Biomass production of Lolio‐Cynosuretum grassland is not increased by plant‐species richness

In experimental grasslands, a positive relationship between biomass production and plant diversity has often been found. Here, we compared a moderately species‐rich old sward with its grass‐dominated counterpart (12 vs. 8 species per 2.5 m², or 8.3 vs. 0.7% yield proportion of dicots at the start of the experiment) established by herbicide application. We hypothesized an increased N, P and K uptake in the diverse sward related to a higher colonization rate with arbuscular mycorrhizal fungi (AMF), the presence of legumes, and complementary nutrient use of plant species. Phosphorus or N fertilizer application (according to contributions of AMF or legumes) were expected to balance the assumed smaller biomass production of the grass compared to the diverse sward. In two experimental years, N, P and K uptake, biomass production, N₂ fixation, and intra‐ and extraradical AMF colonization were investigated in an untreated control and plots that were fertilized with P and N in a low (P1: 20 kg P ha^?1; N1: 50 kg N ha^?1) or a high dose (P2: 100 kg P ha^?1; N2: 500 kg N ha^?1) in both swards. Biomass production was larger in the grass compared to the diverse sward. The N, P and K uptake, accumulated over three harvests (or 1.5 years), was also larger in the grass sward. The biomass production ranged from 5.3 to 10.0 t ha^?1 and accumulated nutrient uptake from 82 to191 kg N ha^?1, 19 to 31 kg P ha^?1 and 112 to 221 kg K ha^?1. Small legume proportions resulted in an accumulated N₂ fixation between 0 and 3 kg ha^?1. In the second year, the root length colonized with AMF structures was larger in the diverse compared to the grass sward, and the root length colonized with arbuscules and coils was larger in the N2 treatment compared to the control in the diverse sward. There were hints to higher AMF abundance under conditions of limited P availability (low soil P content, high N:P ratio in plant biomass). We conclude that in semi‐natural grassland of moderate species richness several factors may affect the relationship between plant diversity and productivity, i.e., management, plant species identity, and the number of the plant species of the low‐diversity level.     

Organic matter returns to soils must be higher under organic compared to conventional farming

The aim of this paper is to discuss the demand of fresh organic matter (FOM) supply to maintain soil organic matter (SOM) levels and productivity of arable soils under organic management. The basic question is whether the different frame conditions in organic vs. conventional farming result in a different and system‐specific FOM demand. If this is the case, it would follow that the farming system has to be considered in the calculation of SOM balances. SOM balances are the most common decision support tools in organic matter management. A conversion to organic farming in practice usually leads to an increase of SOM levels as well as soil microbial activity over time. The system‐specific driver of this effect is the indispensable extension of the share of (perennial) legumes in crop rotations at the expense of non‐legumes such as cereals, row crops, and maize. Extended legume cropping is essential for N supply in crop rotations as the import of N fertilizer in total is limited by organic farming regulations and mineral N fertilizer may not be used at all. Based on this characteristic of organic management, we argue that the demand of FOM supply to soils must be higher than in conventional crop production. The most relevant factors are (1) the non‐existence of mineral N fertilizer as an external N source that supports the maintenance of SOM by decreasing the demand for SOM‐N, (2) benefits of increasing SOM stocks and turnover for soil productivity under organic management, and, (3) increased mass‐losses of FOM and easily degradable SOM compartments due to higher microbial activity in soils. These effects have to be quantified and must be considered in SOM balances in order to avoid misleading assessments and erroneous decisions.     

Amino acid composition,relative nutritive value and in vitro protein digestibility of several Philippine indigenous legumes

This study demonstrates variability in amino acid composition among accessions of several Philippine indigenous legumes. Moreover, two accessions ofD. lablab were identified to have high level of methionine (>2%). Methionine was identified as the first limiting amino acid with leucine, and threonine as the second limiting amino acids for most legumes studies.The IVPDs of the legumes under study ranged from >70 to 79%. Raw mature seeds had relatively low RNVs of 11 to 68% which increased to 68 to 94% and 51 to 89% after boiling and roasting, respectively.     

Yield andin vitro nutritional quality of some leguminous seed protein isolates

Seed protein concentrates (SPC) were extracted from 4 leguminous species and the extractabilities of total N (nitrogen), protein N and SPC determined. In addition, composition, calorie value andin vitro enzymatic digestibility of these SPCs was analysed. Results indicate the promising nutritional potential of these SPCs.     

Improvement of legumes by exploring extra-specific genetic variation

Summary Genetic improvement of legumes is a major on-going challenge for plant breeders. Outlined in this review are the main reasons why such increased extra-specific genetic variation is required, particularly in the developing world. With the development of new methods of plant genetic manipulation it is necessary to assess the relative merits of all approaches now available. To help the plant breeder in this respect we have in this review comprehensively described these conventional and unconventional procedures with particular reference to economically important legumes.supported by the Royal Society Commonwealth Bursary.     

Ecotypic differentiation in Medicago polymorpha L. along an environmental gradient in central Chile. RAPDs studies show little genetic divergence

Burr medic (Medicago polymorpha) is distributed in a wide range of bioclimatic and edaphic conditions throughout the mediterranean-climate region of Chile. Previous studies on populations of M. polymorpha collected along this gradient revealed a remarkable ecotypic differentiation in many adaptive traits. Random amplified polymorphic DNA (RAPD) was used to evaluate genetic divergence in 36 accessions collected along the entire gradient. Three Australian commercial cultivars were also included in the study, of which two originated in Chile. The 40 RAPD primers used revealed a high degree of polymorphism and generated a total of 295bands, of which 78% were polymorphic. Degrees of similarity, based on Nei's genetic distance, identified one group of accessions (22 of the 39studied) with an index of similarity = 100% centered in the semiarid and arid zones of the study region. The remaining 17 accessions (from more mesic zones and one commercial cultivar) were more diverse. Only 91%similarity was found for the combined 39 accessions, indicating a low degree of genetic divergence. Biogeographical and life history strategy aspects of the results are discussed, including the notion of a suite of ‘arid-adapted’ characteristics arising in annual legumes under arid /semiarid conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Morphological characterization of Mediterranean populations of Biserrula pelecinus L.

