Seasonal Dry Matter Production Research Articles

Annual and seasonal dry matter production, botanical species composition, and nutritive value of multispecies, permanent pasture, and perennial ryegrass swards managed under grazing

AbstractReduced reliance on inputs such as fertilizer is fundamental to sustainable grazing systems. This two‐year study compared four sward types, including multispecies swards (MSS), for herbage dry matter (DM) production, species contribution to DM, and herbage nutritive value under grazing. The systems were: (1) Lolium perenne L. monoculture (PRG; 170 kg N ha−1 year−1); (2) permanent pasture (PP; 135 kg N ha−1 year−1), (3) six species sward consisting of two grasses, two legumes and two herbs (6S; 70 kg N ha−1 year−1), (4) twelve species sward consisting of three grasses, four legumes and five herbs (12S; 70 kg N ha−1 year−1). Herbage samples were collected for DM yield, botanical composition, and nutritive value. Mean annual DM production for PRG, PP, 6S, and 12S was 11,374, 8526, 13,783, and 13,338 kg DM ha−1 respectively. Herb proportions decreased in 6S and 12S from 2020 to 2021 while grass proportions increased. Mean crude protein levels were similar across all systems (p > 0.05), with higher ash content in 6S and 12S compared to PRG (p < 0.001). Organic matter digestibility was lowest in PP compared to PRG (p < 0.001) while neutral detergent fibre content of PP and PRG were greater than 6S and 12S (p < 0.001). Water soluble carbohydrate content was highest in PRG (p < 0.0001). Over 2 years, MSS delivered increased herbage DM yield and nutritive quality relative to PRG and PP swards, from reduced N inputs. However, maintenance of the herb component of MSS is a challenge.

AGRONOMY OF MULATO GRASS CULTIVAR (BRACHIARIA SP.) IN GRAZING CONDITIONS IN QUINTANA ROO, MEXICO

The objective of this study was to determine the behavior of Mulato grass under grazing conditions in Quintana Roo. This work was carried out in the Chetumal Experimental Field of INIFAP in Quintana Roo, which is located 25 km from Chetumal, in the vicinity of the Juan Sarabia ejido, on km 25 of the Chetumal federal highway. For the development of the study, two hectares were used, 1 ha of Brachiaria humidícola (Chetumal) and another of Brachiaria sp. (mulato). For each type of pasture, three recently weaned steers of the Holstein for Zebu and Swiss for Zebu breeds with an approximate initial weight of 242 ± 3 kg were used the variables measured were seasonal dry matter production, plant cover and height, forage supply, and the botanical composition of the meadow. Subsequently, the steers were changed by load adjustment and the weight gain was determined. The design used was totally randomized with three repetitions per treatment and the analysis of the information was carried out through the ANOVA. No differences (P≥0.05) were found in the number of plants 12 weeks after establishment. For the coverage parameter, differences (P≤0.05) were observed with values ​​of 89% and 77 for Chetumal and mulatto grass, respectively. The values ​​of weight gain among the grasses under study (650 vs 675 for Chetumal and mulatto, respectively) did not indicate differences (P≥0.05) between them. Therefore, mulatto grass should be considered as an option for livestock in the state.

Use of the VegSyst model to simulate seasonal dry matter production, N and K uptake and evapotranspiration in greenhouse soil-grown tomato in Uruguay

