Lablab Purpureus Cv Research Articles

Phylogenetic analysis of phytochrome A gene from Lablab purpureus (L.) Sweet

BackgroundPhytochromes are the best characterized photoreceptors that perceive Red (R)/Far-Red (FR) signals and mediate key developmental responses in plants. It is well established that photoperiodic control of flowering is regulated by PHY A (phytochrome A) gene. So far, the members of PHY A gene family remains unexplored in Lablab purpureus, and therefore, their functions are still not deciphered. PHYA3 is the homologue of phytochrome A and known to be involved in dominant suppression of flowering under long day conditions by downregulating florigens in Glycine max. The present study is the first effort to identify and characterize any photoreceptor gene (PHYA3, in this study) in Lablab purpureus and decipher its phylogeny with related legumes. ResultsPHYA3 was amplified in Lablab purpureus cv GNIB-21 (photo-insensitive and determinate) by utilizing primers designed from GmPHYA3 locus of Glycine max. This study was successful in partially characterizing PHYA3 in Lablab purpureus (LprPHYA3) which is 2 kb longer and belongs to exon 1 region of PHYA3 gene. Phylogenetic analysis of the nucleotide and protein sequences of PHYA genes through MEGA X delineated the conservation and evolution of Lablab purpureus PHYA3 (LprPHYA3) probably from PHYA genes of Vigna unguiculata, Glycine max and Vigna angularis. A conserved basic helix-loop-helix motif bHLH69 was predicted having DNA binding property. Domain analysis of GmPHYA protein and predicted partial protein sequence corresponding to exon-1 of LprPHYA3 revealed the presence of conserved domains (GAF and PAS domains) in Lablab purpureus similar to Glycine max. ConclusionPartial characterization of LprPHYA3 would facilitate the identification of complete gene in Lablab purpureus utilizing sequence information from phylogenetically related species of Fabaceae. This would allow screening of allelic variants for LprPHYA3 locus and their role in photoperiod responsive flowering. The present study could aid in modulating photoperiod responsive flowering in Lablab purpureus and other related legumes in near future through genome editing.

EFFECT OF PLANT SPACING, PHOSPHORUS LEVEL, AND TIME OF HARVEST ON FORAGE YIELD OF LABLAB (LABLAB PURPUREUS), CV. HIGHWORTH

A field trial was conducted at Shika, Northern Nigeria to examine the effect of two plant spacings: 30 x 25cm (SI) and 60 x 25cm (S2), four phosphorus leves (75, 100, 125 and 150kgP.ha) and harvesting at 86, 100, 114 and 128 days after planting (DAP) on forage yield of La-blab purpureus cv. Highworth. Closer spacing significantly gave higher (P < 0.05) leaf, stem and total dry matter (DM) yields that wider spacing. Application of phosphorus fertilizer did not significantly (P > 0.p05) influence stem and total DM yield. Leaf DM yield was affected (P < 0.05) by the levels of fertilizer applied. Earlier harvest favoured leaf DM yield, while later harvests gave significantly (P < 0.05) higher stem and total DM yields. The contributions of stem towards the total DM yield increased with age of plant: 86 DAP (55%) < 100 DAP (71%) < 114 DAP (80%) < 128 DAP (89%). The data obtained suggest that a spacing of 30 x 25cm with the application of 100kg P/ha would suffice for satisfactory forage yield.

Yield, Decomposition, Mineralization and Nitrification of Annual Legumes in an Oxisol

Knowledge about seasonal and litter bag soil position effects on litter decomposition (k value), mineralization and nitrification rate of annual legumes in Puerto Rico is limited. This study determined dry matter yield (DMY), k value of litter bags placed below and above the soil surface, mineralization and nitrification rates of Lablab purpureus cv. “Rongai” and Mucuna pruriens (Velvet bean) seeded in the wet and dry season in Oxisol soils (Typic Eustrustox). There was an interaction (p < 0.05) for season and legumes on DMY, k value and N content. “Rongai” DMY was higher for the dry than wet season while Velvet bean had an opposite seasonal response. Higher k value occurred in the wet season for legumes, but “Rongai” had higher k than Velvet bean. For both legumes, N content was higher on litter bag placed below-ground in both seasons. However, in the wet season, there was less N in the above ground litter position. Higher inorganic N was observed at 90 days of soil incubation (DOI) suggesting that N was not available prior to 42 DOI. Nitrification rate was higher for “Rongai” at 22 DOI and lower at 42 and 90 DOI for both legumes. Both legumes enhanced inorganic N, but, regardless of season, Rongai supplied nutrients to the soil faster than Velvet bean. “Rongai” because of its higher k value than Velvet bean is recommended for fast growing row or vegetable crops in Puerto Rico.

