The present study investigated how increasing silica content modifies the chemical and morphological characteristics and microbial degradation of rice straw. Two rice straws grown on culture media with different silica contents were collected and analysed for chemical and morphological composition and ultrastructure. Silica content (g/kg DM) of the two straws was high (98.0, straw H) and low (0.0, not detected, straw L). The ground (2 mm) straws were incubated in the rumen of three ruminally cannulated cows for 4, 8, 16, 24, 48 and 96 h for in sacco degradability measurements. The main fractions (stem, leaf sheath and blade) of each straw were incubated for 24 It. Kinetics were fitted to an exponential model with lag time. Scanning electron microscopy was used to examine intact fragments of stems and fragments incubated for 6, 24, 72 and 96 h in cow rumen. X-ray analysis was carried out on non-incubated fragments for silica mapping. A reduction of stem content from 320 to 270 g/kg straw, and an increase in leaf sheath content from 360 to 400 g/kg straw, were found for an increase in silica content from 0 to 100 g/kg DM. Chemical composition differed little between straws H and L, except for ash and silica contents. The ash originated mainly from the leaves and increased with silica content from 70 to 140 g/kg DM. The DM degradability was lower in the H than in the L straw. This reduction came mainly from a lower non-NDF component degradation in straw H. Stems were more degraded than leaf fractions for DM, NDF and non-NDF components; their degradation was depressed in the H straw. X-ray analysis showed that the deposition of silica on the stem epidermis was different, with a thick layer on H stems and no deposition on L stem surfaces. As a consequence, microbial colonization and degradation were faster on the epidermis of straw L. Epidermal silica did not hinder degradation from the internal cavity.
The field experiments were carried out at the Indian Agricultural Research Institute, New Delhi during 1996-97 to 1998-99 to study the effect of phosphate solubilizing bacteria (PSB) and incorporation of wheat and rice residue on the relative efficiency of diammonium phosphate (DAP) and Mussoorie rock phosphate (MRP) in three cycles of rice-wheat cropping system. Application of MRP had no significant effect on grain and straw yield and P uptake by rice and wheat; however, when it was inoculated with PSB, it increased grain and straw yields as well as P uptake of both rice and wheat. Efficiency of MRP+PSB was further increased when rice and wheat residues were incorporated and this practice made MRP on a par with DAP. Available P in soil after three cycles of rice-wheat cropping was more after MRP+PSB and incorporation of rice and wheat residues than after DAP. The results of the present study, therefore, indicate that low grade rock phosphate such as MRP can be advantageously utilized in rice-wheat cropping system when applied with PSB inoculation and incorporation of rice and wheat residues.
Parental, F-1, F-2, BC1, BC2, BC11, BC12, BC21, BC22, BC1 self-pollinated and BC2 self-pollinated generations of three crosses involving six cultivars of durum wheat (Triticum turgidum var. durum) were studied for flag leaf length under normal and late sown environments to analyse the nature of gene effects. For most crosses the 10-parameter model was the best descriptor of the data to account for the variability in generation means of this trait but in cross HI 8062xJNK-4W-128 the 6-parameter model was the best (normal sown) while in cross Raj 911 x DWL 5002 the 3-parameter model was the best (late sown). Of the epistatic interactions, dominance x dominance (l) and dominance x dominance x dominance (z) played significantly greater roles in controlling the inheritance of this trait. Absolute totals of non-fixable gene effects were much higher than the fixable gene effects in all the crosses in both the environments, indicating the greater roles of non-additive effects in controlling the inheritance of flag leaf length in durum wheat cultivars. Significant partial dominance was observed frequently in most of the crosses. Significant heterosis was attributed to combined effects of dominance x dominance (l), additive x additive x dominance (x) and dominance x dominance x dominance (z) epistatic interactions in the cross Cocorit 71 x A-9-30-l under late sown environment. Biparental mating and/or diallel selective mating, which exploit both fixable and non-fixable components, have been suggested for the improvement of this trait in durum wheat cultivars.