The VegSyst model, initially developed for nitrogen (N) and irrigation recommendations for greenhouse-grown vegetable crops in southeastern Spain, was calibrated and validated for greenhouse tomato cultivated in soil in Uruguay (South America) for autumn and spring growing seasons. Additionally, the performance of the recalibrated VegSyst model was compared to the calibration for tomato grown in Almeria greenhouses of VegSyst model V3. Five tomato crops, three autumn and two spring crops grown in 2019, 2020 and 2021, were used for model calibration (Spring-19 and Autumn-20) and validation (Autumn-19, Spring-21 and Autumn-21). A major change to the existing VegSyst model (V3) was the incorporation of the Hargreaves-Samani equation adapted to plastic greenhouses to estimate ETo. The recalibrated VegSyst model accurately simulated dry matter production (DMP), ETc, and crop N and K uptake over time for autumn and spring growing seasons. Using the original VegSyst V3 calibration, acceptable results were obtained for DMP and N uptake. A new dilution curve for N content was included. It was derived from pooled data and was described by the power equation %N = 3.4117 x DMP−0.153 (R2 of 0.84). Both, this dilution curve and the critical N curve of VegSyst V3 provided accurate simulation of crop N uptake. Therefore, both can be used in Uruguayan conditions. K uptake simulations were accurate according to the statistical indices used. This was despite that the K dilution curve of %K = 4.359 x DMP−0.005 had a low R2 value. Moreover, simulation with this K dilution curve provided better results than with the dilution curve of VegSyst V3. A decision support system based on the recalibrated VegSyst model will be developed to assist Uruguayan farmers and advisers. It will provide calculation of daily irrigation needs and nutrient concentration tailored to each crop and greenhouse.

Agronomic performance of ten perennial ryegrass varieties on commercial grassland farms

AbstractLittle information is available on the phenotypic performance of perennial ryegrass varieties when exposed to grazing conditions on commercial grassland farms. Grass varieties are classically evaluated in mechanically defoliated plot systems which, although designed to mimic grazing conditions, do not fully capture the range of stresses or interactions that a sward is subjected to under commercial settings or over any period longer than 4 years. The evolution of technology in the form of PastureBase Ireland has led to agronomic data of individual paddocks being made available for analysis over multiple years. Data used in the current study consisted of dry matter (DM) production and ground score data across a 7-year period from ten perennial ryegrass varieties grown as monocultures in 559 paddocks on 98 commercial farms. The results demonstrated how perennial ryegrass variety is associated with a range of agronomic performance traits on commercial farms; including total and seasonal DM production, grazing DM production and number of grazing events. Varieties with the highest total DM production also had the highest spring and mid-season DM production; autumn DM production was associated with the interaction between variety and year. The highest producing variety in the study, AberGain, produced 1342 kg DM/ha/year more than the mean of all other varieties. Variety differences manifested themselves as swards aged, with some varieties increasing in total DM production while others reduced in total DM production. The current work provides a basis for the consideration of on-farm variety assessment in the composition of future variety evaluation protocols.

Calculation of sheep and beef economic weightings for the seasonal dry matter production trait for use in a forage-cultivar selection decision-support tool

Development of an independent forage-cultivar selection decision-support tool (DST) could transfer substantial benefits to sheep and beef (S&B) farmers. This study took a first step toward development of a S&B DST by describing and assessing one method of calculating S&B forage trait economic weightings. The ‘change in livestock production’ economic weighting method was applied to the Otago/Southland Breeding Finishing Farm Class in this study. The trait economic weightings for the seasonal dry matter (DM) production trait were applied to cultivar performance trial data using the DairyNZ Forage Value Index (FVI) framework. Analysis indicated the rankings of perennial ryegrass cultivars using the DST method varied from those calculated using the DairyNZ FVI when using the same seasonal DM production data. It was concluded the change in livestock production method is an option for calculating the economic value of traits for evaluation of perennial ryegrass cultivars that are more applicable to S&B farmers. However, this method should be applied to a wider range of S&B Farm Classes before a decision is made as to its suitability for the New Zealand S&B industry.