Forage Yield, Nutrient Composition and Nutritive Quality of Silage Produced from Maize-Lablab Mixture

Trials were conducted at the Teaching and Research farm, UNAAB in 2008 and 2009 to evaluate the effect of undersowing Lablab (Lablab purpureus cv. Rongai)in maize on grain yield, and to evaluate the nutritive quality of the silage in the dry season using calves.A 2ha piece of land was used for the experiment. In both years, maize was undersown with Lablab two weeks after planting (WAP)the maize. At harvest (10WAP), fresh weights and number of cobs, shelling percentage and weight of 1000grains of maize were determined. Silages of sole maize and maize-lablab in ratio 70:30 were made at harvest in plastic bags. After 4months of conservation, twelve cross-bred (White Fulani x N’dama) calves weighing 71-72kg were randomly allocated to three dietary treatments: grazing + sole maize silage, grazing + maize-lablab silage and Unsupplemented grazing as control for 84days. A seven day trial was also conducted to find out the digestibility and utilization of the maize – lablab and sole maize silage fed to cross-bred calves as supplement in the dry season.Undersowing increased grain yield in the subsequent year. Nitrogen retention was higher (P<0.05) in Maize-lablab and lower in natural pasture. Calves supplemented with maize-lablab silage (70:30) had the highest (P < 0.05) metabolic weight gain (50.03g/kgW0.75) while calves without supplementation had the lowest gain (42.76g/kgW0.75). It was concluded that maize- Lablab silage (70:30) could be used as supplements to enhance the growth and survival of calves during the dry season.Keywords: undersowing, maize-lablab, silage, calves, supplementation

Evaluation of forage legumes for introduction into natural pastures of semi‐arid rangelands of Kenya

AbstractTo address the potential of legumes to contribute to improved quality and quantity of natural pastures in the semi‐arid rangelands of Kenya, five legume species were introduced and evaluated in a small‐plot field experiment over three growing seasons. The investigated species were glycine (Neonotonia wightii), siratro (Macroptilium atropurpureum), dolichos (Lablab purpureus cv. Rongai), velvet bean (Mucuna pruriens) and shrubby stylo (Stylosanthes scabra cv. seca). Treatments included two cutting heights (ground level and 15 cm) and two cutting intervals (at 2 and 4 months). The mean dry matter (DM) yields of glycine and siratro were highest when the legumes were harvested at ground level at 2‐month intervals (10·31 and 7·81 t ha−1 year−1 respectively). Mean DM yield of stylo was highest when the legume was harvested at 15 cm after 4 months (3·52 t ha−1 year−1). These three legumes also produced high organic matter through litter fall, which contributed to soil fertility. Evidence from a supporting pot experiment showed effective nodulation and potential for N fixation. These legumes also possessed deep tap roots and withstood heavy defoliation. These three legumes were selected for further integration with grasses in natural pastures. The DM yields of dolichos and velvet bean when harvested at 15 cm after 2 or 4 months were low (2·48 and 1·91 t ha−1 year−1), and these species were considered inappropriate for further investigation.

Decomposition and nitrogen release by green manure legume residues in different soil types

A laboratory incubation experiment was conducted over a 16-week period to determine decomposition and N release by three green manure legume species, Mucuna (Mucuna pruriens), Lablab (Lablab purpureus cv. Rongai) and Sunhemp (Crotalaria juncea), in three soil types from South Africa. The amount of N mineralized from the residues was determined at 2, 4, 8 and 16 weeks from the onset of incubation. Nitrogen release pattern of the three legume residues followed a similar pattern in all the three soils, with sunhemp treated soil having the highest amount of mineral N after 16 weeks of incubation in all the three soils, followed by lablab and then mucuna. The amount of mineral N ranged from 121 to170, 96 to 134 and 92 to 108 mg kg-1 in the sunhemp, lablab and mucuna treated soils, respectively. The cumulative amounts of N from the legume residues mineralized recovered as mineral N in soil after 16 weeks of incubation ranged from 21 - 41% (92 - 121 mg kg-1), 30 - 68% (108 - 170 mg kg-1) and 26 - 60% (93 - 147 mg kg-1) of the initial added N contained in the residues in the soils with 62, 20 and 12% clay contents, respectively. Less than 50% of the initial added N was mineralized in the high clay content soil. Mineralization rate constant, k, was significantly correlated to the residue N content, net mineralized N, C/N ratio and Lignin/N ratio. Results from this study indicated that all the three legumes could contribute significant amounts of N for uptake by plants, with sunhemp tending to release N at a faster rate, followed by lablab and then mucuna. High clay content in soil slowed down N mineralization. Key words: Green manure legumes, incubation, decomposition, N release, soil type.