A collection of 24 populations of Biserrula pelecinus L. (biserrula)from Italy (Sardinia), Spain. France (Corsica). Morocco and Greece was evaluated in nursery rows at Perth, Western Australia. Fifteen morphological traits were recorded and chromosome numbers of representative populations were counted: The quantitative characters were analysed using principal component analysis and k-means clustering. The chromosome number of all accessions was 2n= 2x= 16. In other respects there was substantial variation in biserrula collected from the Mediterranean basin, the Moroccan populations in particular being distinct, some with strongly curved pods and others with long linear pods. All Greek populations had while flowers and large seeds. Populations from Italy. France and Spain were similar, with linear pods, blue flowers and smaller seeds. Most populations from Morocco were early flowering, had larger leaves, longer pods and produced more seeds per plant than other populations. All populations were extremely hard seeded (>98% hard-seeded after a one-summer exposure on the soil surface). It wits concluded that there is sufficient variation in Mediterranean populations of biserrula lo initiate a selection programme for southern Australia, and other areas with Mediterranean-type climates, especially for areas where serradella ((Ornithopus compressus L.) is adapted. Seed production is far easier than for serradella, and this advantage alone offers potential for its use in duplex soils where the deep rooting habit of serradella gives it an ecological advantage over conventional pasture legumes.     

Asymmetric relationship between grasses and forbs: results from a field experiment under nutrient limitation

We compared the role of grasses and forbs in managed grassland under nutrient‐poor conditions via the experimental removal of one of these two species groups and an evaluation of the removal effects over a 5‐year chronosequence (beginning 4 years after removal start), focusing on above‐ground biomass and community composition. There was evidence for the complementarity of grasses and forbs, as shown by better relative performance of both groups in the mixture, measured as the proportional deviation of their above‐ground biomass from that predicted using single‐group plots. Relative performance of forbs was better than that of grasses and did not change significantly throughout the experiment. Relative performance of grasses decreased, reaching a minimum value of 0·03, but then increased to 0·71, in parallel with increasing legume proportion in the above‐ground biomass (from 0·9 to 5·1%). The botanical composition of the grass group did not respond to forb removal. Among the forbs, subordinate species sensitive to light competition became more abundant after removal of grasses; the forb species richness increased on average by 1·6 species per plot. Our results show that the composition and diversity of the forb group is affected by the presence of grasses, and the presence of forbs in a grassland community assures higher temporal stability in above‐ground production. Under increasing depletion of soil nutrients, the grasses derive substantial benefits from the presence of legume species and possibly also from the other forb species. The study supports the need for realistic, long‐term experiments to better understand plant community dynamics.     

Micronutrient concentrations in common and novel forage species and varieties grown on two contrasting soils

We investigated differences between forage species with regard to micronutrients that are essential to sustain livestock health. Five grasses (timothy, perennial ryegrass, meadow fescue, tall fescue and cocksfoot), three legumes (red clover, white clover and birdsfoot trefoil) and four forbs (ribwort plantain, salad burnet, caraway and chicory) were grown on one micronutrient‐poor/low pH soil and one micronutrient‐rich/high pH soil (outdoor pot experiment). In addition, six grasses (timothy, perennial ryegrass, meadow fescue, tall fescue, Festulolium hybrid and cocksfoot) and one legume (red clover) were field‐grown on the micronutrient‐poor soil. Of the twelve pot‐grown species, herbage of chicory, red clover and white clover generally had the highest micronutrient concentrations (maximum Co, Cu, Fe and Zn concentrations were 0·23, 9·8, 233 and 109 mg kg^?1 DM, respectively), except for Mo, which was highest in the clovers (10·6 mg kg^?1 DM), and Mn, which was highest in cocksfoot (375 mg kg^?1 DM). Soil type had the strongest effect on plant Mo and Mn concentrations. We also investigated differences in micronutrients between varieties, but they were generally few and negligible. The results indicate that choice of forage species is of major importance for micronutrient concentrations in herbage and that soil type exerts a major effect through pH. Forage of chicory, red clover and white clover generally met the requirements of high‐yielding dairy cows with regard to most micronutrients; therefore, diversification of seed mixtures so as to include these species could increase micronutrient concentrations in forage.     

Cover Crop Effects Increasing Carbon Storage in a Subtropical No‐Till Sandy Acrisol

The long‐term (8‐year) effects of summer (Mucuna spp.) and winter cover crops (Avena strigosa + Vicia sativa and Lolium multiflorum + Vicia sativa) in maize‐based cropping systems on the total, particulate, and mineral‐associated soil carbon (C) stocks in the 0‐ to 0.2‐m layer of a no‐till South Brazilian Acrisol (87 g kg^?1 clay) were evaluated. Annual C sequestration rates and the carbon management index (CMI) were calculated taking a fallow/maize (F/M) system as reference. A greater average C sequestration rate (0.68 Mg ha^?1 yr^?1) and greater C lability (particulate C/mineral‐associated C) were observed in the soil under the Mucuna system, and this was related to the higher biomass input in comparison to the winter cover crop systems. These cropping system effects on amount and lability of soil C were summarized through the CMI. The results highlight the potential of C retention in soils under warm and humid subtropical climate through the adoption of high C input summer cover crops in no‐till production systems aimed at further improvement in soil and environmental quality.