In a storage experiment with dairy cow manure, the effects of dietary protein content and manure type on ammonia, nitrous oxide and methane volatilization as well as overall nitrogen (N) loss from manure were investigated. Early-lactating cows received rations with 175, 150 and 125 g crude protein/kg dry matter. Each ration was tested in four manure storage systems reflecting typical farm conditions. These either contained total excreta with high amounts of straw (deep litter manure) or no straw (slurry) or, proportionately, 0.9 of urine and 0.1 of faeces (urine-rich slurry) complemented by the residuals with a low amount of straw (farmyard manure). Manure samples were stored for 7 weeks under controlled conditions and trace gas emission was repeatedly measured. Reduction of N intake decreased daily N excretion and urine N proportion and, on average, led to 0.7-fold lower storage ammonia emission rates on average. Total storage N loss was simultaneously reduced with the extent depending on urine N proportion of the respective manures. A lower dietary protein content furthermore reduced nitrous oxide emission rates in most manure types but increased methane emission from urine-rich slurry; however, global warming potential (based on trace gas output) of all manures was similar with low and high dietary protein content. In deep litter manure, characterized by the highest C: N ratio, emission rates of total N, ammonia and methane were lowest, whereas nitrous oxide values were intermediate. Substantial emission of nitrous oxide occurred with farmyard manure which also had the highest methane values and, consequently, by far the highest global warming potential. C: N ratio of manure was shown to be suitable to predict total N loss from manure during storage in all manure types whereas urine N proportion and manure pH were only of use with liquid manures.
Rumen biohydrogenation of dietary polyunsaturated fatty acids (PUFA) is a significant limitation on any attempt to manipulate the PUFA content of ruminant products (meat or milk). This study examined rumen biohydrogenation of PUFA, the effects of PUFA on other aspects of rumen metabolism and fatty acid flow to and digestion in the small intestine of steers fed on different sources of lipid. Animals were fed ad libitum on grass silage and one of four concentrates (60:40 forage:concentrate on a dry matter basis) containing differing sources of lipid: megalac (rich in C16:0; M), linseed (rich in C18:3n-3; L), fish oil (rich in C20:5n-3 and C22:6n-3; FO) and a mixture of linseed/fish oil (LFO). Diets were formulated so that total dietary oil intake was approximately 60 g/kg of the DM intake, approximately half of which was from the experimental test oil. Rumen NH3-N (P = 0.09) and total VFA concentrations (P = 0.007) were higher on L. FO and LFO compared to M. Dry matter intakes did not differ across treatments and averaged 7.2 kg/day. Intake and flow of fatty acids to the duodenum was 323, 438, 344 and 381 (S.E.M. 9 1; P < 0.001) and 432, 489, 412 and 465 (S.E.M. 18.5; P < 0.1)g/day for M, L, FO and LFO, respectively. Biohydrogenation of C18: 1n-9 was lower than all the other unsaturated fatty acids and it was lower of FO and LFO compared to M and L, on average 66.1 and 72.2%, respectively. Biohydrogenation of C18:2n-6 averaged 89.8% across treatments and was lower (P < 0.05) on M compared to L and FO. Biohydrogenation of C18:3n-3 averaged 92.1% across treatments and was lowest on M (88.8 %) and highest on L and LFO (94.3%). Biohydrogenation of C20:5n-3 and C22:6n-3 averaged approximately 91 and 89 % across the treatments, respectively. Small intestinal digestibilities of all fatty acids were high. In conclusion, feeding different sources of lipid with different fatty acid composition had significant effects on rumen function. The PUFA in whole linseed were only partially protected from biohydrogenation by the seed coat and in contrast to previous reports the C,, PUFA in fish oil were biohydrogenated to a large extent.
