Efficiency of rice fertilization schedules including cyanobacteria under soil application of phosphate and molybdate

Productive tillering, grain and straw yields and N-contents of indica rice IR-28 were increased more by urea fertilizer at 48 or 96 kg N/ha along with Inoculation by cyanobacteria than by using 144 kg N/ha without inoculation. Fertilizer N-use efficiency was increased by the cyanobacteria and decreased with increasing amount of urea fertilizer. Further enhancement was obtained by soil application of calclum superphosphate at 36 kg P₂O₅/ha or sodium molybdate at 1 ppm Mo along with cyanobacteria and/or urea. Application of phosphate, however, slightly diminished the enhancement by molybdate.The author is with the Sakha Agricultural Research Station, Kafr El-Sheikh, Egypt.     

Efficiency of algalization of rice in the Nile Delta with different amounts of nitrogen and potassium fertilization

Indica rice var. IR 28 was inoculated with cyanobacteria (blue-green algae) together with elther 0,72 and 144 kg N/ha or 0,60 and 120 kg K₂O/ha. Plant performance, yield, nitrogen contents and chemical fertilizer-N-use efficiency positively responded to inoculation with the cyanobacteria and increased further with increasing amounts of both N and K. Effects arising from the cyanobacteria, N or K differed under the other two factors.     

Methane production in rice soil is inhibited by cyanobacteria

The present study was aimed at understanding the role of cyanobacteria and Azolla in methane production and oxidation in laboratory simulation experiments using soil samples from rice fields. All the seven cyanobacterial strains tested effected a significant decrease in the headspace concentration of methane in flooded soil, incubated under light. Synechocystis sp. was the most effective in retarding methane concentration by 10-20 fold over that in controls without cyanobacteria. The decrease in the headspace concentration of methane was negligible in nonsterile soil samples, inoculated with Synechocystis sp. and then incubated under dark. Moist soil cores (0-5 cm depth), collected from rice fields that had been treated with urea in combination with a cyanobacterial mixture, Azolla microphylla, or cyanobacterial mixture plus A. microphylla, effected distinctly more rapid decrease in the headspace concentration of methane added at 200 microl(-1) than did the soil cores from plots treated with urea alone (30, 60, 90 and 120 kg N ha(-1)), irrespective of the rate of chemical nitrogen applied to rice fields. Besides, soil cores from plots treated with urea alone at 60, 90 and 120 kg N ha(-1) oxidised methane more rapidly than did the core samples from plots treated with urea alone at 30kg N ha(-1). Cyanobacteria and A. microphylla, applied to flood water, appear to play a major role in mitigation of methane emission from rice fields-through enhanced methane oxidation.     

Evaluation of the availability ofAzolla-N and urea-N to rice using15N

Summary The symbiotic association of the water fernAzolla with the blue-green algaAnabaena azollae can fix 30–60 kg N ha^–1 per rice cropping season. The value of this fixed N for rice production, however, is only realized once the N is released from theAzolla biomass and taken up by the rice plants. The availability of N applied asAzolla or as urea was measured in field experiments by two¹⁵N methods. In the first,Azolla caroliniana (Willd.) was labelled with¹⁵N in nutrient solution and incorporated into the soil at a rate of 144 kg N ha^–1. The recovery ofAzolla-N in the above ground parts of rice [Oryza sativa (L) cv. Nucleoryza] was found to be 32% vs. 26% for urea applied at a rate of 100 kg N/ha; there was no significant difference in recovery. In the second, 100 kg N/ha of¹⁵N-urea was applied separately or in combination with either 250 or 330 kg N ha^–1 of unlabelledAzolla. At the higher rate, the recovery ofAzolla-N was significantly greater than that of urea. There was a significant interaction when both N sources were applied together, which resulted in a greater recovery of N from each source in comparison to that source applied separately. Increasing the combined urea andAzolla application rate from 350 kg N ha^–1 to 430 kg N ha^–1 increased the N yield but had no effect on the dry matter yield of rice plants. The additional N taken up at the higher level of N application accumulated to a greater extent in the straw compared to the panicles. Since no assumptions need to be made about the contribution of soil N in the method using¹⁵N-labelledAzolla, this method is preferable to the¹⁵N dilution technique for assessing the availability ofAzolla-N to rice. Pot trials usingAzolla stored at –20°C or following oven-drying showed that both treatments decreased the recovery of N by one third in comparison to freshAzolla.     

