Methyl bromide soil fumigation: Effect on grass yields

Annual herbage yields of grasses grown on sandy soils on Henderson Research Station seldom exccecîf 10 000 kg/ha dry matter, while on heavy clay soils yields of 18 000 kg/ha are consistently obtained with similar amounts of applied fertilizers.

Eight grass species were established in sandy soil that had either not been fumigated or been fumigated with methyl bromide against soil nematodes. In the following season herbage dry matter yields increased from 13 280 kg/ha to 15 690 kg/ha due to fumigation, ou the average, while increases of 50% or more were obtained for three grasses. Yield reductions in two species may have been due to phytoloxic residues.

Fumigation reduced the number of nematodes in the soil and in the grass roots.     

Effects of eight grazing systems on carcass mass gains of steers grazing irrigated Cynodon aethiopicus pastures

Abstract

Eight grazing systems were compared on irrigated Cynodon aethiopicus pastures which received 650 kg N, 36 kg P and 200 kg dolomitic limestone/ha, annually. There were either one, two, three, six or 18 paddocks in the systems, the single paddock system being continuously grazed. The others were rotational systems with various periods of grazing and of resting.

Using the comparative slaughter technique carcass mass gains of crossbred Hereford/Afrikaner steers were calculated. Three‐year mean carcass mass gains over stocking rates from 12 to 18 steers/ha ranged from 872 to 997 kg/ha. None of the rotational systems were better than continuous grazing.

Estimates of amounts of herbage available for grazing in each system showed that there was least in the continuous grazed and most in the multi‐paddock systems where there were long periods of rest between successive grazing.     

Pasture management effects on diet composition and cattle performance on continuously stocked rhizoma peanut-mixed grass swards

In Florida, rhizoma peanut (RP; Arachis glabrata Benth.), a tropical legume, combines the attributes of excellent nutritive value, competitive ability with tropical grasses, and high animal performance. The objective of this study was to determine the effects of spring N fertilization (0 vs 35 kg/ha) and summer stocking rate (1.5 and 2.5 bulls/ha) on herbage mass, nutritive value, herbage allowance, and diet botanical composition of grazed RP-grass swards and their interaction with growth and development of bulls (Senepol, and Brahman or Angus). The study was conducted in 1995 and 1996 at the USDA, ARS, Subtropical Agriculture Research Station in Brooksville, FL. Nitrogen was applied in April of each year, and all pastures were stocked with 1.5 bulls/ha until approximately July of each year, when stocking rate was increased on half the pastures to 2.5 bulls/ha. Herbage mass (HM, kg/ha), herbage allowance (HA, kg/kg BW), nutritive value (CP and in vitro organic matter digestibility [IVOMD]), and diet botanical composition (fecal microhistological) readings were determined. Animal measurements included total and seasonal (spring vs summer), ADG, hip height (cm), scrotal circumference (SC, cm), and plasma urea nitrogen (PUN, mg/dL). Herbage mass (3.0 +/- 0.12 Mg/ha and 3.4 +/- 0.13 Mg/ha in 1995 and 1996, respectively) was not affected by nitrogen fertilization or stocking rate but was affected by season (P < 0.05) due to increased plant growth rate associated with summer rainfall. Stocking rate did affect herbage availability, but it never fell below 3 kg/kg BW, indicating herbage availability was never limiting. Crude protein (200 to 140 g/kg) and IVOMD (650 to 540 g/kg) were not affected by treatment, but declined (P < 0.001) from spring until fall. Treatments also had no effect on diet botanical composition. Summer ADG averaged about 0.2 kg/d lower than spring ADG, due, in part, to seasonal declines in nutritive value. Because herbage allowance was never limiting, full-season ADG was not affected by stocking rate or N fertilization and averaged 0.61 +/- 0.03 and 0.60 +/- 0.02 kg/d in 1995 and 1996, respectively. There were season x breed interactions (P < 0.05) for ADG due to greater declines during the summer for Angus than for Senepol or Brahman. There were no differences in final BW, SC, BCS, hip height, or PUN due to treatments, but breed differences were noted (P < 0.05) for all measures except BCS.     

