day intervals. Forage dry weight ratios (NC-S/NC-R) for individual or multiple harvests indicate O3 concentrations during growth. In, 3 years of testing in open-top field chambers at Raleigh, North Carolina, O3 always decreased growth of NC-S more than that of NC-R and the NC-S/NC-R ratio routinely decreased as the O3 concentration increased. A national field test was performed in 1993 and 1994 to determine if the clover system can account for effects of climatic variables on clover growth per-se, and if climatic variables affect the relative response of the two clones to O3. Eight locations (Corvallis, Oregon; Kennedy Space Center, Florida; Delaware, Ohio; Amherst, Massachusetts; Blacksburg, Virginia; Raleigh, North Carolina; Riverside, California; San Bemardino mountains, California) provided large differences in O3 concentrations and climate. The NC-S/NC-R forage ratios for three consecutive 28-day growth periods for each year as related to the mean 12 hour per day O3 concentrations are presented in this manuscript. Ratios were generally highest where mean O3 concentrations were lowest (Oregon and Florida), lowest where mean O3 concentrations were highest (both California locations), and intermediate at other locations.

Predicted and Actual Yield and Nitrogen Concentration of Alfalfa in Different Nitrogen Environments

Glasshouse studies with alfalfa (Medicago sativa L.) have shown that improving both forage dry weight (DW) and N concentration (NC) requires selection under N2‐ and NH4NO3‐dependent conditions. The objectives of the present study were to (i) determine genetic variances of forage DW and NC in the field under different levels of N fertilization, (ii) use the genetic variances to predict selection gain for DW and NC at each level of N, (iii) select for increased DW and NC under field conditions and compare actual gains with predicted values, and (iv) compare the efficiencies of field and glasshouse selections for DW and NC. Twenty‐five randomly chosen half‐sib families from ‘Moapa 69’ were planted in each of 2 yr at four locations using a split‐plot design with four levels of N fertilizer (0, 33, 66,100 kg N ha‐1). Forage DW and NC of plants were measured at each location, and individual plants were selected at one location for both DW and NC in each N level using independent culling levels. Genetic variance and predicted gain per cycle for DW were maximized with 100 kg N ha‐1 (118 g kg‐1), while those for NC were greatest without N fertilizer (64 g kg‐1). Selection for either DW or NC alone under these N levels predicted negative correlated responses in the unselected character. Theoretical selection response using independent culling levels for DW followed by NC was greatest under the 33 kg N ha‐1 fertilization level (197 g kg‐1 and 61 g kg‐1 per cycle, respectively). Results of actual selection tests agreed closely with predicted gains and indicate that effective selection for forage DW and NC can be conducted in the field with a low level of N fertilization.

Bristly Starbur (Acanthospermum hispidum) Interference in Peanuts (Arachis hypogaea)

The effects of bristly starbur interference with peanuts were studied from 1980 through 1983 on a Dothan sandy loam (Plinthic Paleudults). Peanut seed yields, which included kernels plus hulls, were reduced as bristly starbur densities increased from 2 to 64 plants/7.5 m of row. Full-season interference from 8, 16, 32, and 64 bristly starbur plants/7.5 m of row reduced peanut seed yields 14, 26, 43, and 50%, respectively. The seed yield of peanuts maintained weed free for 6 weeks after crop emergence was reduced by no more than 3% compared to peanuts maintained weed free for the entire season. Weed interference for 2 weeks after crop emergence reduced seed yield by an average of 4% over the 3-yr period, based on prediction equations. Bristly starbur interference for 13 weeks after crop emergence reduced peanut forage dry weight yield by 54%. Similarly, peanut interference for 13 weeks after emergence reduced bristly starbur forage dry weight yield by 32%. Bristly starbur density in the forage dry weight studies averaged 35/7.5 m of row. These bristly starbur were confined to a 35-cm band over the drill. Peanut density averaged 72/7.5 m of drill.

Rangeland Vegetation Response Following Control of Brownspine Pricklypear (Opuntia phaecantha) with Herbicides

Brownspine pricklypear (Opuntia phaecantha Engelm. & Bigel.) was effectively controlled within 2 yr following application of a 1:1 mixture of 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] and picloram (4-amino-3,5,6-trichloropicolinic acid) at a rate of 0.6 kg ae/ha. Brownspine pricklypear canopy cover and dry weight declined from approximately 23% and 3800 kg/ha to 8% and 1600 kg/ha, respectively. No significant difference in total herbaceous forage dry weight was found between plants growing inside brownspine pricklypear canopy areas and plants growing outside the canopy areas. Differences between areas in species composition were significant in that cool-season grasses dominated the canopy area of the brownspine pricklypear colonies while warm-season grasses dominated the area outside the canopy. Control of brownspine pricklypear will enhance livestock carrying capacity of rangeland in the Rolling Plains of Texas by increasing forage availability but not forage production.