Impact of seasonal nitrogen fertilisation on production characteristics of a mixed grass pasture in the Western Cape province of South Africa

Pasture production in the Western Cape has traditionally been based on temperate species producing the majority of fodder during spring and autumn after which dry matter production decreases in winter. To investigate seasonal fertiliser nitrogen (N) management strategies to optimise seasonal dry matter production, a mixed grass pasture consisting of perennial ryegrass (Lolium perenne), tall fescue (Festuca arundinacea) and cocksfoot (Dactylis glomerata) was established. The effect of fertiliser N (0, 20, 40, 60 and 80 kg N ha−1) and season of application (spring, summer, autumn and winter) were evaluated. Dry matter production was significantly (p = 0.05) the highest in spring (year 1) and in spring and summer (year 2) with application of 60–80 kg N ha−1. Botanical composition was mainly determined by season of application, whereas crude protein content was characterised by a strong interaction between season of N application and application rate. It is concluded that, excluding winter, seasonal application of N can be used as a management tool to increase dry matter production. It is recommended that 40 kg N ha−1 during autumn and spring and 60 kg N ha−1 during summer should be applied to grass pastures under irrigation in the Winelands subregion of the Western Cape.

Seasonal dry matter production, botanical composition and forage quality of kikuyu over-sown with annual or perennial ryegrass

The seasonal growth and low forage quality of kikuyu restrict milk production. The aim of this study was to determine the yield and nutritional value of irrigated kikuyu over-sown with perennial, Italian or Westerwolds ryegrass grazed by dairy cows. The three pasture systems reached optimum growth during different months and seasons. Lowest growth rates occurred during winter. Peak growth rates occurred during spring for the Italian ryegrass–kikuyu, summer for the Westerwolds ryegrass–kikuyu, and late spring and early summer for perennial ryegrass–kikuyu pasture. All three pasture systems had similar total annual dry matter yields (kilograms dry matter [DM] per hectare) during year 1, but the perennial ryegrass–kikuyu pasture achieved a higher annual DM yield during year 2. As kikuyu density increased in kikuyu–ryegrass pastures from winter to summer, the DM and neutral detergent fibre content increased, whereas the metabolisable energy content decreased. All three treatments were deficient in calcium during all seasons and in phosphorus during summer and autumn as a pasture for high-producing dairy cows.

Productivity evaluation of Medicago sativa cultivars under irrigation in a semi-arid climate

Many Medicago sativa cultivars are available in South Africa, each with unique characteristics. This study evaluated 26 cultivars under irrigation on two ecotopes in terms of number of cuttings, dry matter (DM) production, seasonal DM production curve, DM production curve over lifespan and plant density, over nine growing seasons. The production per cutting decreased from 3 624 and 3 401 kg DM ha−1 to 902 and 864 kg DM ha−1 on soil of medium and high clay content, respectively. The production peaked during the second and third growing seasons, with respectively 22 524 and 22 640 kg DM ha−1 on the medium-clay-content soil, and 20 442 and 20 352 kg DM ha−1 on the high-clay-content soil. Cumulative production over nine growing seasons varied from 131 762 to 169 408 kg DM ha−1 on the medium-clay-content soil and from 84 407 to 130 447 kg DM ha−1 on the high-clay-content soil. The relationship between production and dormancy class was only signifi cant after four to five growing seasons. Dormancy class six to eight seems to be more productive in this environment. The cultivars KKS 3864 and Eureka can be considered the best DM-producing cultivars under irrigation in this environment.

Early season dry matter production of three hybrid ryegrass (Lolium boucheanum) and two perennial ryegrass (Lolium perenne) cultivars

Hybrid ryegrass (HRG) is purported to have high overwinter growth characteristics and may have a role in Irish grassland systems. In a 3-year small-plot study at Fermoy, Cork, Ireland, the dry matter (DM) production and herbage quality of HRG cultivars in early spring were compared with diploid and tetraploid perennial ryegrass (PRG) cultivars. Treatments comprised ryegrass cultivars × defoliation managements × defoliation heights in a 5 × 3 × 2 factorial arrangement. The cultivars were Navan (tetraploid PRG), Foxtrot (diploid PRG), Foyle (tetraploid HRG), Brutus (diploid HRG) and Belleek (tetraploid HRG). Defoliation dates were: (A) 2 February and 20 April; (B) 2 February, 3 March and 20 April; and (C): 2 February, 23 March and 20 April. Defoliation heights were 4 and 7 cm, applied across each management. The HRG cultivars yielded similarly to cv. Navan on 2 February. Cumulative spring DM production was higher in cvs. Brutus and Belleek than all other cultivars. During this period, the managements A and B had similar DM yields (2765 kg DM ha−1) but were greater than management C. Defoliating swards to 4 cm height increased DM yield compared with 7 cm height. Organic matter digestibility of grass at the silage-harvest growth stage was greater for PRG cultivars. The study indicates that early spring growth of the three HRG cultivars evaluated here was not sufficiently greater than the tetraploid PRG cv. Navan to compensate for their poorer midseason sward quality.