Effect of nitrogen concentration of urea ammonium nitrate,and application level,on the dry matter and chemical composition of Pennisetum clandestinum and Cynodon hybrid dryland pastures

Liaraquid urea ammonium nitrate (UAN) was applied to dryland Pennisetum clandestinum (Kikuyu (Chiov)) and Cynodon hybrid (Coastcross II (L.) (Pers.)) pastures at two levels (207 and 414 kg N/ha/season) and at three concentrations (10,5; 21 and 42% N) of nitrogen. The degree of leaf scorch increased as both the amount of N and the concentration of UAN increased, but persisted in all treatment combinations for between 10 and 14 days only. Scorch did not appear to materially affect yields measured six weeks after UAN application. Significant interactive effects were evident between the quantity of N applied and UAN concentration in estimates of yield and many of the quality factors. In general, however, herbage yield declined with increasing N concentration in the UAN at the low N (207 kg N/ha) level, but was highest at the 21% N concentration when the amount of N applied was twice this level (414 kg N/ha). Herbage N, K, Ca and Mg content generally declined as N concentration in the UAN increased, but P levels responded positively to increased UAN concentration. UAN appeared to be most effective as a nitrogen carrier when it was diluted two to four‐fold.     

Establishment of stylosanthes guyanensis in marandellas sandveld

The feasibility of establishing perennial forage legumes in veld has been investigated at Grasslands Research Station, Marandellas. Of the species tested, Stylosanthes guyanensis (stylo) appeared most suitable.

Reduction of competition from veld grasses was essential for satisfactory establishment of the legume; this was best achieved by shallow discing which also produced a suitable seedbed.

The density of stylo seedlings was affected by seeding rate and degree of soil preparation. More plants established from 4,5 kg/ha of seed broadcast onto disced soil than from 18,0 kg/ha sown onto undisturbed ground. Periodic grazing during the season of establishment had no effect on seedling density. Herbage yields followed the same trends as stylo density. Yields from the plots with the greatest density of stylo plants were more than twice those from the plots with the lowest density.

Seeding stylo into disced veld raised dry matter yields 50% and crude protein yields 300%, although yields of grass were reduced by the addition of the legume. Annual applications of 112 kg superphosphate/ ha had no effect on yields.     

The effect of form and level of nitrogen fertlization on the yield of Digitaria eriantha Steud*

Abstract

On dryland Digitaria eriantha ammonium sulphate and limestone ammonium nitrate were superior to potassium nitrate and urea. With reference to the level of nitrogen fertilization it was found that levels in excess of 300 kg N/ha, and up to 400 kg N/ha, could be economically justified, even on a pasture with a high basal level of fertility.     

Band placement of lime and superphosphate for ladino clover in an acid oxysol

In a pot experiment with the A₁ (topsoil) and B₂ (subsoil) horizons of a Clovelly soil, it was found that although increasing the rate of band‐placed lime from 265 to 2650 kg per ha did not significantly influence the yield of Ladino clover, considerably higher yields were obtained where the pH of the entire soil mass was raised from approximately pH 5.0 to 6.0 by liming.

It is suggested that Al‐toxicity is a major limiting factor in this soil and may largely account for the response to liming. Increasing the band‐placed superphosphate application from 265 to 2650 kg per ha resulted in highly significant yield increases. Considerable root development occurred in the superphosphate bands as compared with limited root development in the lime bands. Significantly higher yields were obtained from the A₁ horizon than from the B₂ horizon. Differences due to depth of placement of the lime and superphosphate, placement of the lime and superphosphate in a single band as opposed to separate parallel bands, and the use of powdered and granular superphosphate were recorded in the first cut but not in the second.     

Steers performance in dwarf elephant grass pastures alone or mixed with Arachis pintoi

The inclusion of legumes in pasture reduces the need for mineral nitrogen applications and the pollution of groundwater; however, the agronomic and animal husbandry advantages with tropical legumes are still little known. The objective of this study was to quantify the effect of the use of forage peanut (Arachis pintoi cv. Amarillo) in dwarf elephant grass pastures (Pennisetum purpureum cv. BRS Kurumi) on forage intake and animal performance. The experimental treatments were dwarf elephant grass fertilized with 200 kg?N/ha, and dwarf elephant grass mixed with forage peanut without mineral fertilizers. The animals used for the experiment were 12 Charolais steers (body weight (BW)?=?288?±?5.2 kg) divided into four lots (two per treatment). Pastures were managed under intermittent stocking with an herbage allowance of 5.4 kg dry matter of green leaves/100 kg BW. Dry matter intake (mean?=?2.44 % BW), the average daily gain (mean?=?0.76 kg), and the stocking rate (mean?=?3.8 AU/ha) were similar between the studied pastures, but decreased drastically in last grazing cycle with the same herbage allowance. The presence of peanut in dwarf elephant grass pastures was enough to sustain the stocking rate, but did not allow increasing forage intake and animal performance.     