Role of algalization in rice growth,yield and incidence of infestation with the stem borerChilo agamemnon Bles. and the leaf minerHydrellia prosternalis Deeming in the Nile Delta

Blue-green algae as a soil-based inoculum was applied to short-duration Indica rice in combination with 72 kg N/ha and compared with just N fertilization applied as 144 kg N/ha. Fertilizer N was applied in two equal doses 25 days after transplanting and at mid-tillering stage. The algal inoculum, which containedAnabaena cylindrica, Anabaena oryzae, Nostoc muscorum andTolypothrix tenuis, was applied at 100 kg/ha fresh material (90% moisture) 5 days after transplanting. Five different combinations of microelements were sprayed as a foliar application simultaneously with fertilizer N. Plant performance was enhanced by inoculation with algae and microelements compared with complete N fertilization only. Natural infestation with the stem borer,Chilo agamemnon, and leaf miner,Hydrellia prosternalis, decreased significantly during growth and up to harvesting with application of algae, Endosulfan, and increased with application of microelements.     

Epiphytic cyanobacteria on Chara vulgaris are the main contributors to N(2) fixation in rice fields

The distribution of nitrogenase activity in the rice-soil system and the possible contribution of epiphytic cyanobacteria on rice plants and other macrophytes to this activity were studied in two locations in the rice fields of Valencia, Spain, in two consecutive crop seasons. The largest proportion of photodependent N(2) fixation was associated with the macrophyte Chara vulgaris in both years and at both locations. The nitrogen fixation rate associated with Chara always represented more than 45% of the global nitrogenase activity measured in the rice field. The estimated average N(2) fixation rate associated with Chara was 27.53 kg of N ha(-1) crop(-1). The mean estimated N(2) fixation rates for the other parts of the system for all sampling periods were as follows: soil, 4.07 kg of N ha(-1) crop(-1); submerged parts of rice plants, 3.93 kg of N ha(-1) crop(-1); and roots, 0.28 kg of N ha(-1) crop(-1). Micrographic studies revealed the presence of epiphytic cyanobacteria on the surface of Chara. Three-dimensional reconstructions by confocal scanning laser microscopy revealed no cyanobacterial cells inside the Chara structures. Quantification of epiphytic cyanobacteria by image analysis revealed that cyanobacteria were more abundant in nodes than in internodes (on average, cyanobacteria covered 8.4% +/- 4.4% and 6.2% +/- 5.0% of the surface area in the nodes and internodes, respectively). Epiphytic cyanobacteria were also quantified by using a fluorometer. This made it possible to discriminate which algal groups were the source of chlorophyll a. Chlorophyll a measurements confirmed that cyanobacteria were more abundant in nodes than in internodes (on average, the chlorophyll a concentrations were 17.2 +/- 28.0 and 4.0 +/- 3.8 microg mg [dry weight] of Chara(-1) in the nodes and internodes, respectively). These results indicate that this macrophyte, which is usually considered a weed in the context of rice cultivation, may help maintain soil N fertility in the rice field ecosystem.     

Contribution of N2 fixing cyanobacteria to rice production: availability of nitrogen from 15N-labelled cyanobacteria and ammonium sulphate to rice

This study investigate the potential contribution of nitrogen fixation by indigenous cyanobacteria to rice production in the rice fields of Valencia (Spain). N₂-fixing cyanobacteria abundance and N₂ fixation decreased with increasing amounts of fertilizers. Grain yield increased with increasing amounts of fertilizers up to 70 kg N ha^-1. No further increase was observed with 140 kg N ha^-1. Soil N was the main source of N for rice, only 8–14% of the total N incorporated by plants derived from ¹⁵N fertilizer. Recovery of applied ¹⁵N-ammonium sulphate by the soil–plant system was lower than 50%. Losses were attributed to ammonia volatilization, since only 0.3–1% of applied N was lost by denitrification. Recovery of ¹⁵N from labeled cyanobacteria by the soil–plant system was higher than that from chemical fertilizers. Cyanobacterial N was available to rice plant even at the tillering stage, 20 days after N application. This revised version was published online in June 2006 with corrections to the Cover Date.     