Validating economic and environmental sustainability of a short-term summer forage legume in dryland wheat cropping systems in south-west Queensland

The present study set out to test the hypothesis through field and simulation studies that the incorporation of short-term summer legumes, particularly annual legume lablab (Lablab purpureus cv. Highworth), in a fallow–wheat cropping system will improve the overall economic and environmental benefits in south-west Queensland. Replicated, large plot experiments were established at five commercial properties by using their machineries, and two smaller plot experiments were established at two intensively researched sites (Roma and St George). A detailed study on various other biennial and perennial summer forage legumes in rotation with wheat and influenced by phosphorus (P) supply (10 and 40 kg P/ha) was also carried out at the two research sites. The other legumes were lucerne (Medicago sativa), butterfly pea (Clitoria ternatea) and burgundy bean (Macroptilium bracteatum). After legumes, spring wheat (Triticum aestivum) was sown into the legume stubble. The annual lablab produced the highest forage yield, whereas germination, establishment and production of other biennial and perennial legumes were poor, particularly in the red soil at St George. At the commercial sites, only lablab–wheat rotations were experimented, with an increased supply of P in subsurface soil (20 kg P/ha). The lablab grown at the commercial sites yielded between 3 and 6 t/ha forage yield over 2–3 month periods, whereas the following wheat crop with no applied fertiliser yielded between 0.5 to 2.5 t/ha. The wheat following lablab yielded 30% less, on average, than the wheat in a fallow plot, and the profitability of wheat following lablab was slightly higher than that of the wheat following fallow because of greater costs associated with fallow management. The profitability of the lablab–wheat phase was determined after accounting for the input costs and additional costs associated with the management of fallow and in-crop herbicide applications for a fallow–wheat system. The economic and environmental benefits of forage lablab and wheat cropping were also assessed through simulations over a long-term climatic pattern by using economic (PreCAPS) and biophysical (Agricultural Production Systems Simulation, APSIM) decision support models. Analysis of the long-term rainfall pattern (70% in summer and 30% in winter) and simulation studies indicated that ~50% time a wheat crop would not be planted or would fail to produce a profitable crop (grain yield less than 1 t/ha) because of less and unreliable rainfall in winter. Whereas forage lablab in summer would produce a profitable crop, with a forage yield of more than 3 t/ha, ~90% times. Only 14 wheat crops (of 26 growing seasons, i.e. 54%) were profitable, compared with 22 forage lablab (of 25 seasons, i.e. 90%). An opportunistic double-cropping of lablab in summer and wheat in winter is also viable and profitable in 50% of the years. Simulation studies also indicated that an opportunistic lablab–wheat cropping can reduce the potential runoff + drainage by more than 40% in the Roma region, leading to improved economic and environmental benefits.

A novel approach to planting grass - legume pastures in the mixed farming zone of southern inland Queensland, Australia

Reliable establishment of pasture systems with a desirable composition of grasses and legumes remains a challenge in the highly variable climates of the northern grain belt of southern inland Queensland. In this paper, an alternative system is proposed whereby legumes and grasses are planted simultaneously in alternative strips. A 4-year study tested the establishment, production, and botanical composition of the tropical legume species Macroptilium bracteatum cvv. Cardaga and Juanita, Lablab purpureus cv. Endurance, and Clitoria ternatea cv. Milgarra sown as pure stands or with grass strips. The grass strips, and a grass-only treatment, both contained a mix of Panicum maximum cv. Petrie, Dichanthium aristatum cv. Floren, and Bothriochloa insculpta cv. Bisset. L. purpureus was relatively unproductive, yielding ~2000 kg/ha dry matter (DM) produced in each of the first 2 years. M. bracteatum produced 2050 and 3300 kg/ha DM in Years 1 and 2, with declining plant populations and DM in subsequent years. C. ternatea produced 960 kg/ha DM in Year 1, 2730 kg/ha DM in Year 2, and continued to persist throughout the trial, albeit at low DM production levels. The grass-only treatment was dominated by the sown grass species, while the legume-based treatments were dominated by a colonising native species, Dichanthium sericeum, in the fourth and final year. Sowing grass strips adjacent to the legume areas proved a successful strategy, with the proportion of sown grasses in the legume strips increasing to >20% of total DM by Year 4. Soil carbon changes did not differ between treatments, but total C in the top 0.15 m increased from 0.99% in Year 1 to 1.13% in Year 4, representing a net gain of 6.5 t/ha in C over 3 years.