“麦/玉/豆”模式下氮肥运筹对玉米碳氮代谢的影响

在“麦/玉/豆”套作模式下,以玉米杂交种川单418为材料,采用两因素随机区组设计,通过2年试验研究了不同施氮量0,90,180,270,360 kg纯N/hm²,和不同施氮时期即底肥∶拔节肥∶攻苞肥=5∶0∶5,3∶2∶5和5∶2∶3对玉米碳氮代谢的影响。研究结果表明,施氮量低于270 kg纯N/hm²时,随着施氮量的增加,玉米叶片、茎鞘的氮素和总糖积累以及碳氮代谢关键酶硝酸还原酶、谷氨酰胺合成酶、蔗糖磷酸合成酶活性表现出增加趋势,超过270 kg纯N/hm²时会起抑制作用,2年均以施氮量为270 kg纯N/hm²时表现最优,其次是施氮量为180 kg纯N/hm²,施氮量为180和270 kg纯N/hm²时显著或极显著高于对照。各施氮处理叶片C/N从拔节期至乳熟期平均下降速率分别为26%,25%,21%,23%,且当施氮量为270 kg纯N/hm²时茎鞘C/N保持较低水平,叶片乳熟期仍然保持高效合成能力,有利于产量形成。不同氮肥配比对碳氮代谢影响表现为3∶2∶5>5∶0∶5>5∶2∶3,氮肥后移(3∶2∶5)促进叶片和茎鞘糖、氮积累,增强硝酸还原酶、谷氨酰胺合成酶和蔗糖磷酸合成酶活性,与氮肥前移(5∶2∶3)相比差异显著。因此“麦/玉/豆”模式结合氮肥运筹能够协调并能明显改善玉米碳氮代谢,进而实现周年作物的可持续生产。综合总糖、氮素的积累以及碳氮代谢关键酶的表现,“麦/玉/豆”模式下以施270 kg纯N/hm²,基追比3∶2∶5为最佳氮肥运筹方式。     

The influence of nitrate and ammonium forms of nitrogen fertilizer on the growth and osmoregulation of digitaria eriantha and Chloris gayana grown under saline conditions

Abstract

Digltaria eriantha and Chloris gayana were grown under controlled conditions for three months and were treated with a nutrient solution containing 150 mMol NaCl and the following nitrogen sources: 25 or 200 mg/l NH₄ ⁺‐N or NO₃ ^?‐N or no nitrogen. The application of nitrogen was found to stimulate growth, i.e. leaf area and dry mass in both grasses, with a greatest growth response to both NH₄ ⁺—N treatments in D. eriantha, and NH₄ ⁺‐N and NO₃ ^?—N treatments in C. gayana. Proline accumulated in both grasses, but this accumulation followed different trends in the two grasses. Soluble sugars (non‐structural) accumulated in the above ground component in D. eriantha, while in C. gayana soluble sugars accumulated predominantly in the roots, possibly as osmotica, or for storage and may thus have been available for regrowth.     

