Biomass yield and nutrient content of a tropical mulberry forage bank: effects of season,harvest frequency and fertilization rate

Effects of season (SEAS), organic fertilization with laying hen manure (N) and harvest frequency (FREQ) on forage yield and composition were evaluated in a high‐density mulberry forage bank, established under low‐input tropical farming conditions. The experiment, replicated over two consecutive years, was arranged in 18 treatments resulting from a 3 × 3×2 factorial design which combined three FREQ (60, 90 and 120 d), 3 N rates (100, 300 and 500 kg N ha^?1 year^?1) and the two seasons (RAIN and DRY). Forage yield, leaf‐to‐stem ratio, the edible fraction (EDIB, %), nutrient content and the maturity indexes were monitored. Either forage yield or qualities by plant fraction were strongly affected by SEAS, FREQ, N rate and by their interactions. Effects of FREQ and N were modulated by SEAS. Increasing FREQ during RAIN negatively affected EDIB yield and quality after 90 d, while increasing ligneous fraction. During DRY, longer FREQ allowed higher total forage and EDIB yields. Leaves were more abundant in RAIN, and its yield was increased with fertilization but only during this season. Maturity indexes were higher in DRY than in RAIN. Under the conditions of this experiment, harvesting at 60 and 90 d in RAIN and DRY, respectively, with an N rate of 300 kg N ha^?1 year^?1 seems the best agronomic choice for an optimal compromise between forage yield and nutritive value.     

The efficiency of nitrogen in cattle manures when applied to a double‐annual forage cropping system

The use of cattle manure (CM) for fertilization presents challenges for optimizing nitrogen (N) use. Our work aimed to assess N efficiencies, in a 6‐year experiment with three biennial rotations of four crops: oat–sorghum (first year) and ryegrass–maize (second year) in a rainfed humid Mediterranean area of Spain. Fertilization treatments included the following: control (no N), 250 kg mineral N ha^?1 year^?1 (250MN), three CM rates (supplying 170, 250 and 500 kg N ha^?1 year^?1) and four treatments where the two lowest CM rates were complemented with either 80 or 160 kg mineral N ha^?1 year^?1. Treatments were distributed randomly in each of three blocks. Maximum dry‐matter yield (~44–49 t ha^?1 rotation^?1) was achieved in the third rotation, and only the control and the 170CM yielded significantly less. Within the limitations of the EU Nitrate Directive, the N steady state supply of 170CM always requires a complement of mineral N (80 kg N ha^?1) to maximize N agronomic efficiency. The maximum N‐fertilizer replacement value (250CM vs. 250MN) was 0·67, without significant differences between the two treatments in other N‐related efficiency indexes, which indicates that plants took advantage of residual‐N effects. Nitrogen losses by leaching in the 250CM treatment were around 5–7% of the N applied. This reinforces the sustainability of manure recycling in long cropping seasons.     

Phyto-purification of livestock-derived organic waste by forage rice under subtropical climate

Soil and water pollution caused by organic waste is a concern for livestock-breeding areas. Nitrogen balance in a paddy-field water-purifying system in which cattle feces were applied was studied for 4 years to assess the suitability of the system for a subtropical area, Japan. Three successive harvestings using ratoon of forage rice following one rice transplanting were conducted with chemical fertilizer and high and low rates of cattle-feces application. Nitrogen load was 81.3–495.0 kg N ha^?1 year^?1, while nitrogen uptake was highly dependent on the yield of the first harvesting. Annual variation of forage rice yields was large, ranging from 15.5 to 26.8 Mg ha^?1 owing to fluctuation in the yield at second and later harvestings. On average, nitrogen was lost by leaching at a rate of 2.3–3.4 kg N ha^?1 year^?1. The nitrogen content in soil at a depth of 0–5 cm increased up to 12.2 kg N ha^?1 over the 4-year period compared with that before the field experiment. However, continuous application of cattle feces could slightly increase the nitrogen content in soil at a depth greater than 35 cm. Our results showed the ability of flooded forage rice to remove nitrogen at up to 320.1 kg ha^?1 year^?1 for a field to which cattle feces were applied. Further investigation is needed to produce a high and stable yield at second harvesting each year, to prevent the accumulation of soil nitrogen, and to assess gaseous nitrogen loss.     