Differences in development among wheat cultivars are not only restricted to photoperiod and vernalization responses. When both requirements are fully satisfied differences may still arise due to earliness per se. It is not clear at present to what extent this trait is 'intrinsically' expressed (a constitutive trait) independently of the environmental conditions so that it might be selected under any thermal condition or if it may be altered to the extent of showing a crossover interaction with temperature in which the ranking of wheat genotypes may be altered. The present study assessed the influence of temperature on the intrinsic earliness for lines of diploid wheat characterized for their differences in a major gene for intrinsic earliness, but also possibly differing in their genetic background for other factors controlling this polygenic trait. To do so the lines were grown individually in two temperature regimes (16 and 23 degreesC) under long days having previously been fully vernalized. Multiple comparisons analyses were carried out among lines of the same allelic group for the EpsA(m)1 gene. Results indicated that within each group there were lines that did not differ in their earliness per se, others differed but without exhibiting any line x temperature interaction and finally different types of interaction were shown, including cases where the ranking of lines was altered depending on the growing temperature. It is thus possible that the selection of a genotype based on its earliness per se in an environment might not represent the same performance in another location where temperature varied significantly.
The composition of animal manure is influenced by the diet fed. Efforts arc made to decrease nitrogen emission from pig production by optimizing diet composition. This normally results in a lower proportion of N excreted in urine relative to faeces, and may also influence the turnover and utilization of manure N after field application. The effects of pig feed composition on the excretion of urinary and faecal N, on the dynamics of manure N in soil and on the potential utilization of manure N in the field was Studied. Growing pigs and sows were fed 12 different diets with variable contents of fibre and protein (with or without synthetic amino acids). Slurries consisting of a mixture of faeces and urine were stored according to common agricultural practice in Northern Europe. The plant availability of N in the resultant slurries originating from animals fed known diets was tested in small field plots with barley, under conditions with minimal N losses. Separate plots were fertilized with increasing amounts of mineral N. Nitrogen uptake in barley was determined and the utilization of slurry N was compared with that of mineral fertilizer N. The net release of mineral N and C from the slurries in soil was also measured in a parallel incubation Study. The mineral fertilizer equivalent of pig slurry N was 72-100 % and significantly influenced by feed fibre composition, but not significantly influenced by the protein content. There was a significant positive correlation between enzyme-digestible organic matter in the pig diet (measurement used for feed evaluation) and the plant availability of pig slurry N (R-2=0.90). The ammonium content of stored pig slurry could not be used for prediction of the N availability since the net mineralization of pig slurry N was variable, but there was a significant negative correlation between the pig slurry C/N ratio and the plant availability of slurry N (R-2=0.86). Increased dietary concentration of fermentable structural carbohydrates (e.g. by including sugar beet pulp in the diet) reduces the excretion of N in urine without affecting the availability of slurry total N, whereas an increased concentration of dietary fibre with a low fermentability (straw) results in less urinary N, but also a lower plant availability of slurry N.
The effects of nitrogen (N) rate and timing on need for fungicide application in winter wheat (Triticum aestivum) were investigated in 3 years of field experiments on loamy sand soils in Denmark. A two-factor completely randomized experimental design was used, comprising seven combinations of different N fertilizer rates and application times, and five doses of fungicide (co-formulation propiconazole and fenpropimorph). Two different varieties of winter wheat with high susceptibility, to powdery mildew (Blumeria graminis) were used, Florida in the first season and Pepital in the last two seasons. The severity of powdery mildew and septoria leaf spot (mainly Septoria tritici) varied between seasons from slight to moderate with powdery mildew dominating in the first season and septoria leaf spot in the last season. The severity of both powdery mildew and septoria leaf spot assessed as the Area Under the Disease Progress Curve (AUDPC) was increased by application of N in all years, and more so by early applied N. Grain yields increased with increasing N rate and fungicide dose. However, the observed grain yields did not reveal any N x fungicide interactions. Regression models were therefore fitted, relating grain yield to rate and timing of N fertilizer and to AUDPC of powdery mildew and septoria leaf spot, and relating AUDPC to rate and timing of N fertilizer and to fungicide dose. They demonstrated that septoria leaf spot had a considerably higher impact on grain yield than mildew. The optimal fungicide dose and N rate were defined as those giving the highest economic return. The regression models were used to estimate the effect of N rate and timing on optimal fungicide dose, and the effect of fungicide application on optimal N rate. The optimal fungicide dose increased almost linearly with N rate above a minimum N rate, but with a large dependency on price relations. Early applied N caused a higher demand for disease control. The fungicide applications in the model were mainly driven by the need to control septoria leaf spot, whereas powdery mildew gave a poor net return for control. The estimated optimal N fertilizer rate for untreated diseased crops was 60 kg N/ha lower than for crops without disease. The use of fungicides with an efficacy twice that of the EBI-fungicides used in this experiment would increase the optimal N rate by c. 20 kg N/ha.