Suppression of Cheatgrass by Perennial Bunchgrasses

Long-term control of the invasive annual grass cheatgrass is predicated on its biological suppression. Perennial grasses vary in their suppressive ability. We compared the ability of a non-native grass (“Hycrest” crested wheatgrass) and two native grasses (Snake River wheatgrass and bluebunch wheatgrass) to suppress cheatgrass. In a greenhouse in separate tubs, 5 replicates of each perennial grass were established for 96 d, on which two seeds of cheatgrass, 15 cm apart, were then sown in a semicircular pattern at distances of 10 cm, 30 cm, and 80 cm from the established perennial bunchgrasses. Water was not limiting. After 60 d growth, cheatgrass plants were harvested, dried, weight recorded, and tissue C and N quantified. Soil N availability was quantified at each location where cheatgrass was sown, both before sowing and after harvest. Relative to cheatgrass grown at 80 cm, all perennial grasses significantly reduced aboveground biomass at 30 cm (68% average reduction) and at 10 cm (98% average reduction). Sown at 10 cm from established perennial grasses, cheatgrass aboveground biomass was inversely related with perennial grass root mass per unit volume of soil. All cheatgrass sown at 10 cm from “Hycrest” crested wheatgrass died within 38 d. Before sowing of cheatgrass, soil 10 cm from established perennial grasses had significantly less mineral N than soil taken at 30 cm and 80 cm. Relative to cheatgrass tissue N for plants grown at 80 cm, cheatgrass nearest to the established perennial grasses contained significantly less tissue N. All perennial grasses inhibited the NO₂⁻ to NO₃⁻ nitrification step; for “Hycrest” crested wheatgrass, soil taken at 10 cm from the plant had a molar proportion of NO₂⁻ in the NO₂⁻ + NO₃⁻ pool of > 90%. In summary, a combination of reduced nitrogen availability, occupation of soil space by perennial roots, and attenuation of the nitrogen cycle all contributed to suppression of cheatgrass.     

Influence of stocking rate and grazing systems on available grazing in the northern cape 1

Abstract

The influence of rotational and continuous grazing systems, each applied with four stocking rates, on the above‐ground phytomass of veld was determined over four years.

Grazing systems showed a significant influence on available herbage during one year only. Increased stocking rates brought a progressive decline in above‐ground phytomass. During the fourth season (1980/81) the average grazing pressures at stocking rates of 10 ha, 7 ha, 5,5 ha and 4 ha/Large stock unit were 5 984 kg, 3 417 kg, 2 390 kg and 1 238 kg and 1 238 kg phytomass/Large stock unit, respectively. At the end of the fourth season (July, 1981) there was reserve grazing available on the various stocking rates for approximately 579 days, 337 days, 202 days and 76 days, respectively. The risk of high stocking rates in the marginal rainfall regions, is emphasised.     

Effect of the type of silage on milk yield,intake and rumen metabolism of dairy cows grazing swards with low herbage mass

The aim of this study was to evaluate the effect of herbage allowance (HA) and type of silage supplemented (TS) on milk yield, dry matter intake (DMI) and metabolism of dairy cows in early lactation. Thirty‐six Holstein‐Friesian dairy cows were allocated to four treatments derived from an arrangement of two HA (LHA = 17 or HHA = 25 kg of DM/cow/day) and two TS (grass (GS) or maize (MS)). Herbage allowance had no effect on DMI or milk yield. Rumen pH and NH₃‐N concentration were not affected by HA. The efficiency of microbial protein synthesis in the rumen (microbial protein (MP)) was affected by HA with 21.5 and 23.9 g microbial nitrogen per kg ruminal digestible organic matter for LHA and HHA, respectively (P < 0.05). Supplementation with MS showed higher values of milk yield by 2.4 kg/cow/day (P < 0.001), milk protein content by 0.10 % (P < 0.023) and herbage DMI by 2.2 kg/cow/day, and showed lower values for milk urea compared to GS (P < 0.001). The former results suggest that TS had a greater effect on milk yield, total feed intake and energy intake than increase in herbage allowance; however, increase in HA had greater effects on MP than TS.     

Influences of nitrogen fertilization and energy supplementation for growth perfomance of beef cattle on Alexander grass

This study evaluated the influences of nitrogen fertilizer and energy supplementation cattle on the growth performance of beef cattle. This study was conducted at the Federal University of Technology of Paraná, Dois Vizinhos through continuous grazing on 6.3 ha, divided into nine paddocks. The treatments were: Alexander grass +100 kg ha^?1 of N (N100); Alexander grass + 100 kg ha^?1 of N + 0.5 kg per 100 kg of weight live supplementation of wheat bran (N100S); and Alexander grass +200 kg ha^?1 of N (N200), with an average herbage allowance of 10% for all treatments. Crossbred and non-castrated steers with an average weight of 276 ± 41 kg were used for 107 days. The crude protein from entire plant differed (P < 0.05) between treatments, with the greater value (14.8%) occurring in the N200, and the lesser value (13.3%) occurring in the N100S. The herbage accumulation rate was greater (P < 0.05) in the N200 (55.7  DM ha^?1 d^?1) than that in the N100S and N100 (40.0 and 39.7 kg DM ha^?1 d^?1, respectively). The N100S produced greater (P < 0.05) average daily weight gains (0.815 kg animal day^?1) than did the N200 (0.685 kg animal day^?1) and N100 treatments (0.727 kg animal day^?1).

