This is part of the text of an invited lecture given by R. K. Scott on 1 December 1998, the first in a series to commemorate the memory of R. Hull, the first Director of Broom's Barn. Dr Hull devoted his career to the science underpinning the homegrown sugar industry.

The prediction of silage feeding value from the analysis of herbage at ensiling and the effects of rate of nitrogen (N) fertilizer, date of harvest and treatment additive at ensiling on fermentation, dry matter (DM) recovery and effluent production were evaluated in a factorial experiment. Herbage was harvested from 75 plots, laid out in three replicate blocks of 25, from the primary growth of a predominantly perennial ryegrass sward. The plots received 72, 96, 120, 144 or 168 kg N/ha and were harvested on 10, 17, 24 or 31 May or 7 June. Herbage was ensiled for 176 days in laboratory silos (6 kg capacity), either untreated or treated with formic acid or a bacterial inoculant, each applied at 3 ml/kg herbage. Increasing the rate of N fertilizer and delaying harvest date increased herbage DM yield but decreased silage digestible organic matter digestibility (D-value) and intake potential (P < 0·001).

Increasing the rate of N fertilizer increased crude protein (CP), acid insoluble N (AIN) (P < 0·001), acid detergent fibre (ADF) (P < 0·01) and acid detergent lignin (ADL) concentrations but had no statistically significant effect (P > 0·05) on pH or the concentrations of ammonia N, lactic or volatile fatty acids. Delaying harvesting date decreased CP, AIN and ADF concentrations (P < 0·001) and effluent DM losses (P < 0·001). Treatment with either formic acid or inoculant decreased silage pH and the concentrations of ammonia N, acetic acid and propanol and increased AIN, ethanol, neutral detergent fibre (NDF), ADF and cellulose concentrations, effluent volume, DM losses and intake potential. Formic acid treatment decreased D-value (P < 0·001), whereas inoculant treatment was not statistically significant (P > 0·05). For potential silage and metabolizable energy (ME) intakes and D- value, strong positive correlations (P < 0·001) were identified with herbage pH, buffering capacity and concentrations of CP, AIN, true protein nitrogen (TP), while negative correlations (P < 0·001) were identified with herbage yield and concentrations of NDF and hemicellulose. With untreated silages, strong positive correlations (P < 0·001) were identified between silage pH and herbage pH and concentrations of AIN, buffering capacity, ash, TP and negative correlations (P < 0·001) were identified with herbage DM yield and concentrations of DM and WSC. Herbage yield and concentrations of NDF, TP, DM and nitrate N provided the best linear relationship for predicting potential ME intake of the resultant untreated silages (R2 = 0·94). It is concluded that delaying harvest date had the most detrimental effect on silage feeding value, although this effect was partially overcome by reducing the rate of fertilizer N and use of either an inoculant or formic acid additive. Silage feed value was also highly correlated with the protein and fibre fractions, ash, buffering capacity and pH of the herbage at ensiling.

Two separate experiments, in clay loam and loamy sand (prepared by mixing the clay loam with washed sand), were performed to determine the effects of sowing method and sodicity on the survival, ion uptake, grain yield and yield components of spring wheat (Triticum aestivum L.) cv. Kharchia- 65. Three sodicity levels (control, exchangeable sodium percentage (ESP) 5–7; low (ESP 18–20); high (ESP 39–40)) and four sowing methods (sowing dry and pre-germinated seed and transplanting of 16 and 21-day-old seedlings) were tested. In the control and at low sodicity, sowing method had no effect on plant survival, grain and straw dry weight per plant. However at high sodicity, these variables were lower in plants established from pre-germinated seed than in plants established from dry seed, the farmers' normal practice. In contrast, transplanted seedlings showed increased survival and had significantly higher grain and straw dry weight than plants established by sowing dry seed. Differences in grain yield between sowing method and sodicity treatments were mainly due to differences in the number of grains per plant. Although increasing sodicity was associated with higher concentration of Na+, and lower concentrations of K+, Ca2+, Mg2+ and lower K+/Na+ ratio in flag leaf sap, ion concentrations were unaffected by sowing method.

It is suggested that the increased survival and yield of transplanted seedlings is due to the fact that they are not exposed to sodicity during the sensitive stages of germination and emergence. In addition, their already established roots and shoots may be better able to capture the resources required to support their subsequent growth. The decreases in grain and straw dry weight per plant, and the increases in these parameters achieved by transplanting seedlings instead of sowing dry seed, were greater in clay loam than in loamy sand. Further studies are required to determine whether the responses to transplanting observed here also occur in sodic soils under field conditions, and to investigate the technical and economic feasibility of adopting this technique in commercial agriculture.