Eighteen S-1 lines of maize (Zea mays L.) derived from a low nitrogen tolerant pool and two inbred lines were evaluated for agronomic performance under moderate N conditions in the southern Guinea savannah of Nigeria. Generally, the breeding lines differed in yield, growth, vertical root-pulling resistance, N-uptake and N-use efficiency. Breeding lines with high vertical root-pulling resistance took up more N and utilized it more efficiently. They also showed better agronomic performance and recorded higher yields. Principal component and cluster analyses classified the breeding lines into six groups. The results of principal components analyses (PCA) suggest that the most important variables for the classification of the S-1 lines were grain yield, plant height, total dry matter during the grain-filling period and at maturity, N-accumulation, N-uptake and N-use efficiency. Other important traits were days to silking, anthesis-silking interval, ears per plant, harvest index and vertical root-pulling resistance. Two groups containing a total of 14 S-1 lines that had higher agronomic performance than others are recommended for further evaluation under severe N stress to ascertain their tolerance of low N stress before recombination to form a new population for the next cycle of selection.
Perennial ryegrass (Lolium perenne L.) is often subject to transient waterlogging during winter under dryland conditions and summer when flood-irrigated. Despite this, little is known about the physiological responses of perennial ryegrass genotypes to waterlogging. In a pot experiment, four perennial ryegrass genotypes with contrasting root growth characteristics were subjected to waterlogging for 0, 3, 7, 14, 21 or 28 days. The masses of roots and shoots of the genotype Aurora6 were not significantly (P>0.05) reduced by waterlogging, throughout the experiment. All other genotypes exhibited reductions in root and shoot biomass between 14 and 21 days after waterlogging was imposed. The masses of laminae and roots of susceptible genotypes were reduced by up to 70% after 28 days of waterlogging. Aurora6 was also able to maintain photosynthesis for longer into the waterlogging period. However, after 28 days of waterlogging, photosynthesis of all genotypes was reduced by 30-50%. The waterlogging tolerance of Aurora6 was not due to its relatively poor root growth, as its progeny (2178), which also had poor root growth under control conditions, was susceptible to waterlogging. These findings show that there is variation in physiological processes and herbage yield of perennial ryegrass under waterlogged conditions. The implications of these findings for the genetic improvement of waterlogging tolerance of perennial ryegrass are discussed.
Faecal indices were evaluated to assess organic matter digestibility (OMD) for small ruminants fed with Digitaria decumbens. A continuous digestibility trial was conducted with five Creole bucks and five Black-belly rams, fed with fresh cut Digitaria decumbens from 15 to 70 days of re- growth. The amount of herbage offered, the refusals and the faeces were weighed daily for each animal during 55 days. Herbage and faeces samples were kept to determine dry and organic matter (DM and OM), crude protein (CP), neutral and acid detergent fibre (NDF and ADF) and lignin contents (ADL). OMD was calculated per week and per animal. Predictive regressions of OMD were calculated for each species, from all the faecal components measured (CPf, NDFf, ADFf and ADLf), using linear or curvilinear models. Regressions from CPf had the lowest residual standard error (<0.028) when calculated for each species, compared with regressions from the other faecal components. Among the regressions from CPf, the lowest standard error of the predictive parameters was obtained with a model in the form of a-b/CPf, for each species. The latter allows prediction of OMD at pasture, consistent with theoretical energy requirement for both goats and ewes grazing a Digitaria decumbens based sward.