Response of irrigated dry-seeded rice to nitrogen and phosphorus in a semi-arid environment

Summary Under semi-arid conditions, three field experiments were conducted at Gezira Research Station to determine response of irrigated dry-seeded rice (Oryza sativa L. var IR 2053-206-1-3-6) to addition of nitrogen and phosphorus fertilizers. The experimental treatments included the factorial combinations of seven levels of nitrogen applied as urea and four levels of phosphorus applied as super phosphate. Plant growth and grain yield were significantly and progressively increased with the rise in the levels of added nitrogen and phosphorus. However, response to added phosphorus was restricted by the applied level of nitrogen. The responses of grain yield to nitrogen and phosphorus levels are given by quadratic regression equations. Without addition of nitrogen or phosphorus grain yield averaged 1.52 t/ha compared to 6.07 t/ha with addition of the optimal levels (160 kg N plus 35 kg P/ha). The high potential for rice production in semi-arid environment is evidently restricted by addition of relatively high rates of nitrogen and phosphorus.     

Effect of plant genotype and nitrogen fertilizer on symbiotic nitrogen fixation by soybean cultivars

Summary Isotopic as well as non-isotopic methods were used to assess symbiotic nitrogen fixation within eight soybean [Glycine max (L.) Merr.] cultivars grown at 20 and 100 kg N/ha levels of nitrogen fertilizer under field conditions.The¹⁵N methodology revealed large differences between soybean cultivars in their abilities to support nitrogen fixation. In almost all cases, the application of 100 kg N/ha resulted in lower N₂ fixed in soybean than at 20 kg N/ha in the first year of the study. However, N₂ fixed in one cultivar, Dunadja, was not significantly affected by the higher rate of N fertilizer application. These results were confirmed by measurements of acetylene reduction activity, nodule dry weight and N₂ fixed as measured by the difference method. Further proof of differences in N₂ fixed within soybean cultivars and the ability of Dunadja to fix similar amounts of N₂ at 20 and 100 kg N/ha was obtained during a second year experiment. Dunadja yield was affected by N fertilizer and produced larger yield at 100 kg N/ha than at 20 kg N/ha. This type of cultivar could be particularly useful in situations where soil N levels are high or where there is need to apply high amounts of N fertilizer.The present study reveals the great variability between legume germplasms in the ability to fix N₂ at different inorganic N levels, and also the potential that exists in breeding for nitrogen fixation associative traits. The¹⁵N methodology offers a unique tool to evaluate germplasms directly in the field for their N₂ fixation abilities at different N fertilizer levels.     

Rice performance and natural infection with blast (Pyricularia oryzae Cav.) under different algalization techniques and rates of fertilizer nitrogen

Japonica rice, Giza 171, was inoculated with either a dry or fresh soil-based inoculum of cyanobacteria containingAnabaena cylindrica, Anabaena oryzae, Nostoc muscorum andTolypothrix tenuis together with fertilization with urea at 0, 36, 72, or 108 kg N/ha. Fresh inoculum enhanced plant growth, yield and N content in comparison with the dry one. The efficiency of nitrogen utilization from the urea at all N concentrations was improved by using the fresh inoculum. Natural infection with leaf and neck blast caused byPyricularia oryzae Cav. increased with increasing N fertilization. Algalization with the fresh inoculum decreased leaf blast while neck blast was slightly higher in the algalized sub-plots but without considerable yield damage.     

Nitrogen fixation in soybean as influenced by cultivar and Rhizobium strain

Summary The¹⁵N-substratum labeling technique and other indirect methods were used to compare nitrogen (N₂) fixation in soybean varieties grown in the field in Greece and Romania. Significant variation in the amount (Ndfa) and proportion of N derived from fixation (% Ndfa) was found in different varieties. With 20 kg N/ha applied to soil, N₂ fixed ranged from 22 to 236 kg N/ha in Greece and from 17 to 132 kg N/ha in Romania. In general, varieties or treatments with higher dry matter yield supported greater fixation. Also, varieties with high Ndfa had high % Ndfa andvice versa. Breeding N₂-fixing legumes for high yields at low soil N levels therefore appears to be a reasonable strategy for enhancing N₂ fixation. Heavy applications of inorganic N fertilizer severely depressed N₂ fixation in two out of the three varieties used in Romania. One variety, F 74–412, however, derived slightly higher amounts of N₂ from fixation at 100 kg N/ha rate than when fertilized with 20 kg N/ha. In Greece, Chippewa, Williams and Amsoy-71 inoculated with a Nitragin inoculant fixed similar amounts of N₂ at both 20 and 100 kg N/ha fertilizer rates. However, when Chippewa and Williams were inoculated with amother, locally-isolated Rhizobium strain, N₂ fixation was substantially depressed at the higher N rate.     