Experiments were conducted over the period 1987-94 at Cambridge University Farm and two other sites to examine the effect of various husbandry factors, particularly variety and irrigation regime, on rate, depth and density of rooting in potatoes, Maximum rooting depth ranged from 59 to 140 cm, indicating that potatoes can root to considerable depths and thereby have access to large volumes of water to satisfy the potential demand for water created by,the atmospheric conditions and the size of the canopy. Root extension vertically through the soil profile was best described as a three-phase process: an initial rapid period lasting 3-5 weeks with growth rates c. 1.2 cm/day, a second period of slower growth (c. 0.8 cm/day), followed by cessation of root extension for the rest of the life of the crop. Variety had a major influence on the ultimate depth of rooting, primarily owing to variations in the length of the different periods of rooting rather than the rate in each period. It was observed that changes in the rate, or the cessation of root penetration were always preceded 4-9 days earlier by a change in the rate, or cessation, of leaf appearance. This feature should make it possible to characterize the duration of rooting of varieties through measurement of leaf emergence. Varieties which ceased leaf production early, such as Atlantic, were found to have a duration of root growth of c. 60 days, with Cara rooting for c. 30 days longer. Maximal total root length (TRL) and root length density (RLD) in the experiments reported were 16.9 km/m(2) and 5.5 cm/cm(3), respectively, similar to those found previously in potatoes and crops such as sugar beet, but considerably greater than many other vegetables. Rooting density decreased with depth, but the root systems were not as surface-oriented as many other studies have shown. When TRL was close to its maximum, the vertical distribution of RLD showed that between 40 and 73% was confined to the upper 30 cm, with irrigated crops possessing a greater proportion of their roots in the plough layer. Despite being planted in rows 70-91 cm apart, rooting systems were homogeneously distributed in a horizontal direction by c. 35 days after emergence, at which time the roots had reached a depth of c. 50 cm. Therefore, apart from a short period after emergence, the potato crop is capable of accessing considerable volumes of soil from which to extract water and nutrients. Ensuring that soil conditions are conducive to maximal rates of root growth should be the target for growers, since this will lead to a more efficient use of soil water and irrigation.
Experiments in three dry seasons (1993/94, 1994/95, 1995/96) on a loamy medium sand at ADAS Gleadthorpe, Nottinghamshire, England tested responses of green area, radiation interception, water uptake and above-ground dry matter growth of six wheat cultivars to irrigation. Cultivars differing in date of introduction (Haven 1987, Maris Huntsman 1969, Mercia 1983, Rialto 1991, Riband 1985 and Soissons 1989) were chosen for contrast in flowering time and maximum green area. Maximum soil moisture deficit (SMD) exceeded 140 mm in all years, with large deficits (> 75 mm) from early June in 1994 and more prolonged large deficits in 1995 and 1996, Restricted water availability first affected canopy expansion at a SMD of 74 mm (50 % available water capacity; AW), and canopy senescence at 95 mm (64% AW). Decreases in biomass at harvest were larger with prolonged droughts in 1995 and 1996 (424-562 g/m(2)) than in 1994 (222 g/m(2)). Compared in the two driest years, 1995 and 1996, the decrease in biomass was greater in Haven (599 g/m(2)) than in Maris Huntsman (420 g/m(2)) (P < 0.05). The better drought resistance of Maris Huntsman appeared to arise through its greater water use efficiency (WUE); 6.2 cf. 5.5-5.7 g/m(2)/mm. The susceptibility of Haven to drought was possibly due to restricted water uptake, depression of radiation use efficiency (RUE) and accelerated senescence. The cultivars differed in flowering by up to 9 days but date of flowering correlated poorly with biomass response to irrigation. Early flowering was, however, correlated with favourable distribution of seasonal water use with respect to the grain filling period. The maximum green area index (GAI) of cultivars varied from 4.4 to 5.3 (P < 0.01), but differences were countered by shifts in the extinction coefficient (K), such that season-long radiation interception varied little. Green area index maxima did not therefore relate to the pattern of growth or water use, and they were correlated poorly with the biomass responses. Cultivars did not differ in their maximum depth of water extraction; they all extracted water to 1.65 m depth in each year. It is concluded that early flowering and high WUE might offer scope for improving drought resistance in the UK's temperate climate, but that small maximum GAI seems less useful.