Data from a two-factorial experiment carried out during 3 years were used to analyse the effects of crop nitrogen (N) status on disease development, and the effects of N supply and disease on light interception (IPAR) and radiation use efficiency (RUE) in winter wheat (Triticum aestivum). The factors in the experiment comprised seven strategies of N fertilizer application including different N rates and timing of application, and five doses of fungicide application for control of the leaf diseases powdery mildew (Blumeria graminis) and septoria leaf spot (Septoria tritici). Light interception was estimated from weekly measurements of crop spectral reflectance. The increase of crop dry matter was mainly affected by N fertilizer and disease through effects on IPAR. Early N application increased IPAR and thus dry matter growth more than later N application. A split N strategy may ensure both high N uptake and high growth rates of the crop. Only septoria leaf spot significantly reduced RUE. Septoria leaf spot was found to be up to nine times more detrimental to grain yield than powdery mildew for similar severity levels. Fungicide applications may therefore be reduced in cases of low powdery mildew severity combined with low crop susceptibility to this disease. This low susceptibility was found to be obtainable with split N application strategies, as the severity of both powdery mildew and septoria leaf spot increased with increasing leaf N concentration. A similar but smaller correlation was obtained between disease severity and canopy size. Measurements of canopy size using spectral reflectance may be used as a simple indicator of general crop susceptibility to disease, whereas measurements of leaf N concentration may be used as input into decision support systems for fungicide application.
Data from several field experiments (eight crops grown under a widely varying nitrogen supply on a loess loam soil) were used for a simulation modelling based analysis of nitrogen availability of cauliflower. The model was built out of components describing root growth, nitrate transport to the roots and the vertical nitrate transport within the soil. Root observations obtained over 2 years indicated an increased fraction of dry matter allocated to the fine roots under N deficiency. An adapted version of a root growth model for cauliflower described the rooting data with an R-2=0(.)75. Based upon an acceptable description of the soil water budget, vertical nitrate movement during the growth period of cauliflower was accurately described. The magnitude of this movement, however, was limited to soil depths of about 60 cm even after periods of high rainfall, because of a high soil water holding capacity. An analysis of the factors determining nitrate availability indicated that apparent mass flow was only of high importance for conditions of extremely high N supply where high amounts of nitrate nitrogen remain in the soil up to the end of the growing season. Otherwise, the dominating fraction of nitrate has to be transported to the roots by diffusion. Single root model based calculations of maximum nitrate transport to roots overestimated N availability as indicated by estimates of critical soil nitrate N that were too low. The introduction of a restricted uptake activity period of the roots was used to bridge the gap between theoretical calculations and empirical results. Scenario calculations were carried out to obtain functional relationships between N supply and residual soil nitrate levels for different soil conditions and management practices.
Associations of characters were studied in linseed using data of 60 accessions evaluated in a randomized complete block design with three replications under glasshouse and field conditions during 2000 and 2001. The main objectives were to determine the magnitude of correlations between yield and its components under variable environments, and identify stable and major yield attributes that could support further improvements of linseed productivity. The degree of character association varied considerably across years and locations, due mainly to climatic factors (e.g. temperature, moisture levels, etc.) and disease incidences. However, seed yield per plot was significantly (P<0.01) and positively associated with seed yield per plant, 1000 seed weight and bolls per plant across environments. These three yield attributes were also strongly and positively correlated with plant height. branches per plant, days to flowering and maturity. Oil yield was significantly and positively associated with polyunsaturated (linoleic and linolenic) fatty acids, whereas it was negatively correlated with saturated (palmitic and stearic) fatty acids. Oil yield also had a weak positive relation with monounsaturated oleic acid. The quality of linseed oil, which is dependent on the levels of these fatty acids, can be influenced by the correlated responses of these variables in reaction to different environmental factors. Thus, knowledge on the causes and effects of these correlated responses arc necessary to undertake Sound and effective selection programmes.