Light and Moisture Competition Effects on Biomass of Red Clover Underseeded To Winter Wheat

Red clover (Trifolium pratense L.) use as an underseeded cover crop in winter cereals has declined due to inability of growers to consistently establish uniform stands. The objective of this study was to assess the effect of light and soil moisture competition on underseeded red clover establishment and end of season dry matter production. Field trials were conducted at multiple locations in 2005 and 2006 in Ontario, Canada. Wheat (Triticum aestivum L.) N rate (67 and 135 kg N ha−1) and row thinning treatments (19‐cm rows, every third 19‐cm row removed at the 4–5 leaf stage) were used to alter light penetration and soil moisture competition. The high N rate and row thinning treatments consistently reduced light penetration, beginning as early as wheat stem elongation initiation, but had no effect on soil gravimetric moisture content. Soil moisture was primarily affected by location and year. Red clover dry weight in 2005, a relatively dry year, ranged from 688 to 1184 kg ha−1, and in 2006, a relatively wet year, ranged from 2336 to 2805 kg ha−1. Average final red clover stand count was 23 plants m−2 in 2005 and 55 plants m−2 in 2006. In 2005, plant mortality occurred before wheat anthesis. In both years, and at most locations, red clover final dry weight was positively correlated with light penetration, again beginning as early as initiation of wheat stem elongation. Final red clover dry weight in both years and red clover stand count in 2005 were correlated with soil gravimetric water content during wheat anthesis, but this was primarily due to location and year effects. Although both light penetration through the wheat canopy and soil moisture influence biomass production of underseeded red clover, soil moisture has the greater influence and is altered very little by wheat management.

Kikuyu over-sown with ryegrass and clover: dry matter production, botanical composition and nutritional value

The seasonality of growth and low nutritional value of kikuyu (Pennisetum clandestinum) pasture restrict milk production. The aim of the study was to determine the dry matter yield, botanical composition and nutritional value of irrigated kikuyu over-sown with annual ryegrass (Lolium multiflorum var. westerwoldicum), white clover (Trifolium repens) and red clover (T. pratense) or a mixture of perennial ryegrass (Lolium perenne) with white and red clovers under intensive grazing conditions with dairy cows. The incorporation of annual ryegrass, perennial clover or perennial ryegrass–clover into kikuyu pasture changed the seasonal fodder flow and increased the spring dry matter (DM) production. The over-sowing of kikuyu with annual ryegrass had no effect on the DM production of kikuyu during the summer and autumn. Kikuyu and kikuyu–ryegrass, fertilised with nitrogen fertiliser, had a higher DM production rate than kikuyu–clover pastures. Kikuyu–ryegrass pasture transformed from ryegrass-dominant in spring to kikuyu-dominant in summer and only kikuyu in autumn. This led to a decrease in metabolisable energy (ME) and increase in neutral detergent fibre (NDF) content of the pasture during spring, summer and autumn as kikuyu became more dominant. The clover content of kikuyu over-sown with clover decreased annually but was still higher than 30% at the end of two years after establishment. As the kikuyu content of the kikuyu–clover pastures increased, the seasonal growth rate changed from a low autumn growth (37.9 kg DM ha−1 d−1) in the first year to a higher autumn growth (48.5 kg DM ha−1 d−1) in the second year. The over-sowing of kikuyu with clover resulted in lower DM production and NDF values and higher crude protein (CP), ME and calcium (Ca) values. The lowest CP content in kikuyu–ryegrass pasture was during summer and autumn when kikuyu was dominant. The Ca content of the grass pastures (kikuyu and kikuyu–ryegrass) was low. The phosphorus (P) content of both the kikuyu–clover and grass pastures exceeded the requirement needed for dairy production (0.38%). The mean Ca:P ratio of the kikuyu–clover pasture meets the 1.6:1 ratio needed by dairy cows. The kikuyu and kikuyu–ryegrass pasture had a Ca:P ratio lower than 1:1 and Ca supplementation would be needed for dairy cows. The incorporation of annual ryegrass, perennial clover or perennial ryegrass–clover into kikuyu pasture improved the seasonal DM production and nutritional value of the pasture.