Intensive dairy farming with low N use efficiencies may have adverse environmental impact through nitrate leaching. The residual effects of six different temporary grasslands (1994-96) on yield and nitrate leaching in the following cereal crops (1997-99) were investigated on a loamy sand in central Jutland. The grasslands were unfertilized grass-clover and fertilized ryegrass subject to cutting or continuous grazing by dairy cows with two levels of N in feed supplements. In the first year there was sufficient residual effect of the grazed grasslands to obviate the need for supplementary fertilizer, but in the following years gradually more fertilizer N was required to obtain optimal yields. Nitrate leaching decreased as a function of time after cultivation of grassland, but grassland management had little effect on the subsequent nitrate leaching (6 to 36 kg N/ha in unfertilized plots). Application of cattle slurry to cereals influenced nitrate leaching more than the history of the grassland and caused the annual mean nitrate concentration to exceed the EU Drinking Water Directive upper limit in most cases. Presumably, large differences in N-input during the grassland phase of the crop rotation had relatively little effect on the subsequent N release because of variable N losses during grazing. Possibilities for further improvement of the utilization of grassland N following cultivation are limited when the current knowledge has been implemented. If the N use efficiency of dairy farming systems is to be further improved the utilization of N during the pasture phase is crucial.
Water status traits have been proposed as criteria for drought tolerance improvement in several species especially in bread wheat, oat and barley. In order to test this possibility in durum wheat, in 1995 and 1997, a collection of 144 genotypes from different geographical origins was cultivated under rainfed Mediterranean conditions in Montpellier (southern France). Relative water content (RWC), osmotic potential (OP), as well as leaf morphological traits, grain yield (GY), total above-ground biomass and harvest index (HI) were measured. Large genotypic variations were observed for all traits. Differences between the 2 years were also noticed for all the traits which could be attributed to differences in water availability between the 2 growing seasons. The correlation analysis has revealed significant positive associations between water status traits and both GY and HI within and across years. These results suggest that genotypes which can maintain higher water status and then higher transpiration rates during grain filling, are more efficient in dry matter partitioning to grain and hence higher yield. Heritabilities of water status characters were higher than those of productivity traits. Our results emphasized the value of RWC and OP as criteria for durum wheat grain yield improvement under rainfed Mediterranean conditions. Relationships between RWC, OP and flag leaf morphological traits are also discussed.
It has been previously shown in this laboratory that feeding a model condensed tannin, quebracho tannin, reduces the small intestinal nematode burden in sheep and rats. The aim of the current programme was to determine whether this occurs through direct toxicity against the parasites. Both in vivo and in vitro studies were conducted. The first study compared the effect of dietary quebracho tannin (40 g/kg) on the establishment of the parasitic nematodes Nippostrongylus brasiliensis and Trichinella spiralis in the rat small intestine. The burden of N. brasiliensis, which, although closely associated with the mucosa, actually dwells within the small intestinal lumen, was significantly reduced (P 0.05) by the dietary inclusion of quebracho tannin. The second study involved monitoring the survival of adult N. brasiliensis and T. spiralis when incubated in vitro in varying concentrations of quebracho tannin in Hanks' balanced salt solution. The survival of N. brasiliensis was compromised at concentrations as low as 0.01% (w/v) quebracho tannin but improved with the addition of 0.1% (w/v) polyethylene glycol, which binds to, and inactivates, tannin. T. spiralis was similarly affected, but much more rapidly. These results suggest that dietary quebracho tannin may reduce nematode worm burdens through a toxic effect that requires direct contact between parasite and tannin. This raises the possibility that feeding locally available plant material containing condensed tannins may be an alternative method for controlling parasite infections, especially in areas such as the tropics and subtropics.