Tolerance to aluminum toxicity by tropical leguminous plants used as cover crops

The objectives of this work were to compare Al tolerance among 17 species of tropical leguminous plants and to evaluate the most appropriate plant characteristic and Al concentration in nutrient solution for tolerance assessment. In addition, three soybean cultivars were included for comparison purposes. There was a great difference among the 17 plant materials tested, when compared by relative root elongation and critical Al activity to reduce 50% of root net elongation. Based on these parameters and on the comparison of two tropical maize genotypes differing in Al tolerance, the following classification was established: highly tolerant, for Mucuna nivea, M. deeringiana, M. aterrima Vigna unguiculata cv. BR 17 and Lablab purpureus cv. Rongai; tolerant for Cajanus cajan cv. IAPAR 43, Canavalia brasiliensis, Calopogonium mucunoides, Cajanus cajan cv. Fava larga, and Crotalaria paulina; moderately tolerant for Crotalaria ochroleuca, Canavalia ensiformis, Crotalaria spectabilis, and C. mucronata; and sensitive for Neonotonia wightii, Crotalaria breviflora and C. juncea cv.IAC-KR1. The three soybeans cultivars were classified as moderately tolerant (Biloxi) and tolerant (IAC 13 and IAC 9).

Annual soil improving legumes: agronomic effectiveness, nutrient uptake, nitrogen fixation and water use

Annual soil improving legumes have a role in the management of soil fertility under the low-input management conditions of resource poor farmers. Several species have been identified as promising for the sub-humid tropical areas of eastern Africa having bi-modal rainfall. Most of these can be intercropped with species used for food and/or have alternative uses for food, forage or weed suppression. We compared five annual legumes for fixation of atmospheric nitrogen, soil water uptake, soil P and nitrate recovery, effects on subsequent crops and for phosphorus recovery from Busumbu P rock. Canavalia [ Canavalia ensiformis (L.) DC] produced the most biomass, fixed the most N, was most efficient in extraction of soil nitrate, and supplied the most N to subsequent food crops. Not unexpectedly, it was also most effective in improving soil productivity. Mucuna [ Mucuna pruriens (L.) DC var. utilis] produced less biomass than canavalia but derived a greater proportion of plant N from the atmosphere, while crotalaria [ Crotalaria ochroleuca G. Don.] and lablab [ Lablab purpureus (L.) cv. Rongai] fixed little nitrogen. Lablab and soybean [ Glycine max (L.)] produced the least biomass. All legumes and food crops failed to acquire significant amounts of P from Busumbu soft rock on this moderately acidic soil. The ratios of C:P in the legume biomass were high enough to cause an early net immobilization of P. Profile soil water status was highest under soybean and lowest under canavalia, reflecting differences in biomass production by the legumes and the subsequent maize–bean intercrop. Surface soil water was similar for all species, but differences were evident at depth. All legumes except soybean extracted water below 1.3-m depth.

Legume and opportunity cropping systems in central Queensland. 1. Legume growth, nitrogen fixation, and water use