Photoperiod Sensitivity of Rhizoma Peanut Germplasm

Short days are thought to alter dry matter (DM) partitioning in rhizoma peanut (Arachis glabrata Benth.). Under controlled environmental conditions, six lines of rhizoma peanut germplasm (cultivars Florigraze and Arbrook; Florida lines Ecoturf, Arbrook Select, and Arblick; and PI 262826) were exposed to natural and extended photoperiod regimes (15 or 18 h). The study started 21 Sept. 2000 and ran until the following May; aboveground DM was harvested five times. The following year the same lines were transplanted into the field, where they received either natural light or 15 h extended photoperiod conditions between 20 Sept. 2001 and 19 Apr. 2002 and again during the winter of 2002–2003. In the field, cover and DM was determined on approximately 9 wk intervals. In the controlled environment study, both extended photoperiod treatments increased DM yield, but the 18 h treatment was most consistent across selections and dates. The February response was greatest when there was greater than fivefold increase across selections for the 18 h treatment above natural photoperiod (2.80 vs. 0.52 g/pot, respectively). In the field, percent cover was enhanced by extended photoperiod for all selections except Ecoturf by the second sampling date after the lights were turned on (avg. 90 vs. 38% cover, respectively, for extended and natural photoperiod). Cover differences persisted until June 2002. Dry matter yield also was increased by treatment during the fall of both years. These studies suggest that selection for late and early season DM production in rhizoma peanut will select for photoperiod insensitivity.

Effect of defoliation management, based on leaf stage, on perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under dryland conditions. 1. Regrowth, tillering and water‐soluble carbohydrate concentration

AbstractA field study was undertaken between April 2003 and May 2004 in southern Tasmania, Australia to quantify and compare changes in herbage productivity and water‐soluble carbohydrate (WSC) concentration of perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under a defoliation regime based on leaf regrowth stage. Defoliation interval was based on the time taken for two, three or four leaves per tiller to fully expand. Dry‐matter (DM) production and botanical composition were measured at every defoliation event; plant density, DM production per tiller, tiller numbers per plant and WSC concentration were measured bimonthly; and tiller initiation and death rates were monitored every 3 weeks. Species and defoliation interval had a significant effect (P < 0·05) on seasonal DM production. Prairie grass produced significantly more (P < 0·001) DM than cocksfoot and ryegrass (5·7 vs. 4·1 and 4·3 t DM ha−1 respectively). Plants defoliated at the two‐leaf stage of regrowth produced significantly less DM than plants defoliated at the three‐ and four‐leaf stages, irrespective of species. Defoliation interval had no effect on plant persistence of any species during the first year of establishment, as measured by plant density and tiller number. However, more frequent defoliation was detrimental to the productivity of all species, most likely because of decreased WSC reserves. Results from this study confirmed that to maximize rates of regrowth, the recommended defoliation interval for prairie grass and cocksfoot is the four‐leaf stage, and for perennial ryegrass between the two and three‐leaf stages.