Tetraploidy or the use of diploid genotypes with gents conferring high water-soluble carbohydrate concentrations are two mechanisms to increase the nutritive value of perennial ryegrass. This experiment compared the morphology, nutritive value and diurnal variation in water-soluble carbohydrate (WSC) concentrations of 56-day-old plants from six perennial ryegrass cultivars grown under controlled environment conditions. Three of these cultivars were diploid (Melle, Aurora and Cariad) and three were tetraploids (Meltra, Prospero and AberOnyx) which had been derived from the respective diploid cultivars, Two of the diploid cultivars (Cariad and Aurora) had previously been selected for high concentrations of water-soluble carbohydrates. The tetraploid cultivars had fewer (mean 59), larger tillers than the diploids (mean 83). However, with the exception of Melle and Meltra the dry matter yield of the diploid cultivars was not significantly different from their tetraploid derivatives. The effect of tetraploidy on WSC concentrations was dependent on the genetic background of the cultivars. Melle, which had not been previously selected for increased WSC, had a significantly lower WSC concentration than its tetraploid derivative, Meltra. However, tetraploidy did not further increase the WSC concentration in those cultivars previously selected for high WSC concentrations. WSC concentrations in the leaf of both Aurora and Melle rose by 65-70 g/kg throughout the photoperiod, suggesting that differences in the total WSC concentration of these cultivars were not due to any increase in the amount of carbon fixed by Aurora but rather due to differences in the allocation of carbon during growth and development. This experiment demonstrated that tetraploidy was not beneficial in improving the WSC concentration of perennial ryegrass when imposed on two diploid cultivars which had the genetic potential for increased WSC accumulation. However, tetraploidy significantly increased the WSC concentration and by implication the nutritive value of a cultivar derived from a perennial ryegrass cultivar with standard WSC concentrations.
Four extra-short-duration (ESD) lines in 1991 and eight ESD lines in 1992 were grown with adequate soil moisture throughout their growth or subjected to drought coinciding with the vegetative, flowering and god-filling stages under rainout shelters. In both years, drought stress treatments significantly reduced dry matter accumulation and grain yield. The extent of reduction in grain yield varied with the line and stage of stress imposition. Drought stress at the flowering stage caused greater reduction in total dry matter and grain yield than the stress imposed during the pre-flowering and pod-filling stages. Drought stress coinciding with the flowering stage reduced grain yield by 40-55% in 1991 and 15-40% in 1992 in different lines. ESD genotypes could extract moisture from up to a metre depth during pre-flowering and flowering stage stress but less so during the pod-filling stage stress. Genotype ICPL 88039, followed by ICPL 89021, showed consistently lowest sensitivity to drought stress at flowering. Protracted drought stress commencing from the pre-flowering to flowering or from the flowering to pod-filling stages was more harmful than stress at the individual stages. The reduction in yield under drought stress could be attributed mainly to less total dry matter accumulation, but also increased abscission of plant parts. The results suggest variation in sensitivity of ESD lines in relation to timing of stress, which should facilitate targeted screening for different intermittent moisture stress environments.
Understanding the role of pollinators in determining the outcrossing rate is very important for the development of synthetic varieties of faba bean. Isozyme markers have been used to study the multilocus outcrossing rate in five cultivars under field conditions and in two locations. The study was carried out at Cordoba (Spain) and at Rennes (France). These two locations were chosen because previously studies showed strong differences in cross-pollination. Multilocus outcrossing rates at both locations, Cordoba and Rennes, were 0.65 and 0.33 respectively. Local differences in pollinator abundance and foraging activity were 26 and 32 times higher, respectively, at Cordoba than at Rennes which could explain an outcrossing rate twice at Cordoba compared with Rennes. So, pollinators may play a prominent role in determining the differences in outcrossing between locations. However, at a local level, there is a highly significant positive correlation between foraging activity and outcrossing only at Rennes (where the number of pollinators is scarce) but not at Cordoba (where pollinators are abundant). We suggest that although pollinators have a major impact on the level of outcrossing, in circumstances where there are a Lot of pollinators the differences in outcrossing between cultivars depends on other factors among which is the ability of the genotype itself to outcross. No type of floral display seems to be clearly important in the determination of the outcrossing level in such a case. The implication of our results for faba bean breeding strategies is discussed.