An experiment, established on a cracking clay (Vertisol) at Emerald, central Queensland, studied the dry matter (DM) production, nitrogen (N) fixation, and water use of several potential ley-legume species over 4 seasons (1994–1997). Four ley legumes (siratro, Macroptilium atropurpureum cv. Siratro; lucerne, Medicago sativa cv. Trifecta; lablab, Lablab purpureus cv. Highworth; and desmanthus, Desmanthus virgatus cv. Marc) were compared with a pulse (mungbean, Vigna radiata cv. Satin), and grain sorghum (Sorghum bicolor) was included as a non-legume control. Overall, the annual legumes lablab (17.5 t/ha) and mungbean (13.4 t/ha) and the perennial siratro (16.2 t/ha) accumulated more DM than the perennials lucerne (9.6 t/ha) and desmanthus (7.1 t/ha). Lucerne produced little DM in its first year, but in later years had similar production to siratro and lablab. Desmanthus produced >4 t/ha of DM in the first year but barely survived during later seasons. Annual legumes grew faster and exhausted soil water more rapidly than the perennials. The perennials were able to extract more water from the soil than the annual legumes and sorghum, but were inefficient at converting small to moderate rainfall events (25–50 mm) into DM production. During the fallow following the growth of lablab and mungbean, nitrate-N in soil increased and was always greater at the time of re-sowing than for the perennial legumes and sorghum. Initially, the 2 annual legumes derived a high proportion (50% to >70%) of their above-ground N from fixation (%Ndfa) but this declined as the experiment progressed to low values (<13%) in the third and fourth years, reflecting increased supply of nitrate from the soil. In contrast, %Ndfa peaked at 72% for siratro and >90% for lucerne, and remained high (25–50%) throughout the experiment. N fixation rates were strongly negatively correlated with soil nitrate. Over the 4 years, siratro fixed 161 kg N/ha, lucerne 120, lablab 119, mungbean 78, and desmanthus 19 based on above-ground biomass. Mungbean had a net negative N balance (–80 kg N/ha) due to N exported in grain.

Legume and opportunity cropping systems in central Queensland. 2. Effect of legumes on following crops

Poor yields and low grain protein in cereal crops resulting from declining soil fertility, especially nitrogen (N), are major threats to the grains industry in central Queensland. The effect of 4 different pasture-ley legumes [siratro (Macroptilium atropurpureum cv. Siratro), lucerne (Medicago sativa cv. Trifecta), lablab (Lablab purpureus cv. Highworth), and desmanthus (Desmanthus virgatus cv. Marc)] on grain yield and quality of sorghum crops was compared with that of a pulse (mungbean; Vigna radiata cv. Satin) or continuous cropping with grain sorghum (Sorghum bicolor). Legume leys consistently resulted in large increases in grain yield (188–272%), N uptake by sorghum (145–345%), and grain protein (0.21–7.0% increase in grain protein) in sorghum test-crops compared with continuous sorghum crops to which no fertiliser N had been added. The positive effect of legumes persisted up to 3 sorghum test-crops after only 1 year of legumes, although by the third year the effect was comparatively small. Mungbean and lablab generally produced the largest benefit in sorghum test-crops in the first year after legumes, whereas desmanthus and lucerne produced the least benefit. Adding fertiliser N (up to 75 kg N/ha) significantly improved grain yields and N uptake of sorghum test-crops in 3 of 4 years. However, responses to fertilisers were less than those resulting from legumes, which was ascribed to increased availability of legume N to sorghum. Legumes progressively increased soil nitrate in all subsequent sorghum test-crops (compared with continuous sorghum crops), rising from 6.8–18.9 kg NO3-N/ha after 1 year of legumes to 24.2–59.6 kg NO3-N/ha after 3 years of legumes. There was little difference between the legumes in their ability to increase soil nitrate, with the exception of desmanthus, which consistently resulted in the lowest amount of soil nitrate for subsequent test-crops and lowest uptake of N by these crops. Plant-available water content (PAWC) at planting of the sorghum test-crop was only significantly (P<0.05) affected by previous species in 1997, when it was lowest in plots previously sown to siratro and lucerne and highest in sorghum and mungbean plots. In both 1996 and 1997, plots sown to sorghum had significantly higher PAWC at anthesis and grain maturity when previous plots were sorghum rather than legumes.

Improved nitrogen supply to cereals in Central Queensland following short legume leys