Bahiagrass (Paspalum notatum Flugge) management combining nitrogen fertilizer rate and defoliation frequency to enhance forage production efficiency

Bahiagrass (Paspalum notatum Flugge) pastures are widespread in warm climates worldwide and respond to nitrogen (N) fertilizer. Nitrogen fertilization has recently decreased because of increased cost and concerns regarding excessive N in the environment. Responses of bahiagrass to treatments representing three alternative levels of pasture management were assessed. Treatments, each including 56 kg N ha^?1 applied for each growth period, were as follows: (i) six harvests with a total of 336 kg N ha^?1 annually (referred to as intensive management), (ii) three harvests with 168 kg N ha^?1 annually (intermediate management) and (iii) two harvests with 112 kg N ha^?1 annually (extensive management). The intensive management produced the most forage with the highest nutritive value. Intermediate management, with only half the amount of N fertilizer, produced at least 80% of the forage yield each year as the intensive management treatment (4‐year average of 8236 vs. 9122 kg ha^?1 for the intermediate and intensive management treatments respectively) with forage of acceptable nutritive value for some classes of livestock. Limited forage production from the last harvest each year restricts autumn management opportunities, even though crude protein concentration was usually sufficient for some classes of livestock. Extended growth periods, as those that occur with the less‐intensive management treatments, provide opportunities to accumulate forage for late‐season grazing. Matching livestock enterprises to the forage produced, particularly in terms of nutritive value, can contribute to favourable livestock production responses from a range of bahiagrass pasture management approaches.     

The effect of stocking rate and calving date on grass production,utilization and nutritive value of the sward during the grazing season

A 2‐year whole‐farm system study compared the accumulation, utilization and nutritive value of grass in spring‐calving grass‐based systems differing in stocking rate (SR) and calving date (CD). Six treatments (systems) were compared over two complete grazing seasons. Stocking rates used in the study were low (2·5 cows ha^?1), medium (2·9 cows ha^?1) and high (3·3 cows ha^?1), respectively, and mean CDs were 12 February (early) and 25 February (late). Each system had its own farmlet of eighteen paddocks and one herd that remained on the same farmlet area for the duration of the study. Stocking rate had a small effect on total herbage accumulation (11 860 kg DM ha^?1 year^?1), but had no effect on total herbage utilization (11 700 kg DM ha^?1 year^?1). Milk and milk solids (MS; fat + protein) production per ha increased by 2580 and 196 kg ha^?1 as SR increased from 2·5 to 3·3 cows ha^?1. Milk production per ha and net herbage accumulation and utilization were unaffected by CD. Winter feed production was reduced as SR increased. Increased SR, associated with increased grazing severity, resulted in swards of increased leaf content and nutritive value. The results indicate that, although associated with increased milk production per ha, grazed grass utilization and improved sward nutritive value, the potential benefits of increased SR on Irish dairy farms can only be realized if the average level of herbage production and utilization is increased.     

Yield response of long-term mixed grassland swards and nutrient cycling under different nutrient sources and management regimes

Abstract The response of a long‐term, mixed‐species hayfield in Maine, USA, to commercial fertilizers and liquid dairy manure was evaluated over a 6‐year period, including the effects on yield, nutrient concentration and cycling, forage species composition and soil nutrient levels. Nutrient treatments included an unamended control, N fertilizer, NPK fertilizer and liquid dairy manure (LDM). The application rates of plant‐available N, P, and K were constant across treatments. Application of nutrients in any form increased forage yield, generally by 2–4 t dry matter (DM) ha^?1 year^?1. Yield from NPK fertilizer was 0·05–0·25 higher than from LDM, due to differences in N availability. Yield responses to P and K were minimal and there appeared to be no difference between P and K in fertilizer and manure. The forage sward became increasingly dominated by grass species as the experiment progressed; application of P and K in fertilizer or LDM allowed Agropyron repens to increase at the expense of Poa pratensis. Forage nutrient removal accounted for all applied N and K, and nearly all applied P, throughout the study period, demonstrating the important role these forages can play in whole‐farm nutrient management.     