Forty-eight high genetic merit Holstein/Friesian dairy cows with Predicted Transmitting Abilities for milk fat plus protein yield, calculated using 1995 as the base year (PTA(95) fat plus protein), of 40.0 kg, were used in an eight treatment, two period (period length = 8 weeks) change-over design experiment Diets were offered ad libitum in the form of a complete diet. Treatments comprised a high and medium feed value silage, with concentrates being incorporated into the diet at proportional inclusion rates of 0.10, 0.30, 0.50 and 0.70 of total dry matter with the high feed value silage, and at 0.32, 0.48, 0.64 and 0.80 of total dry matter with the medium feed value silage. The high feed value silage was produced from a primary regrowth herbage (regrowth interval of 33 days) which was wilted prior to ensiling, while the medium feed value silage was produced from a primary growth herbage harvested on 9 June 1995. The high and medium feed value silages had estimated metabolizable energy concentrations of 12.4 and 11.3 MJ/kg DM respectively. Animals commenced treatments after a mean post calving interval of 26 days. Irrespective of silage feed value, total dry matter intake and milk yield tended to increase with increasing proportion of concentrate in the diet. Milk protein concentrations increased to concentrate inputs of 0.50 and 0.64 of total DM with the high and medium feed value silages respectively, but decreased at the highest concentrate inclusion rates. Milk fat concentrations tended to decrease at higher concentrate inclusion rates. The milk yield responses to increasing proportion of concentrate in the diet have been described by a pair of significantly different equations: Y = 34.2 - 11.9 x 0.0101(x) and Y = 34.2-28.5 x 0.0101(x) for the high and medium feed value silages respectively (where Y = milk yield (kg/day) and x = concentrate proportion in the diet on a dry matter basis). Similarly, milk fat and milk protein yields for the two silage types have been described by pairs of significantly different equations. Using these milk yield response equations, it can be calculated that at a concentrate proportion in the diet of 0.32 total dry matter, an additional 3.7 kg of milk per day would be produced by offering the high, rather than the medium feed value silage, while at a concentrate proportion of 0.70 total dry matter, the milk yield benefit associated with the high feed value silage was reduced to 0.6 kg per day. Similarly, total dry matter intakes for animals offered the high feed value silage were 7.4 and 0.8 kg per day greater than for animals offered the medium feed value silage, at concentrate proportions in the diet of 0.32 and 0.70 total dry matter, respectively. These responses indicate that at low concentrate inclusion rates in the diet, silage feed value has a major influence on animal performance, while at higher concentrate inclusion rates, the importance of silage feed value is reduced.
Between 1989 and 1999, 33 experiments tested the effects of potassium (K) fertilizer on the yield and quality of potatoes. The experiments were done on a range of soil types and used varieties and management conditions common to modern commercial production. The average yield in these experiments was 48 t/ha. Nearly half of the experiments were done on soils that had exchangeable K values 170-210 kg K/ha. When applied at the optimal rate, the effects of K fertilizer on tuber dry matter concentration were nonsignificant. Exceeding the optimal K application rate caused occasional reductions in tuber dry matter concentrations particularly if potassium chloride (KCl) was used. In the two experiments where it was tested, application rate and form of K had no effect on crisp fry-colour. The effect of K fertilizer on tuber K concentration was measured in 21 experiments and on average each tonne of fresh weight yield was associated with 4.2 kg K, The range in values was large, 2.8-5.7 and related to soil exchangeable K. For fertilizer recommendations based solely on the probability of a significant yield response to K fertilizer it is suggested that no more than 210 kg K/ha he applied even on soils with < 120 mg exchangeable K/1. For fertilizer recommendations based on crop K removal, an uptake value of 4.8 kg K/t fresh weight (FW), as has been suggested, would be adequate, although errors in the estimation of yield may lead to over or under application of K. Since there was little evidence to support fertilizer policies that apply more K than is removed by the crop a fertilizer recommendation system based primarily on the probability of a yield response would be more than sufficient.