Summary. The growth and ability of 12 summer-growing annual and perennial legumes to fix nitrogen and the response of a subsequent wheat crop was examined in a field trial on a deep cracking clay soil in the Central Highlands of Queensland. Twelve legumes [Lablab purpureus cv. Highworth, Vigna radiata cv. Satin, Macroptilium atropurpureum cv. Siratro, Medicago sativa cv. Trifecta, Vigna trilobata (CPI 13671), Macroptilium bracteatum (CPI 27404), Glycine latifolia (CQ 3368), Desmanthus virgatus cv. Marc, Desmanthus virgatus cv. Bayamo, Stylosanthes sp. aff scabra (104710), Clitoria ternatea cv. Milgarra, Cajanus cajan cv. Quest)] and grain sorghum (Sorghum bicolor cv. Tulloch) as a non-legume control were established in November 1994 and their growth monitored until March 1995. The legumes averaged greater than 5 t/ha dry matter production and 77 kg N/ha (above-ground only). Dry matter production ranged from less than 2 t/ha for G. latifolia and M. sativa to greater than 9 t/ha for D. virgatus cv. Bayamo and C. cajan. Annual legumes initially had much higher relative growth rates than the perennial legumes but they rapidily exhausted all the plant available water content of the soil thus allowing the well-established perennials to eventually match this production. The proportion of plant nitrogen (above ground) derived from N2 fixation was generally low, reflecting high soil NO3, but varied widely between species ranging from less than 20% for D. virgatus cv. Marc and G. latifolia to over 45% for C. ternatea, S. scabra and V. trilobata. The quantity of nitrogen derived from fixation was correlated with above-ground dry matter and nitrogen content. There was a significant (P<0.05) growth response by wheat following legumes compared with that following sorghum in the increasing order V. radiata = M. atropurpureum = L. purpureus > C. cajan = M. sativa = V. trilobata = M. bracteatum = G. latifolia > S. scabra = D. virgatus = C. ternatea. Previous legume growth had no significant (P>0.05) effect on yield or nitrogen concentration in a second ‘plant-back’ crop (sorghum). It was concluded that a wide range of pasture-ley legumes have the potential to improve cereal crop production in this region.

Author index — volumes 41–44 (1995)

The development of plant water deficits in soybean (Glycine max cvs. Buchanan and Durack), green gram (Vigna radiata cvs. Berken and CES-ID-21), black gram (V. mungo cv. Regur), cowpea (V. unguiculata cv. Red Caloona), lablab bean (Lablab purpureus cv. Highworth) and pigeon pea (Cajanus cajan cvs. Royes and insensitive ICP 7179) were compared using measurements of leaf conductance (g1) and leaf water potential (ψ1) taken around solar noon at weekly intervals from seedling emergence until maturity on irrigated and unirrigated crops grown in a semi-arid tropical environment. In all grain legumes g1 fluctuated over time in a manner unrelated to soil water availability. Rather, g1 was influenced more by the saturation deficit of the air (δe) in all grain legumes except pigeon pea. In green gram, black gram, cowpea, and lablab bean, ψ1 was maintained at relatively high levels throughout the season independent of soil water content. Fluctuations in g1, and the maintenance of high ψ1, over time prevent the use of g1 and ψ1 as parameters to characterize the development of water deficits in these crops.Diurnal trends were also quantified. There was little recovery in g1 or ψ1 later in the afternoon as the photon flux density (PFD) decreased since δe remained at peak values until dusk. Consequently the correlation between g1 and δe observed in all grain legumes except pigeon pea indicates the importance of early morning photosynthesis to total daily assimilation under both irrigated and unirrigated conditions, although the relative effect of δe on g1 decreased as the availability of soil water declined.The extent of osmotic adjustment was assessed at two stages of growth. Osmotic adjustment was least in black gram and cowpea and greatest in soybean. This information together with trends in g1 and ψ1 were used to examine the physiological responses of different grain legumes to environmental water deficits.

Root nitrogen transformation and mineral composition in selected forage legumes

SummaryA study was conducted at Debre Zeit, Ethiopia to examine the differences in mineral composition, root N contents and their rates of transformation in the soil of different species of four genera of forage legumes,Trifolium steudneri(ILCA D/Z),Trifolium steudneri(Shola),Vicia dasycarpa(ILCA 6795),Vicia benghalensis, Lablab purpureuscv. Rongai,Lablab purpureuscv. Highworth,Medicago scutellatacv. Snail andMedicago truncatulacv. Barrel.M. truncatulacv. Barrel had higher N and P values thanM. scutellatain both roots and tops. Root N contents of the legumes ranged from 2·43% forViciato 0·87% forLablab. These differences were also reflected in the rates of organic root N transformation in soil as determined in laboratory incubation studies.The P concentration in the tops of the legumes ranged from 0·32% inViciato 0·14% inMedicagospp. The observed P concentration in theMedicagospecies suggests a low internal P requirement. Potassium concentrations in theTrifoliumspecies were much higher than the average for all legumes.The results suggest that theViciaspecies used in this study could contribute a considerable amount of N to subsequent crops even when the tops are not returned to the soil. Also, theMedicagospecies are more likely to thrive better under low soil P conditions than the other legumes.