Effect of applications of organic solid cattle manure on Hungarian vetch and barley intercropping mixtures grown on soils of different depths

Sloping fields on soils of shallow depth to tillage are commonly left uncultivated in many parts of the world. This study was conducted to compare the effects on morphological traits, dry‐matter (DM) yield, legume ratio (LR), crude protein content (CP), crude protein yield (CP yield) and mineral concentrations (N, P, K, S, Ca, Cu, Fe, Mg, Mn, Na, B and Zn) of Hungarian vetch (Vicia pannonica Crantz.) and barley (Hordeum vulgare L.) grown in intercropping mixtures in response to three rates of organic solid cattle manure application (M₀: 0, M₁: 10, M₂: 20 t ha^?1). Experimentation was conducted on soils of two different soil depths [shallow (8–12 cm; low‐medium erosion risk) and normal soil depth (18–22 cm; no erosion risk)] on a sloping field in the 2006–2007 and 2007–2008 growing seasons at Gumushane, Turkey. Herbage harvested on the shallow depth area had 22–73% less DM yield, 14–72% less CP yield, 6–9% greater CP content and generally higher minerals contents than herbage from the normal soil depth area. Cattle manure applications increased DM yield by about 23%, increased CP content and CP yield, and also increased the contents of most minerals in herbage of the intercropping mixtures, relative to the control, averaged over the two soil depths. It is suggested that, for areas with shallow soil depths that are prone to erosion, plant cover should be used for forage production, and that fertilization with solid cattle manure at 20 t ha^?1 can support production of quality forage of acceptable DM yield.     

Effects of nitrogen application rate on productivity,nutritive value and winter tolerance of timothy and meadow fescue cultivars

Finnish N fertilizer application regulations for forage grasses are based on field experiments mainly conducted in the 1960–1970s with cultivars and management practices typical of the time. In order to update the yield response function of N, to make it better suited to current grassland farming, field experiments were conducted at two sites in 2015–2017 with two cultivars of timothy (Phleum pratense L.) and one of meadow fescue (Festuca pratensis Huds.). Dry matter (DM) yield, nutritive value and N balance were evaluated, with N application levels 0, 150, 200, 250, 300, 350, 400 and 450 kg N ha⁻¹ year⁻¹. The grasses were harvested three times per season. The data indicate that the DM yield response was significantly stronger, and N was used more efficiently for DM production than earlier without compromising the nutritive value, especially during the first two years. The third harvest produced on average 23% of the annual yield, utilizing N efficiently. N application rates below 350 kg N ha⁻¹ year⁻¹ did not cause substantial overwintering losses or lodging. The data indicate that with changing climate and improved cultivars and management practices, there is a need to modify the rates and timing of N application. The results suggest that N application levels could be increased by at least 50 kg N ha⁻¹ year⁻¹ from the current maximum accepted rate (250 kg N ha⁻¹ year⁻¹) without too high NO₃^- or CP concentrations in feed, or too high N balance that indicates increasing risk of N leaching.     

Rates and timing of nitrogen fertilizer application on yield,nutritive value and nutrient‐use efficiency of early‐ and late‐sown forage maize

The outcomes of previous studies have resulted in differing recommendations on the rate and timing of fertilizer N applications for forage maize. In order to gain an improved understanding of the role of N fertilizer, a field experiment was carried out to investigate the effects of time and rate of N application on total and plant‐fraction yield, nutritive value and efficiency of nutrient utilization in early‐ and late‐sown forage maize. Treatments included two sowing dates (early, late), two rates of N (0, 135 kg ha^?1) applied pre‐sowing (N1) and three rates of N (0, 79, 158 kg ha^?1) applied post‐sowing (N2) at the six‐leaf stage (V6). Application of N at N1 (N0 vs. N135) increased dry‐matter (DM) stover yield by 11% and total yield by 7%. Application of fertilizer N at N2 (N0 vs. N158) increased grain yield by 44% and total yield by 34%. Application of N2 also increased irrigation and total water‐use efficiency (WUE) from 30 to 40 and 46 to 61 kg DM ml ^?1 water respectively. Late sowing increased DM yield by 6%, but decreased WUE compared with early sowing. The results indicate that application of N at both N1 and N2 is essential to maximize total DM yield from forage maize, but application at V6 is recommended when N input is reduced.     