Low organic matter concentration coupled with low native soil phosphorus (P) concentrations is a major constraint limiting the productivity of a soybean-wheat system on Vertisols in the Indian semi-arid tropics. In a 3-year field study (1996-99), the performance of four different composts obtained from legume straw (Glycine max Merr.L), cereal straw (Triticum aestivum), oilseed straw (Brassica juncea L.) and city rubbish were compared, and also with chemical fertilizers in terms of degree of maturity, quality of compost, improvement in soil organic matter, biological activities of soil and yields of soybean and wheat. Phospho-sulpho-nitrocomposts (phosphocomposts) were prepared containing approximately 2.5 to 4.2% P and 1.4 to 2.3% N, in an aerobic decomposition process for 4 months by adding an aqueous slurry of 1:1 (dry weight) cow dung, 2.2% P in the form of low grade Mussorie phosphate rock (7.5% P), 10% pyrite (S, 22.2%) and 0.5% urea N, and bioinoculums such as the cellulose decomposers Paecilomyces fusisporus and Aspergillus awamori, and P-solubilizing organisms i.e. Bacillus polymyxa and Pseudomonas striata. The maturity indexes were strongly associated with the source of materials, chemical composition and degree of decomposition, The matured composts had lower C/N ratios (8.2 to 21.7) and water soluble carbohydrates (0.23 to 0.43%) and larger ratios of cation exchange capacity/total organic carbon (CEC/TOC) and lignin/cellulose than the initial. The matured compost increased total P, water soluble P, citrate soluble P, total N and NO3-N and the application of phosphocompost at the rate of 10 t/ha gave plant growth dry matter accumulation, seed yield and P uptake by soybean equivalent to single superphosphate at 26.2 kg P/ha. The continuous turnover of enriched phosphocompost increased soil microbial biomass C and the activity of enzymes compared to application of chemical fertilizer.
A study was conducted on a 15 x 15 diallel set of tomato excluding reciprocals to find out the extent of heterosis, combining ability and nature of gene action for yield with two important quality traits: ascorbic acid (vitamin C) and total soluble solids (TSS). Significant differences among genotypes were obtained for all three traits. Positive high significant heterosis was found for yield (41.97, 157.84 and 28.94%), for ascorbic acid (16.68, 54.57 and 161.33%) and for TSS (25.97, 11.93 and 19.02) over the top, the better parent and the commercial control respectively. The magnitude of variance due to general as well as specific combining ability were highly significant indicating the importance of both additive and non-additive gene action. However degree of dominance (o(-2) g/o(-2) s) revealed the prevalence of a non-additive gene effect. Cross combinations Arka Vikas x Sel-12 (13.19), KS-10 x Pant T-3 (1.66) and EC 8 18703 x EC 13042 (0.88) were best specific combiners for ascorbic acid, total soluble solids and yield/plant. Predominance of non-additive gene action plays a greater role in the inheritance of ascorbic acid and total soluble solids in tomato under hill conditions.