A field study was conducted to investigate the agronomic performance, nitrogen (N) efficiencies, yield components and yield of rice in Spain for different nitrogen treatments. The experimental variants were six preflood N rates (0, 50, 75, 100, 125 and 150 kg/ha) and three topdressing patterns: (i) non- topdressed, (ii) topdressed with 50 kg N/ha at mid-tillering stage (MT) and (iii) topdressed at panicle initiation stage (PI). The N status of the plant was measured at different growing stages to determine whether a chlorophyll meter would be useful in making N sidedress recommendations. The results showed that grain yield increased with increasing amounts of preflooding N fertilizers up to 100 kg N/ha. The main effect was on panicle number per unit ground area. The effect of additional N supply on yield components and grain yield depended on application timing. Split applications of N did not improve the agronomic efficiency but reduced days to maturity and lodging and increased the harvest index value. Split applications increased grain yield when the total N rate was 150 kg/ha with the second supply at PI. There was a significant but not very good relationship between N content and chlorophyll content (SPAD) values. The regression equation differed significantly depending on growth stage. The SPAD value may determine the need for N topdressing at MT stage, but not at PI. However, the relationship between SPAD value and the rice yield increase from N topdressing application was not very good.

The objective of the study was to determine, in the absence of competition (0·74 plants/m2), the existing variation within lines of maize (Zea mays L.) for plant and ear traits (yield per plant, number of tillers, number of ears, plant height, number of nodes, ear length, and kernel row number), as well as the relationship between hybrid potential yield per plant (i.e. yield per plant in the absence of competition) with line traits. Two categories of material were tested in honeycomb trials, grown from 1989 to 1995 in the University farm of Thessaloniki, Greece. The first category were selections from long-term inbreds B73 and Mo17, derived through honeycomb design in the absence of competition, and their crosses. Inbred selections and their crosses were evaluated in different years. For the second category two sets of S5 lines, A and B, derived through controlled selfing from the commercial single- cross hybrid PR 3183, were used in random crosses between S5 plants of lines A and B and resulted in 40 triplets; each triplet included each of the selfed parent, and their hybrid. Triplets of A and B S6 lines and A × B S5 × S5 crosses were evaluated in the same experiment. Significant differentiation among lines and hybrids was found for almost all traits; variation within lines for potential yield per plant, even in case of B73 and Mo17, seemed to be transmissible to the hybrids. Although correlation values were small in the case of B73 and Mo17 selections, there was a positive correlation between hybrids and lines for their potential yield per plant. Selection for high yield within S lines gave ‘prolific’ plants, with line prolificacy being correlated with hybrid potential yield per plant.

The success of Linum usitatissimum as a commercial crop depends on its value for seed/oil (linseed) and/or fibre/straw production (flax). In the present study we evaluated nine linseed × linseed and two linseed × flax crosses for their potential to produce recombinant inbred lines (RILs) that give higher yields for dual-purpose (high seed–high fibre) traits. Analysis of the early generations indicated that while all crosses segregated for seed weight, straw weight, capsule weight and total plant weight, some crosses lacked the necessary genetic diversity to produce superior RILs. The performance of F3 families supported this conclusion as only two crosses were identified which had adequate potential to produce improved RILs with high seed and straw/fibre yields. The four most heterotic crosses identified in a previous experiment showed little potential for transgressive recombinants, although the best of these RILs would make better dual-purpose varieties compared to existing cultivars. Genotypic correlations were generally positive and should increase the chances of extracting RILs producing both high seed/oil and straw/fibre yields.

Controlled release (CR) formulations can significantly influence the fate of carbofuran in the environment. The influence of three alginate-encapsulated CR formulations compared with the granular formulation (G10%) on the mobility of carbofuran in sandy clay loam soil and sandy loam soil was investigated. In flooded soil the leaching potential of the three alginate controlled release formulations tested was decreased more than nine times (not more than 3%) compared with the G10% (28%). Most of the released carbofuran was confined to the top 0–5 cm of the soil column followed by the second 5–10 cm layer and the least was found in the fourth section (15–20 cm). The data obtained for a sandy loam soil irrigated by drip irrigation showed that the greatest proportion of carbofuran leached through the columns was from the G10% (52%) compared with 3–4% from CR formulations over a 30-day period. The carbofuran concentrations found in different soil depths showed similar trends to those for the flooded soil. Based on the residue levels recorded within the 20 cm depth, the relative retention ratio of carbofuran in sandy clay loam versus sandy loam soil was 1·2[ratio ]1 for the controlled release formulations and 1·9[ratio ]1 for the G10%.