     

不同生境苦豆子种群的生产性能

本研究重点比较了干旱和湿润生境下,苦豆子(Sophora alopecuroides)的草产量、种子产量、种子大小和种子硬实率等生产性能的指标和特性。在广泛分布地区选择5个测定地点,包括甘肃临泽、民勤,宁夏盐池,内蒙古阿拉善左旗和额济纳旗。结果表明,生长环境对苦豆子的生产性能影响很大;干旱生境的每分枝干草产量均小于湿润生境的,分别为4.9和7.2g,干旱生境与湿润生境单位面积的干草产量分别为1 330.7和1 546.1kg·hm~(-2);各地点单位面积与每分枝的种子产量、收获指数、硬实率和千粒重,均表现为干旱生境高于湿润生境,其中,干旱生境的平均实际种子产量和收获指数均显著高于湿润生境的(P0.05),分别为335.0kg·hm~(-2)、1.2g·分枝-1和17.0%,是湿润生境的2.2、1.7和2.1倍;干旱生境的平均硬实率为91.0%,高于湿润生境5.7个百分点;干旱生境种子平均千粒重为19.5g,是湿润生境的1.3倍。两种生境的生殖枝密度和每荚果种子数均与单位面积种子产量呈极显著正相关(P0.01)。依据本研究数据估测,我国苦豆子的干草总产量和种子产量分别为239.5万~278.3万t和27.8万~60.3万t。     

Impact of grazing intensity on herbage intake, composition, and digestibility and on live weight gain of sheep on the Inner Mongolian steppe

High grazing pressure during the last decades caused severe ecological problems in the steppe of Inner Mongolia, China. The objective of the present study was to determine the effects of grazing intensity of sheep on herbage mass (HM) and intake, chemical composition and digestibility of herbage, and on live weight gain (LWG). A grazing experiment with six different grazing intensities (1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 sheep/ha) was conducted in the growing season of 2005 in the Xilin River Basin. HM decreased from 1.5 t DM/ha at the lowest grazing intensity to 0.6 t DM/ha at the highest grazing intensity. NDF content of the herbage was high (> 700 g/kg DM) and relatively constant, whereas acid detergent lignin (ADL) content increased with grazing intensity and with proceeding grazing season. Digestibility of organic matter ingested (DOM) tended to decrease with grazing intensity as well as intake of organic matter (OMI) and of digestible organic matter (DOMI) per sheep (P = 0.090 and P = 0.065, respectively), whereas LWG per sheep decreased with increasing grazing intensity (P = 0.018). DOM and OMI were negatively related to ADL content. However, herbage intake and LWG per ha increased with grazing intensity (P < 0.001) and reached their maximum at 9 and 7.5 sheep per ha, respectively. This observation confirms the current farmers' practise of high grazing pressure ignoring long term grassland productivity and ecological problems. Therefore, the studies are continued to provide further information on long term effects. This study could show pronounced effects of grazing intensity on animal and grassland productivity and the suitability of the methods applied to measure intake and digestibility of herbage in a large scale grazing experiment with sheep.     

Identification of companion legumes for midmar Italian ryegrass

Abstract

In a preliminary investigation seven legumes were planted alone and in combination with Lolium multiflorum cv. Midmar. The pure stands of legumes were harvested at either four, five or six week cutting intervals, while the pure stands of Lolium multiflorum and the ryegrass/legume mixtures received in addition to the cutting treatments 0, 200 or 400 kg N/ha in four equal applications. The ryegrass and legume components were harvested separately for dry matter yield (DM) and crude protein (CP) determinations.

Trifolium repens and T. pratense were the most suited companion legumes in terms of DM yield, CP content and the ability to extend the growing season. Ornithopus sativus and T. vesiculosum were the most suited annual legumes to grow in combination with L. multiflorum. Nitrogen had a far stronger positive effect on the DM yields and CP content than cutting interval, with the pure stands of L. multiflorum responding the most to nitrogen. The legume DM yields were adversely affected by the addition of nitrogen and by lengthening of the cutting interval. The incorporation of legumes into a ryegrass sward had the greatest positive effect on DM yields and CP content and yield when no nitrogen was applied and when harvested at six week intervals. Dry matter yields of the mixtures were only slightly reduced when half the maximum amount of nitrogen was applied.     