A rotation experiment was conducted on an alluvial soil at Central Potato Research Station, Jalandhar, India between 1994 and 1999 to develop an integrated nutrient management programme for a potato-sunflower-paddy rice rotation. It tested 10 fertilizer treatments that combined application of 50, 100 and 150% of the recommended rates of inorganic nitrogen (N), phosphorus (P) and potassium (K) with farmyard manure (FYM) and in some cases zinc. Potatoes were the most nutrient-responsive crop followed by paddy rice and sunflower. The responses of potatoes to both P and K were greater in frost and late blight years. In these experiments potatoes required NPK at 150% of the currently recommended rate for maximum tuber production (i.e. they required 270 kg N, 52 kg P and 150 kg K/ha). Application of FYM at 30 t/ha with 270 kg of inorganic N/ha (FYM + N) was less effective than the use of NPK at 150% of the currently recommended rate. Application of K to replace that removed in the harvested crop was more effective in potatoes than giving K at 100 or 150% of the currently recommended rate. Sunflowers grown after potatoes that had received NPK at 150% of the currently recommended rate or with the FYM + N treatment required only half of the currently recommended rate of NPK for maximum yield (i.e. they required 23 kg N, 7 kg P and 13 kg K/ha), whereas paddy rice, grown as a third crop, required the full amount of NPK at the currently recommended rate (i.e. 120 kg N, 26 kg P and 67 kg K/ha). Application of K to adjust for its removal did not benefit sunflowers or paddy rice. Zinc had no direct effect on potatoes or any residual effects on the succeeding sunflower and paddy rice crops. The effects of the FYM + N treatment were cumulative, especially on potatoes which were the most responsive crop, whereas those involving the application of NPK at 150% of the currently recommended rate were not. Also, the NPK fertility of the soil was enhanced and more organic carbon was present following the FYM + N treatment than with NPK fertilizers applied at the currently recommended rate. Application of P resulted in a build-up of P but none of the treatments, even the applications of K to adjust for its removal, maintained the K status of the soil at its initial level.
Experiments at three sites in 1993. six sites in 1993 and eight sites in 1995, mostly after oilseed rape, tested effects of previous fertilizer N (differing by 200 kg/ha for 1993 and 1994 and 300 kg/ha for 1995) and date of sowing (differing by about 2 months) on soil mineral N and N uptake by winter wheat cv. Mercia which received no fertilizer N. Soil mineral N to 90 cm plus crop N ('soil N supply'; SNS) in February was 103 and 76 kg/ha after large and small amounts of previous fertilizer N respectively but was not affected by date of sowing. Previous fertilizer N seldom affected crop N in spring because sowing was too late for N capture during autumn, but it did affect soil mineral N, particularly in the 60 90 cm soil horizon. presumably due to over-winter leaching. Tillering generally occurred in spring, and was delayed but not diminished by later sowing. Previous fertilizer N increased shoot survival more than it increased shoot production. Final shoot number was affected by previous fertilizer N, but not by date of sowing. Overall, there were 29 surviving tillers/g SNS. N uptakes at Fortnightly intervals from spring to harvest at two core sites were described well by linear rates. The difference between sowings in the fitted date with 10 kg/ha crop N was 1 month. these dates were not significantly affected by previous fertilizer. N uptake rates were increased by both previous fertilizer N and late sowing. Rates of N uptake related closely to soil mineral N in February such that 'equivalent recovery' was achieved in late May or early June. At one site there was evidence that most of the residue from previous fertilizer N had moved below 90 cm by February, but N uptake was nevertheless increased. Two further 'satellite' sites behaved similarly. Thus at 14 out of 17 sites. N uptake until harvest related directly and with approximate parity to soil mineral N in February (R-2 = 0.79). a significant intercept bring in keeping with an atmospheric contribution of 20-40 kg/ha N at all sites. It is concluded that, on retentive soils in the UK, SNS in early spring was a good indicator of N availability throughout growth of unfertilized wheat. because the N residues arising from previous fertilizer mineralized before analysis, yet remained largely within root range. The steady rates of soil mineral N recovery were taken as being dependent on progressively deeper root development. Thus, even if soil mineral N equated with a crop's N requirement, fresh fertilizer applications might be needed before 'equivalent recovery' of soil N, to encourage the earlier processes of tiller production and canopy expansion. The later process of grain filling was sustained by continued N uptake (mean 41 kg/ha) coming apparently from N leached to the subsoil(relating to previous fertilizer use) as well as from sources not related to previous fertilizer use. significant net mineralization was apparent in some subsoils.