Starter Nitrogen Fertilizer Management for Continuous No‐Till Corn Production

High residue levels provide excellent erosion control but can result in cool, wet seedbeds creating a situation where starter fertilizer may be beneficial. Research was conducted from 1999 to 2001 evaluating N rates in starter containing N, P, K, and sometimes S; and different starter fertilizer placements for continuous no‐till corn (Zea mays L.). Placements consisted of direct seed contact, dribble over‐the‐row, and a subsurface band (5 cm below and 5 cm to the side of the seed row). Nitrogen rates for direct seed and dribble placements were 11, 22, 45, and 56 kg N ha−1; and 34, 67, 101, and 134 kg N ha−1 for the subsurface placement. Nitrogen was balanced at 168 kg ha−1 on all treatments, including a no‐starter check using broadcast ammonium nitrate at planting. Addition of S in starter was evaluated with subsurface placement. Starter fertilizer, regardless of placement, often increased early season dry matter production and significantly increased grain yields. Increasing N above 22 kg ha−1 in direct seed contact did not increase yields and significantly reduced stands 2 of 3 yr. Stands were unaffected with higher N rates in dribble over‐the‐row and subsurface placements; however, applying N above 11 and 34 kg ha−1, respectively, resulted in little added yield benefit. Inclusion of 11 kg S ha−1 in a subsurface starter fertilizer sometimes increased early season dry matter production, grain yield, and nutrient uptake. Results suggest starter fertilizer is an effective, efficient way of stimulating early growth and improving yields of continuous no‐till corn in Kansas.

Seasonal dry matter production of Lotus corniculatus in a dryland commercial sheep pastoral system

Lotus corniculatus (Birdsfoot trefoil, 'Grassland Goldie') may have a role in dryland pastoral systems in New Zealand, but there is little information available on its production under sheep grazing in these conditions. Dry matter (DM) production of L. corniculatus was measured monthly for 2 consecutive years in a systems approach experiment comparing it with perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture in the Wairarapa on the east coast of the North Island. The total DM produced for 2 years was 8.5 and 10.5 t /ha for L. corniculatus compared with 7.3 and 9.9 t /ha for pasture. Also, the moderate concentration of CT (18- 29 g/kg DM) in L. corniculatus has been shown to increase sheep productivity (Wang et al. 1996ab; Min et al. 1999, 2001). This production advantage, combined with improved sheep performance, supports the potential use of L. corniculatus as a specialist forage in dryland areas. Key words: condensed tannins, perennial ryegrass, Lolium perenne, white clover, Trifolium repens, pasture.

Perennial grasses of Mediterranean origin offer advantages for central western Victorian sheep pasture

Perennial ryegrass, tall fescue, cocksfoot and phalaris were evaluated under a rotational grazing regime in the 600 mm rainfall region of western Victoria. Over 4 years, seasonal dry matter production, persistence and nutritive value were assessed. Several selected lines and commercial cultivars were compared. Melik selection tall fescue and Sirosa phalaris significantly (PPP The benefits of Mediterranean genotypes of perennial grasses for improving winter yield and plant longevity is discussed in relation to the need to maximise pasture productivity and improve pasture longevity in environments with a short growing season.

Influence of Seed Quality on Field Establishment and Forage Yield of White Clover (Trifolium repens L.)

AbstractTwo seed lots of white clover (Trifolium repens L.) cultivar ‘Makibashiro’ classified as high and poor quality seed lots, based on the speed of germination (T50), were used to examine the influence of seed quality on field establishment and forage yield. Field emergence rate was estimated approximately three weeks after sowing and found that plots sown with high quality seeds (Lot 1) had 452 seedlings m‐2 compared with 392 seedlings in the plots sown with low quality seed lot (Lot 2), but the difference was not significant. However, plant density in autumn (November, 1993), 3 months after sowing, was significantly (P < 0.05) higher in the plots of the Lot 1 seed than that from the Lot 2 seed. The percentage of clover plants surviving over the winter from Lot 1 plots was 55% compared with 39% from the Lot 2 plots, but the difference was not significant. Total forage yield in Lot 1 plots harvested in July and monthly intervals to October, was significantly increased by 44% (P < 0.05) over that of Lot 2 plots, but this greater forage yield in high seed quality seed lot plots was produced early in the season. The results strongly imply that the primary advantage to be gained from high quality seed is an improved field establishment, which led to increased yield of clover. In Lot 1 plots, the percentage of weed dry matter in all the four harvests remained below 1% of die seasonal dry matter production, whereas in Lot 2 plots die percentage of weed dry matter ranged from 3.3–16.9%.