Greater white clover (Trifolium repens L.) competitive ability can increase the forage quantity and quality of clover-grass mixed stand (MS) cropping. The present work assessed the relationship of clover competitive ability with morphophysiological traits, and the efficiency of direct and indirect selection procedures for increasing clover dry matter (DM) yield in MS. Some 165 large-leaved clover genotypes representative of Italian Ladino germplasm and 13 clover genotypes from an elite small leaved population were clonally evaluated for one year in pure stand (PS) and in MS environment with Italian ryegrass (Lolium multiflorum Lam.) and tall fescue (Festuca arundinacea Schreb.) that reproduced the level of interspecific interference met by the clover over a multi-year crop cycle. Results for all genotypes and their Subsets indicated that the level of leaf size variation among tested genotypes can affect the results. Wider variation decreased the relative importance of clover genotype x evaluation environment interaction, because competitive ability was mainly correlated with traits (longer petiole; larger leaflet) contributing to scale foraging in MS and yielding ability in PS. Competitive ability tended to be more closely associated with other traits (high stolon density; plasticity of petiole elongation) contributing to foraging ability, i.e. the ability to make fine-scale exploitation of light and nutrients in MS, within germplasm of similar leaf size. Leaf size variation also affected the relative efficiency of selection procedures estimated from expected responses to clonal selection. Results for all entries indicated direct selection in MS as 23% more efficient than selection in PS based on a selection index including three traits associated with competitive ability (petiole length; stolon density; leaflet size) which, in turn, was predicted to be 16% more effective than selection in PS based on DM yield. The advantage in relative efficiency of direct selection was almost doubled when considering only large-leaved germplasm. In a second experiment, evaluating 16 clover half-sib progenies of elite large-leaved parents for 2 years in PS and in MS with Italian ryegrass, tall fescue and cocksfoot (Dactylis glomerata L.), direct selection was estimated to be over three-fold and 68% more effective than indirect selection in PS based on DM yield and the selection index, respectively, based on expected responses to genotypic selection. The selection index may improve the efficiency of preliminary, PS-based clonal selection. Further evaluation of elite genotypes and/or their polycross progenies in MS is recommended for final selection.
The present study was conducted from 1998 to 2000. to evaluate seasonal water use and soil-water extraction by Kabuli chickpea (Cicer arietinum L.). The response of three cultivars to eight irrigation treatments in 1998/99 and four irrigation treatments in 1999/2000 at different growth stages was studied on a Wakanui silt loam soil in Canterbury. New Zealand. Evapotranspiration was measured with a neutron moisture meter and water use efficiency (WUE) was examined at crop maturity. Water use was about 426 min for the fully irrigated treatment and at least 175 ruin for the non-irrigated plants. There was a significant correlation (P<0.001) between water use and biomass yield (R-2=0.80) and water use and seed yield (R-2=0.75). There were also highly significant (P<0.001) interacting effects of irrigation, sowing date and cultivar on WUE and the trend was similar to that for seed yield. The estimated WUE ranged from 22-29 kg DM/ha per rain and 10-13 kg seed yield/ha per lam water use. The three chickpea cultivars were capable of drawing water from depths greater than 60 cm. However. Most of the water use (0.49-0.93 min/10 cm soil layer per day) came from the top 0-30 cm, where most of the active roots were concentrated. The study has shown that using actual evapotranspiration and water-use efficiency, the biomass yield and seed yield of Kabuli chickpeas can be accurately predicted in Canterbury. Soil water shortage has been identified as a major constraint to increasing chickpea production. Drought was quantified using the concept of maximum potential soil moisture deficit (Dp(max)) calculated from climate data. Drought responses of yield, phenology, radiation use efficiency and yield components were determined, and were highly correlated with Dp(max). The maximum potential soil moisture deficit increased from about 62 min (irrigated throughout) to about 358 min (dryland plots). Chickpea yield, intercepted radiation and the number of pods per plant decreased linearly as the Dp(max) increased. Penman's irrigation model accurately described the response of yield to drought. The limiting deficit for this type of soil was c. 165 and 84 mm for the November and December sowings in 1998/99 and 170 min in 1999/2000. Beyond these limiting deficits. yield declined linearly with maximum potential soil moisture deficits of up to 358 nun. There was little evidence to support the idea of a moisture sensitive period in these Kabuli chickpea cultivars. Yield was increased by irrigating at any stage of crop development, provided that the water was needed as determined by the potential soil moisture deficit and sowing early in the season.