The aim of this study was to select the best arrangements of MP-PCR (micro sa tellite-primed PCR) for routine large-scale fingerprinting of flax cultivars. We found optimum PCR conditions for the application of five previously published primers (PCT1-PCT5) to flax cultivar fingerprinting. We modified to optimum MP-PCR which was targeted to flax tetrameric [GATA] microsatellite loci specified by primer PCT6. We found that after a reamplification PCR step was involved we were able to generate highly discriminating fingerprinting patterns, which distinguished all eight flax cultivars individually. In particular primers 3PCT1 and 3PCT2 were promising for future large-scale fingerprinting due to the production of most polymorphic bands. Increasing annealing temperature within a temperature profile helped to generate new polymorphisms within flax microsatellite patterns especially with primer 3PCT2. Using this primer we succeeded in generating new polymorphic bands after increasing annealing temperature from 55 degreesC to 60 degreesC, and to 65 degreesC. A cluster analysis of flax cultivars was performed based on microsatellite data, The core group of eight flax cultivars was clustered into two homogeneous subclusters. A lower level of cultivar clustering within subclusters was not detected.
The effect of water stress, commencing from the late cell division period, on in vivo grain growth was studied in relation to grain sucrose, water status and in vitro starch synthesis. Detached ear experiments were conducted to assess the effect of sink dehydration on grain filling processes under non-limiting source conditions. Water stress caused premature grain desiccation and resulted in a marked decline in grain sucrose and reduced grain weight. Both sucrose uptake and conversion to starch in vitro were increased by mild water stress (solute potential (Psi (s))-0.8 MPa). However, a decline in Psi (s) below this optimum resulted in reduced sucrose uptake and starch synthesis not attributable to a reduced supply of sucrose. Stressed grains which failed to accumulate dry matter in vivo showed significant starch synthesis when cultured in vitro. Grains from in situ and osmotically stressed plants showed a lower capacity for starch synthesis in vitro. The results indicate that grain filling processes under stress conditions are limited by (1) low substrate availability and low Psi (s) within the sink i.e. an unfavourable seed environment (non-lasting effect) and (2) reduced synthetic capacity of the sink (carry-over effect).
A joint model for plot yield in response to fertility trends and interplot competition is described. The model combines the mixed model representation of a cubic smoothing spline to model fertility and a regression model with auto-regressive terms to model competition. Estimation is based on a generalization of residual maximum likelihood. The methods were applied to a series of 70 sugar beet trials conducted by the Plant Breeding Institute, Cambridge, UK, and the results summarized.
CERES-Rice model was used to simulate growth and yield of four common rice varieties in Thailand with the attention on rate and timing of N application, a factor that most limits crop yield. The model predicted slightly higher grain yield than that observed for all varieties at N input of 75 kg/ha, but the differences between observed and simulated yields were not significant, except for varieties HSP and SPR90. The simulated grain: straw ratio was significantly higher than the observed value for all varieties except that of HSP. There was no significant difference between the simulated and observed values of days to flowering. Generally, the model reasonably predicted the phenology and yields of RD23 and KDML105 varieties. The model was also used to compare the yields of KDML105 variety as influenced by rate and timing of N application grown in acid sulphate soils. There was a variation in predicted biomass yield with applied N rates at 0 and 150 kg/ha, but timing of application had no effect. In Aerie Endoquept and Sulfic Tropaquept soils at Suphan Buri and Pathum Thani rice research stations, the yield patterns remained unchanged and showed a positive response to N rate up to 75 kg/ha. The model estimated higher grain yields beyond 75 kg N/ha while the observed yield decreased. Based on the simulated yields for a 10-year period at the Asian Institute of Technology (AIT), Pathum Thani, Suphan Buri, Nakhon Pathom and Ratcha Buri rice research stations the varieties were ranked as: SPR90 > RD23 = HSP > KDML105., The model suggested that SPR90 is the most suitable variety for the central plain and its potential yield ranges from 4030 to 5600 kg/ha. Pathum Thani province, with acid sulphate soils, had the lowest potential for rice production.