Biomass production and nutrient removal by tropical grasses subsurface drip‐irrigated with dairy effluent

Effluent lagoons on dairy farms can overflow and potentially pollute adjacent land and associated water bodies. An alternative solution to effluent disposal is needed by dairy operators in island environments. An attractive win‐win alternative is to recycle nutrients from this resource through effluent irrigation for forage grass production that minimizes environmental pollution. This study assessed biomass production and nutrient removal by, and high application rates to, tropical grasses that were subsurface drip‐irrigated with dairy effluent. Four grass species – Banagrass (Pennisetum purpureum K. Schumach.), California grass (Brachiaria mutica (Forssk.) Stapf.), Stargrass (Cynodon nlemfuensis Vanderyst) and Suerte grass (Paspalum atratum Swallen) – were subsurface (20–25 cm) drip‐irrigated with effluent at two rates based on potential evapotranspiration (ET_p) at the site (Waianae, Hawaii) ?2·0 ET_p (16 mm d^?1 in winter; 23 mm d^?1 in summer) and 0·5 ET_p (5 mm d^?1 in winter; 6 mm d^?1 in summer). Treatments were arranged in an augmented completely randomized design. Brachiaria mutica and P. purpureum had the highest dry‐matter yield (43–57 t ha^?1 year^?1) and nutrient uptake especially with the 2·0 ET_p irrigation rate (1083–1405 kg ha^?1 year^?1 N, 154–164 kg ha^?1 year^?1 P, 1992–2141 kg ha^?1 year^?1 K). Average removal of nutrients by the grasses was 25–94% of the applied nitrogen, 11–82% of phosphorus and 2–13% of the potassium. Average values of crude protein (90–160 g kg^?1), neutral detergent fibre (570–620 g kg^?1) and acid detergent fibre (320–360 g kg^?1) were at levels acceptable for feeding to lactating cattle. Results suggest that P. purpureum and B. mutica irrigated with effluent effectively recycled nutrients in the milk production system.     

Dry matter production, nutritive value and efficiency of nutrient utilization of a complementary forage rotation compared to a grass pasture system

In pasture‐based dairy farming, new sustainable systems that involve the annual dry matter (DM) production of grazed and conserved forage beyond the potential of grazed pasture alone are being sought. The objective of this experiment conducted in Australia was to compare a complementary forage rotation (CFR) for conservation and grazing, comprising an annual sequence of three crops, namely maize (Zea mays L), forage rape (Brassica napus L) and a legume (Persian clover, Trifolium repesinatum L or maple pea, Pisum sativum L), with a pasture [kikuyu grass (Pennisetum clandestinum) over‐sown with short‐rotation ryegrass (Lolium multiflorum L)] as a pasture control treatment. The experiment was a complete randomized block design with four replicates (～0·7 ha each). Annual dry‐matter (DM) yield over the 3 years averaged >42 t ha^?1 year^?1 for the CFR treatment and >17 t ha^?1 year^?1 for the pasture treatment. The high DM yield of the CFR treatment resulted from >27 t ha^?1 year^?1 from maize harvested for silage and >15 t DM ha^?1 year^?1 utilized by grazing the forage rape and legumes. Total input of nitrogen (N) and water were similar for both treatments, resulting in higher N‐ and water‐use efficiency for the CFR treatment, which was more than twice that for the pasture treatment. Overall, the nutritive value of the pasture treatment was slightly higher than the mean for that of the CFR treatment. The implications of these results are that a highly productive system based on the CFR treatment in conjunction with the use of pasture is achievable. Such a dairy production system in Australia could increase the total supply of feed resources grown on‐farm and the efficiency of use of key resources such as N and water.     

The effects of rates of application and sources of nitrogen on nitrate concentration in oat forage

A field experiment was conducted during the winter seasons of 1972–73 and 1973–74 to study the effects of rates of application (0, 100, 200 kg ha^?1) and sources of nitrogen (ammonium sulphate, calcium ammonium nitrate, urea, sulphur-coated urea and sulpha-thiazole-treated urea) on nitrate-N concentration in oat (Avena sativa L.) forage. N application increased the nitrate-N concentration, the effects being more marked when the rate was increased from 100 to 200 kg ha^?1 than when it was raised from 0 to 100 kg ha^?1. The highest nitrate-N concentration in the dry matter (> 0·16%) was obtained when calcium ammonium nitrate was applied at 200 kg ha^?1 N. Sulphur-coated urea gave the lowest nitrate-N concentration. In one year treatment of urea with sulphathiazole reduced nitrate-N concentration in oats forage.     