Canopy development in grain legumes grown under different soil water regimes in a semi-arid tropical environment

Differences in the proportion of radiation intercepted at solar noon ( F), leaf canopy development and leaf conductance ( g 1) of soybean ( Glycine max cvs. Buchanan and Durack), green gram ( Vigna radiata cvs. Berken and CES-ID-21), black gram ( Vigna mungo cv. Regur), cowpea ( Vigna unguiculata cv. Red Caloona), lablab bean ( Lablab purpureus cv. Highworth) and pigeon pea ( Cajanus cajan cvs. Royes and insensitive ICP 7179) grown under different soil water regimes were analysed. When water deficits developed immediately following seedling establishment and were unrelieved to maturity the reduction in F was attributed to reduced leaf area development and more vertical leaf orientation, but no leaf loss occurred until near maturity. These reductions in F occurred in all grain legumes before any decreases in g 1 measured at solar noon were observed. In contrast, when water deficits developed from 6 weeks after sowing after an appreciable canopy had developed, F decreased immediately primarily due to leaf loss but did not fall as low as the maximum value of F in the regime where irrigation was terminated at seedling establishment. This indicates that leaf loss is not as sensitive to water deficits as leaf area development. Also, there were immediate reductions in g 1 as well as F when irrigation was terminated 6 weeks after sowing. There were differences among grain legumes in the degree of reduction in F in response to water deficits. Since the measurement of F is simpler and more rapid than the measurement of g 1, and since F is a much more sensitive indicator of the time of onset of water deficits, it is suggested that F be used as an index to quantify the development of water deficits in these crops.

An analysis of the effects of water deficits on grain legumes grown in a semi-arid tropical environment in terms of radiation interception and its efficiency of use

Differences in growth of soybean ( Glycine max cvs. Buchanan and Durack), green gram ( Vigna radiata cvs. Berken and CES-ID-21), black gram ( V. mungo cv. Regur), cowpea ( V. unguiculata cv. Red Caloona), lablab bean ( Lablab purpureus cv. Highworth) and pigeon pea ( Cajanus cajan cvs. Royes and insensitive ICP 7179) in response to water deficits were analysed in terms of the amount of photosynthetically active radiation intercepted ( I) and its efficiency of use in the production of above-ground dry matter ( E c). When water deficits developed slowly from seedling establishment and were unrelieved to maturity, reductions in I were more important than those in E c until at least 42 days after sowing. Thereafter reductions in E c were of greater significance than reductions in I. Integrated over the whole life cycle, the relative reductions in I tended to be greater than the reductions in E c although some grain legumes showed similar reductions in I and E c. In contrast, when water deficits developed rapidly when irrigation was terminated 6 weeks after sowing, the relative reductions in I were generally smaller than the reductions in E c. Over the whole crop cycle, differences in E c between grain legumes varied according to the phenology of the crop and the severity of water shortage. Whilst green gram, black gram, cowpea and lablab been attained the highest E c under well-watered conditions, only the early-maturing green gram and cowpea had the highest E c when water deficits developed immediately after seedling establishment. Differences in the overall efficiency of conversion of incident photosynthetically active wave radiation into combustible energy ( E i), which integrates the effects of water shortage on both canopy development and E c, were not necessarily related to phenology. Lablab bean matured late yet had an E i similar to the early-maturing green gram, and greater than that in soybean, black gram and pigeon pea. Values of E c and E i are compared with published data for different species and water regimes, and the implications for crop productivity in semi-arid tropical environments are discussed.

Stomatal behaviour in grain legumes grown under different soil water regimes in a semi-arid tropical environment

The development of plant water deficits in soybean ( Glycine max cvs. Buchanan and Durack), green gram ( Vigna radiata cvs. Berken and CES-ID-21), black gram ( V. mungo cv. Regur), cowpea ( V. unguiculata cv. Red Caloona), lablab bean ( Lablab purpureus cv. Highworth) and pigeon pea ( Cajanus cajan cvs. Royes and insensitive ICP 7179) were compared using measurements of leaf conductance ( g 1) and leaf water potential ( ψ 1) taken around solar noon at weekly intervals from seedling emergence until maturity on irrigated and unirrigated crops grown in a semi-arid tropical environment. In all grain legumes g 1 fluctuated over time in a manner unrelated to soil water availability. Rather, g 1 was influenced more by the saturation deficit of the air ( δ e ) in all grain legumes except pigeon pea. In green gram, black gram, cowpea, and lablab bean, ψ 1 was maintained at relatively high levels throughout the season independent of soil water content. Fluctuations in g 1, and the maintenance of high ψ 1, over time prevent the use of g 1 and ψ 1 as parameters to characterize the development of water deficits in these crops. Diurnal trends were also quantified. There was little recovery in g 1 or ψ 1 later in the afternoon as the photon flux density (PFD) decreased since δ e remained at peak values until dusk. Consequently the correlation between g 1 and δ e observed in all grain legumes except pigeon pea indicates the importance of early morning photosynthesis to total daily assimilation under both irrigated and unirrigated conditions, although the relative effect of δ e on g 1 decreased as the availability of soil water declined. The extent of osmotic adjustment was assessed at two stages of growth. Osmotic adjustment was least in black gram and cowpea and greatest in soybean. This information together with trends in g 1 and ψ 1 were used to examine the physiological responses of different grain legumes to environmental water deficits.