Agronomic Performance of Winter versus Spring Wheat

AbstractRecent advances in crop management have enabled the production of winter wheat (Triticum uestivum L.) in most of the Canadian prairies. The agronomic performance of dominant hard red winter and highq‐uality hard red spring wheat cultivars was compared in semiarid and dry subhumid regions of Saskatchewan. In 15 trials, winter wheat (WW) outyielded spring wheat (SW) by an average 36%, and in three trials, ‘Norstar’ WW yielded 26% higher than the high‐yielding semidwarf SW, ‘HY 320.’ Protein yield was higher for WW in two of 15 trials and protein concentration was always higher for SW. Higher grain yield of WW was attributed mainly to the production of a higher kernel number per square meter (KNO). Crop development rate, aerial dry matter production, evapotranspiration (ET), and water use efficiency (WUE), were measured for Norstar WW and ‘Katepwa’ SW in six trials grown between 1986 and 1988. The period between Zadoks growth stage (ZGS) 21 and 65 was 4 to 14 d longer for Norstar than for Katepwa. Average daily air temperature between ZGS 21 and 65 was 2.6°C higher for Katepwa, and daily air temperature during this period was negatively correlated with KNO in both cultivars. Early season dry matter production was highest for Norstar. These early season cultivar differences gradually disappeared and, with the exception of two trials, total dry matter was similar by crop maturity. Harvest index was significantly higher for Norstar in five of six trials. Seasonal ET patterns were similar for Norstar and Katepwa, except in three of six trials where ET in early May was significantly higher for the WW cultivar. The WUE for dry matter production, grain yield and grain protein yield was consistently higher for Norstar.

Breeding perennial ryegrass for agriculture

Perennial ryegrass has become the most widely sown perennial forage grass in temperate regions due to its combination of high digestibility and tolerance of grazing. The primary objectives in breeding for agricultural use are to improve total and seasonal dry matter production over a range of fertiliser inputs, digestibility, persistency, freezing tolerance and drought or heat tolerance. Adequate seed production and resistance to a wide range of diseases and pests is also necessary. Improvements in productivity and persistency so far have been achieved mainly by hybridisation and recurrent selection using the polycross method and by the use of polyploidy. Further improvements in freezing tolerance, drought and heat tolerance and, for some localities, resistance to pests and snow moulds are required to extend the geographic range of the species. Modern cultivars show little improvement in leaf or stem digestibility but a high magnesium variety is now available. Perennial ryegrass breeding is at an early stage and prospects for further progress appear good.

Dryland corn response to tillage and nitrogen fertilization. I. Growth‐yield‐N relationships

Abstract Crop response to fertilizer nitrogen (N) is dependent upon tillage management. This study was conducted to determine how tillage rotation influences non‐irrigated crop growth, N uptake and yield. The effects of tillage rotation, N rate and N timing schedule on early season dry matter production and N uptake, ear leaf N concentration at silking, and yield of corn [Zea mays (L.) Pioneer 3378] were investigated at Painter, VA, on an Altavista loam (fine‐loamy, mixed, thermic Aquic Hapludult). In 1986, maximum yields achieved in the 6‐year continuous no till (NT) [5.82 Mg/ha] and first year no till (AT) [5.64 Mg/ha] were significantly greater than that of the 6‐year continuous conventional till (CT) [3.67 Mg/ha], but no yield differences were obtained in the drier 1987 season. A higher rate of N fertilizer was required to obtain maximum yield in the first year no till (168 kg N/ha) than in the NT (112 kg N/ha) during 1986. Early 1986 N uptake and growth response with and without N at planting increas...