The canopy development, radiation absorption and its utilization for biomass production in response to irrigation at different growth stages of three Kabuli chickpea (Cicer arietinum L.) cultivars was studied on a Wakanui silt loath soil in Canterbury, New Zealand (43degrees38S, 172degrees30E). The study also aimed at quantifying the yield potential of the crop under varying irrigation regimes and sowing dates. Green area duration (GAD), intercepted radiation (F-i), radiation use efficiency (U) and total intercepted PAR were significantly (P4.7 t/ha), and there was no indication of a critical period of sensitivity to water stress. Based on results collected in the first growing season a simple model relating seed yield to radiation interception, U and HI was made. Results froth the second growing season were then used as a simple verification to test the accuracy of predictions. The results suggest that these varieties have the potential to yield more than 4.5 t/ha of seed in Canterbury.
The physical parameters of oats of prime importance in determining milling quality are kernel content. the content of free kernels, hullability and screenings. In addition to screenings, hectolitre weight is used in the commercial trading of grain as an indicator of quality due to the absence of suitable methods. for commercial use, for determining the parameters that are closely related to milling quality. The effects of nitrogen (0-200 kg/ha), seed rate (200 and 300 seeds/m(2)) and plant growth regulator, chlormequat chloride, on grain quality were investigated at two locations, in one spring and three autumn sown experiments, in 1997/98 and 1998/99. Yields increase(] at higher rates of nitrogen and at the higher seed rate but were not significantly affected by chlormequat chloride. The effects of nitrogen rate and seed rate on kernel content were inconsistent but overall there was a small reduction at the higher nitrogen and higher seed rates and where chlormequat chloride was applied. In general, free kernels were reduced at the higher rates of nitrogen, at the higher seed rate and where chlormequat chloride was applied. Hullability improved at higher rates of nitrogen but was poorer at the higher seed rate and with chlormequat chloride. Screenings increased and hectolitre weight declined at the higher rates of nitrogen, the higher seed rate and with chlormequat chloride. The decline in hectolitre weight due to treatments within each experiment in general was associated with reductions in kernel content, content of free kernels and an increase in screenings. However, variation in hectolitre weight did not reflect variation in kernel content, free kernels and screenings between experiments. Overall, the changes in quality due to nitrogen rate, seed rate and chlormequat chloride were small compared with differences between varieties.
The content of starch and the activities of enzymes involved in starch biosynthesis were examined in developing grains of field grown rice (Oryza sativa L.) plants. Enzyme activities were monitored throughout the grain filling period of cultivar Tainting 67 and its NaN3-induced Mutant SA419. The activities of most of the grain enzymes involved in starch biosynthesis increased and reached their maxima during the initial period of grain development, then gradually declined towards the later stages of grain filling. Both Tainting 67 and SA419 showed different starch and amylose accumulation patterns in different grain positions. In cultivar Tainting 67, reduced activities of grain enzymes involved in starch biosynthesis, particularly during the early phase of grain filling, were related to the decreased starch accumulation for the grains located oil proximal secondary branches as compared with the Brains located oil distal primary branches. The decreased amylose contents in the grains of Tainung 67 located oil proximal secondary branches were attributable to their lower granule bound starch synthase and starch debranching enzyme activities at early and mid phases of grain filling. In Mutant SA419. no significant changes were observed in the activities of grain enzymes involved in sucrose to starch conversion between the grains located oil distal primary and proximal secondary branches of the panicle. As a result, grain setting position was found to have little effect oil the contents of starch and amylose for these developing grains located oil different branches. Thus, the Mutant SA419 did have some agronomic and physiological traits that were superior to its wild type cultivar Tainung 67.