Phenology, seed yield and water use of grain legumes grown under different soil water regimes in a semi-arid tropical environment

The comparative responses of phenology, and seed yield and its components to prolonged water deficits in soybean ( Glycine max cvs. Buchanan and Durack), green gram ( Vigna radiata cvs. Berken and CES-ID 21), black gram ( V. mungo cv. Regur), cowpea ( V. unguiculata cv. Red Caloona), labaab bean ( Lablab purpureus cv. Highworth) and pigeon pea ( Cajanus cajan cvs. Royes and insensitive ICP7179) was examined during the dry season in semi-arid tropical Australia. In general, water deficits had little effect on the date of flowering, but the duration of flowering and pod-filling was reduced and the time to maturity was markedly shortened. Under well-watered conditions, seed yields were similar in green gram, cowpea, soybean and pigeon pea, with slightly higher yields being obtained in black gram and lablab bean. In contrast, green gram, cowpea and lablab bean produced the highest yield under conditions of water deficit. Early-maturing cultivars yielded better than late-maturing cultivars but inter-species variation in seed yield was not necessarily related to phenology. Most of the reduction in yield arose from a decrease in pod numbers although there was some variation in seed size and seeds per pod. In contrast to absolute yield levels, the reduction in yield due to water deficits relative to the well-watered situation was, with the exception of black graam, greater the later the maturity of the grain legume. Thus the relative reduction in yield was least in green gram, followed by cowpea, soybean cv. Buchanan, insensitive pigeon pea, and lablab bean, with black gram, soybean cv. Durack and pigeon pea cv. Royes having the greatest yield reduction due to water deficits. Variation in productivity was also examined in terms of evapotranspiration (ET) and water use efficiency (WUE DM on a net above-ground dry matter basis, and WUE y on a seed yield basis). Under prolonged water deficits, lablab bean, soybean cv. Durack and both pigeon-pea cultivars extracted the most water. These differences in ET were examined in terms of rooting characteristics. WUE DM was unaffected by water deficits in both soybean cultivars, both green grams and cowpea, but tended to decrease in response to water deficits in the remaining grain legumes. WUE y was more responsive to water deficits than WUE DM. Only in the early-maturing green grams and cowpea was WUE y unaffected by water deficits.

The feed intake and grazing behaviour of cattle grazing a crop of Lablab purpureus cv. Rongai

SUMMARYEating behaviour and the diet selected by cattle progressively defoliating a crop of Lablab purpureus cv. Rongai were measured in three periods each of 12 days. Crop composition during defoliation was recorded.At the beginning of grazing the crop contained 2230 kg green leaf/ha but after 12 days' grazing the crop contained only 300 kg/ha. In the first 6 days cattle selected a diet which contained 85% green leaf but after 12 days' grazing the selected diet contained only 17% green leaf. As available leaf declined, grazing time increased from 465 min on day 1 to 685 on day 6 before declining to 490 min on day 12. Maximum grazing time occurred with a green leaf yield of 1185 kg/ha. The number of eating bites increased from 26000 to 44500 between days 1 and 6 and then declined to 30000 after 12 days' grazing. Grazing time and the number of eating bites were significantly correlated (r = 0·99).Bite size declined from 410 mg organic matter (OM)/bite on day 1 to 90 mg OM/bite on day 12. This decrease in bite size caused a linear decline (927 g/day) in estimated organic-matter intake. The rapid decline in bite size and intake was caused by the reduction in the quantity of leaf per unit area and the lack of desire of cattle to eat stem.It was concluded that the desire of cattle to select leaf is so strong that stem yield should be largely disregarded when considering Rongai as a grazing crop.