刈割高度与施氮量对饲料桑全株产量及营养品质的影响

本研究以饲料桑新品种‘川饲桑1号’（Morus alba cv. Chuansisang-1）为试验材料,采用二因素随机区组设计连续3年（2016-2018）对不同刈割高度（H₁：70 cm,H₂：90 cm,H₃：110 cm）和施氮量（N₁：138 kg N·hm^-2,N₂：207 kg N·hm^-2,N₃：276 kg N·hm^-2）下的饲草产量、植物学特性及营养品质进行测定,并对其饲用价值进行综合评价,以期为饲料桑的推广利用提供数据支撑。结果表明,随着年限的增加各处理下饲草产量逐年递增,且均以H₂N₃处理最高。刈割高度与施氮量对饲料桑产量、植物学特性和营养品质均有影响。其中,刈割高度是影响饲料桑植物学特性的主要因素,两者交互作用对饲草产量、单枝重及各营养指标影响显著（P<0.05）。在相同刈割高度下,鲜、干草产量和中性洗涤纤维均以N₃处理最高,粗蛋白含量随施氮量的增加先增加后减小。在相同氮肥用量下,H₂处理下的大部分饲草产量、主枝叶片数、单株重最大,中性洗涤纤维和酸性洗涤纤维含量整体随刈割高度的增加而增大。粗蛋白和粗灰分含量整体在H₂高度下最高,粗脂肪含量随刈割高度增加呈先升高后降低的趋势。以隶属函数法对‘川饲桑1号’的饲用价值进行综合评价可知,在刈割高度为90 cm、施氮量为276 kg N·hm^-2时其饲用价值最高。     

Production and quality norms of certain grass species for fodder flow planning: Pretoria area

Abstract

Four subtropical (Cenchrus. Digitaria, Anthephora and Sorghum) and two temperate grass species (Festuca. Agrotricum) were grown in a replicated field experiment at three levels of N application, with adequate P and K. Species were mown at 4‐, 6‐ and 8‐weekly intervals. DM production data for 6‐ and 8‐weekly and 4‐ and 6‐weekly intervals are presented for subtropicals and temperates, respectively.

The object was to determine the seasonal accumulative DM production curves, productivity spread and quality, for use in fodder flow planning.

The subtropical grasses produced 2 to 3 times as much DM as the temperate grasses : CGR 745—1237 versus 345—440 kg/ha/wk under supplementary irrigation. The subtropicals produced ca 2^{h times as much under irrigation than under rainfed conditions.

Festuca and Agrotricum, Digitaria. Athephora and Sorghum, Cenchrus, gave peak CGR's after 9, 15, 16 and 18 weeks after end of August, respectively. Irrigation resulted in peak CGR being reached earlier in the growing season than under rainfed conditions and in subtropicals maintaining a high CGR for 1½ — 2½ months longer.

Various implications of the results for pasture management, and the fact that quality and DM yield generally are antagonistic in subtropical grasses, were discussed.     

Influence of soil PH and fertilization on the dry matter production,chemical composition and digestibility of perennial grasses : II panicum maximum JACQ 1

Abstract

The reaction of Anthephora pubescens to N, P and K fertilization was evaluated from 1976 to 1983. Dry matter production at N levels of 0; 75 and 150 kg/ha were 1,9; 2,2 and 2,3 ton/ha respectively. This relative poor reaction to N was related to rainfall variations and the initial low soil P status. A significant N × P interaction was recorded. Dry matter production increased from 1,6 ton/ha at the NO × PO treatment to 2,8 ton/ha at the 150 kg N/ha × 20 kg P/ha treatment. Anthephora responded poorly to K fertilization and the mean dry matter production was 2,1; 2,2 and 2,2 ton/ha with 0; 75 and 150 kg K/ha respectively.

The mean crude protein content of A. pubescens increased from 6,5 % at the NO level to 8,8 % with 150 kg N/ha. The P content of plant material increased from 0,13 % at the PO level to 0,20 % with 20 kg P/ha. The Zn content of plant material dropped to sub‐optimal levels during the trial.