Nitrogen fixation by Spirillum sp. from rice roots

Nitrogen fixation by Spirillum sp. obtained from the roots of rice plants grown at different levels of combined nitrogen was studied. The roots of rice plants exposed to low levels of combined nitrogen (20–40 kg N/ha) harboured Spirillum sp. possessing higher nitrogen-fixing efficiency as compared to the cultures from plants receiving 60–100 kg N/ha. More-over, the nitrogen-fixing efficiency of these Spirillum spp. varied with age of the plant, irrespective of the dosage of combined nitrogen.     

Soil and litter respiration rates in different microhabitats of a mixed oak-conifer forest and their control by edaphic conditions and substrate quality

Summary Seven isolates belonged toA. brasilense and 3 belonged toA. lipoferum. Isolates having more denitrifying capacity fixed less nitrogen in nitrogen free semi-solid malate medium. One strain ofA. lipoferum having high nitrogen fixing capacity with negative test for denitrification was tested as inoculant to supplement the nitrogen need of a wheat crop in field condition with different doses of N with and without the inoculant. While control without nitrogen yielded 1260 kg/ha the yield in inoculated treatment was 2070 kg/ha resulting in significant increase. In a treatment receiving 40 kg N/ha the grain yield was 2370 kg/ha as against yield of 3110 kg/ha in a similar treatment receiving fertiliser plus inoculant. Thus increase in yield was about 30%. Further the treatment receiving 80 kg N/ha yielded 2970 kg/ha as against yield of 4150 kg/ha in a treatment receiving inoculant alongwith the above dose of the fertiliser. Thus increase in yield due to application of inoculant was about 36%. Similarly, the uptake of N in different treatments was augmented due to inoculation of seeds with the culture.     

Experimental formulations ofBacillus sphaericus for the control of anopheline and culicine larvae

Summary Four experimental formulations ofBacillus sphaericus Neide (2362 isolate) were evaluated for larvicidal activity against culicine and anopheline larvae in several natural and artificial habitats. A granular formulation (5% primary powder) was tested against natural populations of mosquitoes in two simulated habitats in Florida and in maturing and reflooded rice fields in Louisiana. Larvae ofCulex quinquefasciatus Say were reduced by 97 and 99% after application of the granules at the rate of 10 kg/ha to polluted tanks and 2.5 kg/ha to sod-lined potholes, respectively. Anopheline andPsorophora columbiae (Dyar and Knab) larvae were reduced by 68 and 92–100%, respectively, after application of 5 kg granules/ha to rice fields. A flowable concentrate (12.8% primary powder) applied to unpolluted and organically enriched habitats in Florida at 0.25 kg/ha reduced populations ofCulex spp. by 93–100% and 99%, respectively. Sustained-release briquets (5% primary powder) applied at the rate of one half briquet/1.8 m² sod-lined potholes reduced larval populations ofCx. quinquefasciatus by 88–95% for up to 2 weeks in open sunlight. Sustained-release pellets (30% primary powder) applied to small woodland pools in Memphis, TN at the rate of four pellets/pool virtually eliminated larval populations ofCx. restuans Theobald for over 8 days. Variable persistance of larvicidal activity was noted for the other treatments depending on the formulation, target species and habitat.     

Interactive effects of exogenous combined nitrogen and phosphorus on growth and nitrogen fixation by azolla