Production and nutritional value of sorghum and black oat forages under nitrogen fertilization

The effect of nitrogen (N) fertilization on the dry‐matter (DM) yield and nutritional value of sorghum (Sorghum sp., cv. Jumbo) and black oat (Avena strigosa cv., IPR 61) was investigated in the context of forage and livestock production in southern Brazil. Sorghum was cultivated with 0, 37·5, 75, 150, 225, 300 and 375 kg N ha^?1 during the summer crop seasons of 2010/11 and 2011/12. Black oat received 0, 40, 80, 120, 160, 200 and 240 kg N ha^?1 in the winter of 2011. According to the adjusted polynomial regression, sorghum DM yield increased in response to N up to 288 (12·9 t ha^?1) and 264 kg ha^?1 (5·6 t ha^?1) in 2010/11 and 2011/12 respectively. Crude protein (CP) content of sorghum was highest at 349 and 328 kg N ha^?1, but in vitro dry‐matter digestibility (IVDMD) was highest at 212–207 kg N ha^?1 in 2010/11 and 2011/12 respectively. Sorghum neutral detergent fibre (NDF) and acid detergent fibre (ADF) were not affected by N fertilization. In black oat, the maximum DM yield (6·0 t ha^?1) was obtained with 187 kg N ha^?1; the IVDMD, NDF and ADF were not affected by N fertilization, but the CP content increased up to 220 kg N ha^?1. It is concluded that these forage species can improve the year‐to‐year amount and quality of forage produced but high rates of N fertilizer are required to achieve high yields. Fertilizer N rates of 210–280 kg N ha^?1 in sorghum and 180 kg N ha^?1 in black oat in the crop rotation provide the greatest responses in DM yield consistent with good nutritional quality for livestock production.     

Is the nutritive value of tall fescue (Festuca arundinacea Schreb.) related to the accumulated forage mass?

The aim of this work was to investigate whether neutral detergent fibre (NDF) and dry‐matter digestibility (DMD) are related to tall fescue accumulated forage mass (AFM) and to assess the relevance of environmental variables to predict the nutritive value of tall fescue swards. Three experiments were carried out in Pergamino, Argentina. To obtain swards with different amounts of AFM, two N levels and two irrigation regimes were applied in the spring after sowing and the autumn of the next year. In spring and autumn, AFM, NDF and DMD were measured every 10–12 days. In spring, NDF increased from 503 to 604 g kg^?1, DMD decreased from 684 to 558 g kg^?1 and AFM increased from 0·64 to 2·82 t DM ha^?1. In autumn, NDF decreased from 543 to 442 g kg^?1, DMD increased from 591 to 681 g kg^?1 and AFM increased from 0·35 to 1·10 t DM ha^?1. The results show that the nutritive value of tall fescue through the year is not related to the accumulation of dry matter of the sward. Nutritive value is determined by the reproductive stage in late spring and early summer, the fate of photosynthates at different times of the year and the synthesis of non‐digestible compounds.     

Orchardgrass response to different types,rates and application patterns of dairy manure

Manure management is a difficult task on many intensive dairy farms. Crops that can utilize large quantities of manure N, yield quality forage with larger rates of manure application, and allow manure spreading at different times in a year can simplify that task. A study was conducted in 1990 and 1991 on a Copake sandy loam soil (mixed mesic) in New Milford, Connecticut. The objectives were: (1) to measure and compare dry matter (DM) response of orchardgrass (Dactylis glomerata L.) to different amounts and application times of N fertilizer and liquid and solid cattle manure; and (2) to determine crop uptake of fertilizer and manure N. Fertilizer and liquid and solid manure were applied to the soil surface annually in amounts of 150, 300 or 450 kg N ha⁻¹ in one, two or four equal applications. Orchardgrass dry matter production increased over the entire range of N amounts from all sources. Yields varied from approximately 2500 kg DM ha⁻¹ for control plots (0 kg N) to 10600 kg for plots receiving 450 kg N ha⁻¹ either as fertilizer or liquid manure. Crop response to liquid manure application was greater in year one with abundant rainfall than in year two with dry conditions during most of the growing season, whereas crop response to solid manure application improved in the second year, due to the availability of residual organic N. Orchardgrass was more sensitive to the timing of fertilizer N application than to manure N application. Despite the large differences in weather patterns experienced during this study, analysis of application patterns indicated that manure could be applied throughout the growing season to crop stubble (post-harvest) with comparable rates of uptake overall. N uptake in control plots averaged 56 kg N ha⁻¹ for both years, compared to 340 kg N ha ⁻¹ for fertilizer plots, 250 kg N ha ⁻¹ for liquid manure plots and 190 kg N ha⁻¹ for solid manure plots receiving 450 kg total N ha ⁻¹.     