Field experiments were undertaken during 1998-2000 at Askov Experimental Station and Lundgard Experimental Site, Denmark, to investigate the fertilizer value of anaerobic and aerobic sewage sludges (SS1 and SS2), composted household waste (Compost) and farmyard manure (FYM). The organic residues were applied at two rates with or without supplementary mineral nitrogen (N). The effects of residue application on spring cereal dry matter (DM) yield and N-offtake were related to reference treatments with increasing rates of calcium ammonium nitrate (CAN). DM yields at the high application rates of aerobic sewage sludge (198 kg N/ha/year) and farmyard manure (300 kg N/ha/year) were comparable to the reference treatments receiving 90 kg mineral-N/ha/year. The comparable high application rate of anaerobic sewage sludge was 138 kg N/ha/year only and the DM yield was less. In contrast, the yield effect of Compost was very poor; even the high application rate of 321 kg N/ha/year yielded less than the low application rates of aerobic sewage sludge and farmyard manure, 66 and 100 kg N/ha/year, respectively. The nitrogen fertilizer replacement value (NFRV) of the organic residues was estimated for all four combinations of the response variables DM-yield and N-offtake and the independent variables of total-N and ammonium-N applied. NFRV was in the range 49-68% for the sewage sludges and FYM based on the DM-yield:total-N relation, and slightly smaller for the N-offtake:total-N relation. 29-53%. The highest values were obtained for the aerobic sewage sludge, having a potential manurial Value comparable to FYM. In contrast, the NFRV of Compost was low, about 10%. The concentration of ammonium-N in organic residues and manures is often used for predicting the fertilizer value. Ammonium-N based NFRV of 160-210% for the sewage sludges indicate that water extractable ammonium-N underestimates the NFRV, probably due to the content of easily degradable organic matter in digested sewage sludge. The estimated NFRV for Compost was above 100% but connected with high uncertainty. In contrast, the ammonium-N based NFRV for FYM was only 70-87%, probably due to ammonia volatilization caused by incomplete incorporation of large quantities and the high ammonium-N:total-N ratio in this residue.
Calliandra calothyrsus is a tree legume native to Mexico and Central America. The species has attracted considerable attention for its capacity to produce both fuelwood and foliage for either green manure or fodder. Its high content of proanthocyanidins (condensed tannins) and associated low digestibility has, however, limited its use as a feed for ruminants, and there is also a widespread perception that wilting the leaves further reduces their nutritive value. Nevertheless, there has been increasing uptake of calliandra as fodder in certain regions, notably the Central Highlands of Kenya. The present study, conducted in Embu, Kenya, investigated effects of provenance, wilting, cutting frequency and seasonal variation both in the laboratory (in vitro digestibility, crude protein, neutral detergent fibre, extractable and bound proanthocyanidins) and in on-station animal production trials with growing lambs and lactating goats. The local Kenyan landrace of calliandra (Embu) and a closely-related Guatemalan provenance (Patulul) were found to be significantly different, and superior, to a provenance from Nicaragua (San Ramon) in most of the laboratory traits measured, as well as in animal production and feed efficiency. Cutting frequency had no important effect on quality; and although all quality traits displayed seasonal variation there was little discernible pattern to this variation. Wilting had a much less negative effect than expected, and for lambs fed calliandra as a supplement to a low quality basal feed (maize stover), wilting was actually found to give higher live-weight gain and feed efficiency. Conversely, with a high quality basal diet (Napier grass) wilting enhanced intake but not live-weight gain, so feed efficiency was greater for fresh material. The difference between fresh and wilted leaves was not great enough to justify the current widespread recommendation that calliandra should always be fed fresh.