Aqueous extracts of fruits and leaves of the Chinaberry tree, Melia azedarach L. were tested for their efficacy versus other biotic and synthetic insecticides against the pea leafminer, Liriomyza huidobrensis (Blanchard). The study included field experiments on naturally infested swiss chard, Beta vulgaris var. Cicla L., and greenhouse experiments on artificially infested cucumber, Cucumis sativus L. that were conducted in 1995–96. The other treatments included azadirachtin (0·25%), ultrafine mineral oil, abamectin, cyromazine, imidacloprid, pyrazophos and control. Results of field experiments indicated that Melia fruit extract and the other insecticides significantly lowered the number of larvae per swiss chard plant as compared to the control, at 5 days sampling after second spray or 15 days after first spray, when two consecutive sprays were performed. However, at 10 days after second spray, the fruit extract did not differ significantly from the control, but it was comparable in its effect to the insecticides, except abamectin and cyromazine. In greenhouse experiments, the pea leafminer larvae were found at higher densities on cucumber leaves located at the lower plant part (10–60 cm) compared to other leaf positions. The Melia fruit extract and the other pesticides significantly decreased the number of live larvae per cucumber leaf compared to the control, 10 days after each spray. The fruit extract, abamectin, cyromazine, imidacloprid and pyrazophos lowered the leafminer population significantly compared to the control, throughout the period of the experiments. However, the fruit extract was significantly less effective than these insecticides at the final count, 20 days after second spray. Abamectin and cyromazine consistently showed a significant decrease in number of larvae, in both field and greenhouse experiments. At certain periods of the experiments, Melia extracts were comparable in their efficacy to the tested commercial biorational and synthetic pesticides. Thus, they have a good potential to be used in the management of the pea leafminer. This is the first report for use of M. azedarach against L. huidobrensis.

The influence of an additional supply of ammonium to a nitrate containing hydroponic solution on the mineral nutrition of greenhouse rose plants (Rosa hybrida cv. ‘Lambada’) has been investigated. The effect on NPK uptake, mineral contents in roots and leaves as well as nitrate reductase (NR) and glutamine synthetase (GS) activities were examined. The addition of ammonium in a nutrient solution containing nitrate produced a total nitrogen uptake increase during shoot elongation, while in the absence of ammonium, nitrate uptake was lower during shoot elongation. Adding ammonium to the hydroponics solution caused an increase of potassium uptake while ammonium absorption was constant. Phosphate uptake was always higher in combined nitrate plus ammonium treatment, likewise in this treatment the most relevant effect on plant mineral content was the increase of P concentration in the roots. In both treatments with or without NH+4, free nitrate was notably higher in the roots than in leaves, indicating that nitrate reduction in rose plants takes place mainly in the leaves. NR activity in the leaves was higher when ammonium was present, whereas the root GS activity was similar in both treatments. The influence of ammonium on phosphate uptake and the subsequent effects on transport of other ions and enzymatic activities are discussed.

Available pasture, liveweight gain, milk yield and supplementary feeding of Awassi sheep were monitored for four seasons (1991/92 to 1994/95) on pasture fertilized with superphosphate between 1984 and 1990. The experimental plots received three rates of phosphate (0, 25 and 60 kg P2O5/ha) annually, but no application after September 1990. The experiment was grazed at low (1·1 sheep/ha per year) and high (2·3 sheep/ha per year) stocking rates. The experimental site was typical of communally owned grasslands within the cereal zone of west Asia, where cropping is not possible because of shallow, stony soil and steep slopes. Plots with residual phosphate contained significantly more herbage and supported heavier animal liveweights, especially in the first two seasons. Milk yield and lamb production were greater and the need for supplementary feeding was reduced due to increased herbage. The results suggest that benefits of residual phosphate on pasture and livestock production can be considerable and should be included when assessing the value of applying fertilizer to degraded marginal lands in west Asia. Provided that the stocking rates remain within the range tested in the study, the pasture would suffer no harm. However, the higher stocking rates now practiced in the spring under communal grazing might severely limit flowering and seed-set. The property right to own or use the grazing land is seen as a key factor, deserving attention from governments in west Asia in order to apply new technologies to improve degraded marginal lands.