Effects of N source and media-N and P levels were examined on growth, N uptake, and N₂ fixation ofAzolla pinnata withAnabaena azollae association (azolla) at two inoculum-P concentrations. Each expeiment was conducted for 7 days in a growth chamber using azolla at a predetermined inoculum-P concentration and the growth media containing a combination of four levels of P (0, 15, 75, and 200 M) and three levels (0, 1, and 5 mM) of either¹⁵N-enriched NH ₄ ⁺ as ammonium sulfate or¹⁵N-enriched NO ₃ ^– as potassium nitrate. Nitrogen uptake and N₂ fixation were measured by¹⁵N isotopic dilution method. Tissue P and N, N uptake, and N₂-fixation increased with increasing P concentration in the media regardless of the inoculum-P level of azolla. Increasing P concentration in the media increased growth of azolla at low inoculum P, but the effect on high inoculum-P azolla was either small or absen. High inoculum-P concentration resulted in increased growth, tissue-N and P concentrations, N uptake, and N₂ fixation by azolla. Ammonium in the growth media caused larger increase in tissue-N and greater repression of N₂ fixation than equimolar concentration of NO ₃ ^– . In the presence of NH ₄ ⁺ or NO ₃ ^– , in the growth media, N uptake by azolla exceeded the corresponding decrease in N₂ fixation, resulting in an overall increase in tissue-N concentration. Phosphorus in the media tended to negate the inhibitory effect of NH ₄ ⁺ or NO ₃ ^– on N₂ fixation. A multiple regression model showed that the effect of tissue-N on N₂ fixation was negative while that of tissue-P was positive. Therefore, a relative change in tissue-N and P appeared to regulate N₂ fixation. Tissue-N and P had similar effects on relative growth rate of azolla also. Inoculum-P level of azolla was important in determining the response to media-P.This research was supported by a grant from USAID under Indo-US Science and Technology Initiative.     

Comparison of isotope techniques and non-nodulating isolines to study the effect of ammonium fertilization on dinitrogen fixation in soybean,Glycine max

Summary Two experiments were carried out with two nodulating and non-nodulating soybean isolines, with three different levels of N as (¹⁵NH₄)₂SO₄ at the equivalent of 0, 25 and 50 kg N/ha. In the first experiment three seeds were sown in each pot and the plants harvested at 35, 55 and 75 days. In the second experiment only one seed was sown per pot and harvested at 75 days.Isotope dilution technique and in certain cases natural isotope variation (¹⁵N) was used to determine directly the origin of nitrogen in the plant, whether from soil, fertilizer or biological N₂-fixation. The use of nodulating and non-nodulating isolines enabled comparison with the classical method of estimating N₂-fixation by difference from total plant N. Results at the 75 day harvest were similar for either method, but at the earlier harvests, particularly at 35 days, the total-N method was inadequate. The isotope method appeared more sensitive while the total-N method suffered from greater variability with correspondingly high standard errors and significant differences.It was found that by the 35 and 55 day harvests hardly any N₂-fixation had taken place, plant nitrogen being almost entirely derived from soil or fertilizer N. Plants in competition used up soil fertilizer N more rapidly, thus stimulating symbiotic nitrogen fixation. When only one plant was grown in each pot it had a greater proportion of N derived from soil or fertilizer, and less N derived from fixation. In general the¹⁵N data showed that only about 25% of the applied fertilizer N was absorbed by the plant.The nodulating isoline absorbed more N than the non-nodulating plants. This suggests a possible synergistic effect of N₂-fixation on N derived from other sources, giving an increase in total-N content of nudulated plants. The N derived from N₂-fixation was scarcely detectable in the roots but appeared to be translocated almost entirely to shoots and pods.With 25 kg N/ha the greater proportion of the nitrogen in the pods was derived from N₂-fixation. Even with 50 kg N/ha the nitrogen in the pods derived from fixation remained high, that being derived from fertilizer being less than 15%. About 80% of the nitrogen in the nodules was due to fixation.In the present experiment the application of 25 kg N/ha appeared sufficient to give maximum N absorption by both isolines. At this level symbiotic fixation by Rhizobium remained high in nodulating plants, while the proportion of total N due to fixation was reduced with 50 kg N/ha.UNDP/IAEA Project BRA 78/006.     