Alfalfa Stem and Leaf Growth during Water Stress1

AbstractAlfalfa (Medicago sativa L.) requires irrigation in semiarid and arid regions and improved yields often result from irrigation in subhumid and humid areas. Despite the importance of optimizing water management for alfalfa leaf and stem growth, no field study has been reported which relates alfalfa leaf expansion or stem extension to plant water deficits. The objective of our research was to determine how leaf expansion, stem elongation, and stomatal response of alfalfa related to the water potential in alfalfa, field‐grown on Plainfield loamy sand (mixed, mesic Typic Udipsamment). Periodic measurements of alfalfa stem extension and leaf expansion (area derived from length and width measurements) were related to leaf water potential (ΨL) measured with a pressure chamber, soil matric potential (Ψm, measured with tensiometers, and stomatal conductance measured with porometers. For wellwatered alfalfa, expansion curves of individual leaves were sigmoid‐shaped, while internode extensions were nearly exponential with time through about 95% of the total extension. The primary leaf attached at the top of an internode expands to nearly full size before the internode begins rapid extension. The growth of individual leaves and internodes collectively results in nearly constant rates of leaf expansion and stem extension during vegetative regrowth. When Ψm at 30 cm decreased to −0.35 bar, afternoon ΨL decreased to about −8 bars, about 2 bars below irrigated alfalfa, and both the growth rate (GR) and relative growth rate (RGR) of stressed leaves and stems were significantly less (p < 0.1) than well‐watered leaves and stems. In stressed treatments, wilting, gray‐green canopy color, decreased afternoon stomatal conductance, and a 50% decrease in RGR as compared to irrigated treatments resulted when afternoon ΨL decreased to about −15 bars even though Ψm exceeded −0.1 bar at 90 and 150 cm. Alfalfa extracted 85% of its total water from the 1st meter of soil prior to the onset of decreased afternoon stomatal conductance, but nearly equal percentages from each of the top 2 m of soil afterward. Little shoot growth occurred when ΨL dropped below −10 bars. Development of water stress 2 weeks after cutting reduced alfalfa leaf size, internode length, and dry matter production, but not leaf and internode number or stem density. The percentage of total forage dry weight in leaves (LPDW) decreased linearly with stem height resulting in higher LPDW and a better quality forage in stress‐stunted forage. Cool night temperatures limited growth of well‐watered alfalfa.

Availability of Rock Phosphate as Measured by an Acid Tolerant Pasture Grass and Extractable Phosphorus1

AbstractAs agricultural development intensifies in tropical countries and as costs of superphosphate production increase, the need for further evaluation of rock phosphates has become apparent. An acid tolerant pasture grass (Brachiaria decumbens Stapf.) was used to evaluate the initial and residual (3 years) availability of P from several phosphate materials. A field study was conducted on a Typic Haplustox of the Cerrado of Central Brazil. Initial availability of P supplied as normal superphosphate, Hyperphosphate, Thermalphosphate, and North Carolina rock phosphate was similar when the soils were not limed (pH = 4.3, Al = 1.4 meq/100g). Where lime had been added and pH was increased to 5.4 the P in Hyperphosphate and N.C. rock phosphate was initially less available than P added as superphosphate and Thermalphosphate. After 10 months of contact, lime no longer significantly depressed P availability in these relatively soluble rock phosphates as measured by forage dry weight. The P in the other phosphate rock of low citric acid solubility, Araxá, was virtually unavailable during the 3 months after application. However, within 13 months, maximum forage yields were attained where this material had been applied to unlimed soil and at 25 months maximum yields were obtained on both limed and unlimed soil. Higher rates of Araxá material were required to obtain maximum yields than with normal superphosphate. Forage yields were 2 to 4 times greater where superphosphate was surface applied each year than where similar amounts were incorporated prior to planting. A comparison of extractant methods for soil P indicated that highly acidic extractants (e.g., 0.05 N HC1 + 0.025 N H2SO4) overestimated available P where rock phosphate had been applied. Where superphosphate or rock phosphate had been applied, P availability was better assessed by extractants such as 0.5 M NaHCO3 and Bray 1. The results emphasize the need to supplement laboratory and short‐term studies with long‐term evaluations of P materials with acid tolerant perennial crop species available in tropical countries.