Herbage and nitrogen yields,fixation and transfer by white clover to companion grasses in grazed swards under different rates of nitrogen fertilization

In grass–legume swards, biologically fixed nitrogen (N) from the legume can support the N requirements of the grass, but legume N fixation is suppressed by additional fertilizer N application. This study sought to identify a fertilizer N application rate that maximizes herbage and N yields, N fixation and apparent N transfer from white clover to companion grasses under intensive grazing at a site with high soil‐N status. During a 3‐year period (2011–2013), swards of perennial ryegrass and of perennial ryegrass–white clover, receiving up to 240 kg N ha^?1 year^?1, were compared using isotope dilution and N‐difference methods. The presence of white clover increased herbage and N yields by 12–44% and 26–72%, respectively. Applications of N fertilizer reduced sward white clover content, but the effect was less at below 120 kg N ha^?1. The proportion of N derived from the atmospheric N fixation was 25–70%. Nitrogen fixation ranged from 25 to 142 kg N ha^?1 measured using the isotope dilution method in 2012 and from 52 to 291 kg N ha^?1 using the N‐difference method across all years. Fertilizer N application reduced the percentage and yield of fixed N. Transfer of N from white clover to grass was not confirmed, but there was an increased N content in grass and soil‐N levels. Under intensive grazing, the maximum applied N rate that optimized herbage and N yields with minimal effect on white clover content and fixation rates was 60–120 kg N ha^?1.     

Successive annual applications of organic manures for cut grass: short-term observations on utilization of manure nitrogen

Abstract The recovery of nitrogen (N) from, and the fertilizer‐N value of, low dry‐matter (DM) cattle slurry and farm yard manure (FYM), applied annually to perennial ryegrass swards grown at two sites, on sandy loam and shallow calcareous silty clay loam soils, were studied over a 4‐year period. Slurry or FYM, applied at target rates of either 150 kg N ha^?1 or 300 kg N ha^?1 in either October, February or May/June, in combination with 150 kg N ha^?1 inorganic fertilizer‐N (applied as split dressings before the first and second grass cut), were compared with a set of inorganic fertilizer‐N response treatments. DM yield, N offtake, apparent manure‐N recovery (in herbage) and manure‐N efficiency (compared with inorganic fertilizer‐N) were determined at two silage cuts each summer. Soil mineral nitrogen (SMN) measurements in autumn and spring were used to assess potential N leaching loss over winter and to quantify available N residues in the soil in spring. Apparent manure‐N recovery and manure‐N efficiency were usually greater from slurry applications in February than from those in October, but the timing of the application of FYM had a much smaller effect, compared with the timings of the application of slurry, on the utilization of N from manure by grass. Spring assessment of SMN was useful in quantifying available N residues from October slurry applications. Manure‐N recovery for all application timings was, on average, higher from the sandy loam than the shallow calcareous clay loam. The application of slurry to grass in early spring, at a rate of 150 kg total N ha^?1, with the addition of a supplementary 50 kg inorganic fertilizer‐N ha^?1, was the most suitable strategy for utilizing slurry‐N effectively and for supplying the N requirement for first‐cut silage.     

Effect of fertilizer nitrogen source and cattle slurry on herbage production and nitrogen utilization

A field plot experiment was carried out on an established grassland sward from 1983–88 inclusive to examine the effects of time of application, chemical form of nitrogen (N) and cattle slurry dry matter (DM) content on yield and efficiency of N use. Four forms of fertilizer N (a semi-organic fertilizer, a combined 2.1:1 (w/w) semi-organic/calcium ammonium nitrate (CAN) fertilizer, CAN and urea, each supplying 300 kg N ha^?1 year^?1, were applied with or without unseparated or separated cattle slurry at 93 and 73 g kg^?1 DM respectively, both supplying approximately 150 kg N ha^?1 year^?1. All fertilizers and slurries were applied in three equal dressings (February/March, May/June and July/August). The efficiency of use of fertilizer and slurry N was evaluated by measuring DM yield, N uptake and apparent recovery of N in herbage at all harvests during each growing season. Fertilizer N application significantly increased (P<0.001) the mean yields of herbage at each harvest in all years. The form of fertilizer N had no significant effect (P>0.05) on first harvest and total herbage yields, nor on N uptakes by herbage at the first harvest in any year. The performance of urea and of CAN was more variable at the second and third harvests relative to that of the semi-organic or combined 2.2:1 (w/w) semi-organic/CAN sources which had similar efficiencies of N use. Lower DM production was associated with reduced uptake of N. Values for mean overall apparent recovery of N ranged from 57.9 ± 2.67% for the semi-organic fertilizer to 50.2±3.05% for CAN. Unseparated cattle slurry and separated cattle slurry produced similar herbage yields and N responses that were lower and more variable than with fertilizer N. The overall mean apparent recovery of N from unseparated cattle slurry was 25.5 ± 5.03% compared to 5.0 ± 4.74% for separated cattle slurry. Efficiency of N use was highest with spring applications and least with mid-season applications. Recoveries ranged from ?29% for separated cattle slurry applied in June 1984 to 56% for unseparated and separated cattle slurry applied in February 1988 and June 1987 respectively. No interactions were recorded between cattle slurry and fertilizer N in terms of DM production or N uptake by herbage. The results of this study support the use of a fertilizer N source, selected on a least-cost basis, in combination with slurry to promote spring herbage production. For subsequent production, N should be supplied in fertilizer form only. The use of urea is risky under low rainfall conditions. Mechanical separation did not improve the efficiency of use of slurry N.     