Influence of urea on biological N2 fixation and N transfer from Azolla intercropped with rice

The N₂ fixed by Azolla before and after urea application during the rice cycle, the mineralisation of Azolla-N as well as its availability to rice was studied in two greenhouse experiments conducted in 1996 and 1997 and in June 1998 in Goettingen (Germany). Dry matter production of the various rice parts of experiment 1 showed a clear positive synergism between treatment with Azolla and urea with a resulting apparent N recovery by rice increasing from 40% (without Azolla) to 57% in the presence of Azolla. Part of this increase may be due to N fixed biologically by Azolla and transferred to the rice. The second experiment shed some light on the role of BNF. Using an iterative method of estimation, the daily rate of N fixation was estimated at 0.6 – 0.7 kg N ha^–1. The rate was not so much affected by the age of the Azolla crop. At this rate, the BNF would amount to up to 100 kg N ha^–1 over a 130-day season. Assuming that BNF may be inhibited for a period of 5 – 10 days following urea application due to high levels of N in the floodwater, this might reduce the BNF by between 6 and 14 kg N ha over the season. Using the mean-pool-abundance concept, it was estimated that around 75 – 80% of the Azolla-N mineralized during the growth period was actually absorbed by the rice plants. Of the N taken up by rice around 28% was derived from the biologically fixed Azolla N, the remainder was urea N cycled through the Azolla. Azolla also seems to help sustain the soil N supply by returning N to the soil in quantities roughly equal to those extracted from the soil by the rice plant.     

Soybean yield response to residual NO3−N and applied N

Summary During 1976 through 1978, 10N treatments (combinations of N application times and rates) were used in a corn study. Those treatments created different levels of soil NO ₃ ^– –N content that were well-suited to a study of the influence of residual NO ₃ ^– –N and applied N on soybean yield. In April 1979 we applied ammonium nitrate at rates of 0, 75, or 150 kg N/ha to three subplots formed from each of the whole plots (previous N treatment plots). With N fertilization in 1979, seed yield increased where the residual NO ₃ ^– –N amount was less than 190 kg/ha but decreased where the residual amount was greater than 190 kg/ha. As the NO ₃ ^– –N content in the soil increased by 1 kg/ha, the soybean yield increase due to N fertilization in 1979 decreased by approximately 4 kg/ha.Contribution no. 82-368-J, Dep. of Agronomy, Kansas Agric. Exp. Stn., Manhattan, KS 66506, USA     

Mineral N effects on cowpea and soybean crops in a Nigerian soil

Summary In a Nigerian soil depleted in available N, fertilizer-N enriched in¹⁵N was applied at 25 and 100 kg N/ha to crops of four cowpea and two soybean cultivars. Soil-N availability was estimated with three non-fixing crops, non-nodulating soybean, maize and celosia. With sequential harvests we examined the development of the fixing crops, as well as their nodulation profiles and acetylene reduction activities, and the patterns obtained were correlated with uptake of mineral-N. At low levels of mineral-N, excellent nodulation (up to 580 mg dry weight/plant) and very high acetylene reduction activities (up to 208 μmoles/plant/h) were recorded. Although fertilizer-N utilizations were low, 12% and 28% at 25 and 100 kg N/ha respectively, the lower application had a transient adverse effect on nodule development and the higher application had a long-term adverse effect on nodule formation, nodule development and acetylene reduction activity. Cowpea nodule mass reached maximum levels at early pod-fill except at 100 kg N/ha at which it continued to increase into late podfill. In contrast, soybean nodulation did not peak at any level of N but increased into late pod-fill.     

Soil nitrogen dynamics in a holm oak forest

Soil nitrogen (N) dynamics were studied in a dense, holm oak (Quercus ilex ssp. ilex) stand in the Montseny mountains to determine annual and seasonal patterns of N availability and uptake in an undisturbed Mediterranean forest on acidic soil. Soil mineral N content, net N mineralization (NNM), and net nitrification (NN) were determined by monthly sampling at two soil depths followed by in situ incubation in polyethylene bags. NNM per unit of soil mass was much higher at 0–5 cm than at 5–20 cm (annual means 24 and 2.5 mg N/kg, respectively) but on an area basis NNM was similar at both depths. A total of 80 kg N/ha/yr were mineralized from the first 20 cm of soil. NN amounted to only 9% of the annual NNM (7.5 kg N/ha/yr) and it occurred only in the upper 5 cm. NNM was maximum in June and July, while the NN peaked in May. Despite favourable soil temperature and moisture, NNM was negative in autumn because of microbial immobilization. Seasonal and depth variations of NNM appeared to be controlled more by substrate quality than by organic matter quantity, temperature or moisture. NN was not limited by ammonium availability. Calculated N uptake amounted to 91 kg/ha yr, peaking in June and July. The investigated stand showed a moderately high N availability, but ammonium was the major form of mineral N supply for holm oak.