Effects of different levels of fertilizer application to veld on growth of steers and chemical composition of the herbage

The effects of different levels of N fertilization (no N, 40 kg N and 80 kg N ha^?1 year^?1), P fertilization (no P, 21 kg P ha^?1 year^?1 and 21 kg P plus 53 kg K ha^?1 year^?1) and stocking rates (0·52 large stock units (LSU) ha^?1, 0·78 LSU ha^?1 and 1·56 LSU ha^?1) on the chemical composition and in vitro dry matter digestibility of the herbage and the liveweight gains of steers were determined in the western variant of the Bankenveld in South Africa. The average daily liveweight gains (ADLGs) of the steers increased with increasing level of N fertilization. Fertilization with P had a positive effect on ADLG only when 53 kg of K was applied with 21 kg of P ha^?1. Higher stocking rates reduced ADLGs. The liveweight gains ha^?1 increased as the rates of N and P fertilization increased. The medium stocking rate (0·78 LSU ha^?1) gave a higher liveweight gain ha^?1 than the lowest stocking rate (0·52 LSU ha^?1), but the highest stocking rate (1·56 LSU ha^?1) reduced liveweight gain ha^?1. In general, in terms of chemical components, a higher nutritive value of the veld herbage resulted from N fertilization. The higher crude protein (CP) content of the herbage, resulting from higher stocking rates, should be seen against the background of lower liveweight gains ha^?1 at the highest stocking rate. On pasture with similar contents of CP and acid detergent fibre (ADF), higher ADLG of steers was found as a result of P and K fertilization, especially for herbage with a lower CP and a higher ADF content, implying better utilization of the nutrients in such herbage with P and K fertilization, although P was also supplemented through a lick.     

Effects of sowing date and nitrogen fertilizer on forage yield,nitrogen‐ and water‐use efficiency and nutritive value of an annual triple‐crop complementary forage rotation

Complementary forage rotation (CFR) systems based on non‐limiting inputs of fertilizer nitrogen (N) (～600 kg N ha^?1) are perceived as uneconomic. An experiment was carried out in Australia to investigate the effects of rates and timing of N fertilizer and sowing date on yield, nutrient‐use efficiency and nutritive value of a triple‐crop (maize, forage rape, field peas) CFR system. Treatments were early‐ and late‐sown maize grown with 0 or 135 kg fertilizer N ha^?1 pre‐sowing (N1) and 0, 79 or 158 kg N ha^?1 post‐sowing (N2). Forage rape was sown with 0 or 230 kg N ha^?1 (N3) and field peas without N. Application of fertilizer N at N1, N2 and N3 increased CFR yield from 28·5 to 48·8 t dry matter (DM) ha^?1 and irrigation water‐use efficiency (IWUE) from 3·4 to 6·1 t DM per megalitre. Increase in yield and IWUE of CFR occurs at the expense of nitrogen‐use efficiency (NUE) as applications of N at N1, N2 and N3 decreased NUE of CFR from 524 to 91 kg DM kg^?1 N. Nutritive value, particularly metabolizable energy content of all forages, was similar among N treatments, and interactions between treatments were minimal. Results indicate that increase in NUE of CFR may occur at the expense of reduced yield, but increased IWUE need not compromise the yield of this CFR system.