Five varieties of groundnuts were studied for their exact amount of nitrogen fixation effect on subsequent sorghum crop. The 15N methodology was used with a non-nodulating groundnut isoline as the reference crop. Six months after the groundnut harvest, sorghum was sown to study the presence of any residual N from fixation and/or soils own conserved N. The non-nodulating groundnut as a reference crop could detect N fixation (Ndfa) as amounting to 60% —70% of the crops need, i.e., 20%-30% more than the 40% -50% detected using sesame as the reference crop. The N derived from soil (Ndfs) was reduced from 50%-60% to 30%-40% which is much closer to what the low N (300ppm) Gezira soil can provide. Subsequent sorghum was positively affected by the preceding groundnut varieties but only variety Medani gave significant straw and total biological yields over the non-nodulating isoline. There was, therefore, an indication of residual N represented by the higher parameters recorded for the varieties. Groundnut is thus a good preceding crop for cereals though more research work is needed in the area of biological nitrogen fixation

A.M. Adlan, Mohamed

O. Mukhtar, Nuri

English

Journals Of University Of Gezira

Gezira Journal of Agricultural science                                   Vol. 1(1) 2003  32  Measuring N2- fixation by some varieties of groundnut and their residual effect on subsequent sorghum crop using 15N methodology  Mohamed A.M. Adlan and Nuri O. Mukhtar  Land and Water Research Centre, Agricultural Research and Technology Corporation, P.O. Box 126, Wad Medani, Sudan.  ABSTRACT      Five varieties of groundnuts were studied for their exact amount of nitrogen fixation effect on subsequent sorghum crop. The 15N methodology was used with a non-nodulating groundnut isoline as the reference crop. Six months after the groundnut harvest, sorghum was sown to study the presence of any residual N from fixation and/or soils own conserved N. The non-nodulating groundnut as a reference crop could detect N fixation (Ndfa) as amounting to 60% —70% of the crops need, i.e., 20%-30% more than the 40% -50% detected using sesame as the reference crop. The N derived from soil (Ndfs) was reduced from 50%-60% to 30%-40% which is much closer to what the low N (300ppm) Gezira soil can provide. Subsequent sorghum was positively affected by the preceding groundnut varieties but only variety Medani gave significant straw and total biological yields over the non-nodulating isoline. There was, therefore, an indication of residual N represented by the higher parameters recorded for the varieties. Groundnut is thus a good preceding crop for cereals though more research work is needed in the area of biological nitrogen fixation.  INTRODUCTION The land endowment of the Sudan is estimated at 96 million hectares arable land with only about 11.5 million hectares under cultivation. The Gezira is the largest irrigated scheme (0.84 million ha) in the country. It contributes a big share in food provision. A defined crop rotation is practiced in the scheme including cotton, wheat , groundnuts , sorghum and fallow in this order. Limited areas are grown to horticultural crops and forages  Gezira Journal of Agricultural science                                   Vol. 1(1) 2003  32       Groundnut was introduced as a legume in the rotation for soil fertility preservation but it proved to be a good food in the form of cooking oil, animal feed as cake concentrates and as an export  crop only second to cotton for fetching hard currency.      Research in biological nitrogen fixation (BNF) by groundnuts has received good attention since its introduction in the country, in the early 1950's. The studies conducted defined the problems encountered in the field of improving BNF by groundnuts. One of these problems is the belief that the crop is not a good N2-fixing legume inspite of the fact that sorghum grown following groundnuts gave better yields compared to sorghum after cereals, cotton and other crops at Rahad research station (Fadil A/Rahman, personal communication). Also soil analysis immediately after the harvest of a number of crops  showed that available N03-N was double under groundnut compared to maize and sorghum at Kenana research station (Mukhtar, 1973).      Nitrogen fixation was always measured by the conventional N difference method (Musa, 1974; Hadad, 1984). An experiment using 15N methodology gave the best fixation as about 50% of the crop's N need with sesame as the reference crop (Mukhtar, 1993 Many experiments showed that the crop responded neither to combined nitrogen nor to seed inoculation with rhizobia (Musa, 1974; Mukhar, (1982 a fact that clearly showed the 50% fixation recorded was very low. In addition to that, a crop of groundnut yields about 180kg N/ha meaning that at least 90 kg of N are provided from the soil which is already known to be low in N (300 ppm). Considering reports of 64%, 78 %  and 92% N-fixed by this crop (Boddey et al., 1990; Gilla et al., 1987, and Nurhayati et al., 1991), it is clear that N-fixation by groundnuts is not well tapped here. The major factor in studying exart N-fixation using 15N methodology is the reference crop used (Danso,   (. 1988 Sesame which was used as a reference crop in earlier studies was replaced by a non-nodulating groundnut isoline in the present work.       The objectives of this study are: a) to determine the exact N fixation by five groundnut varieties that already showed differences in nodulation (Adlan and Mukhtar, 1998 ) using a non-nodulating  groundnut as a reference crop, b) to investigate the effect of preceding groundnut varieties on subsequent sorghum production through N residual effect.   Gezira Journal of Agricultural science                                   Vol. 1(1) 2003  32  MATERIALS AND METHODS     Five groundnut varieties, MH383, Medani, Ahmedi, Kiriv, and Virginia Red together with a non-nodulating isoline were sown at the Gezira Research Farm, Wad Medani, Sudan, on 15 of June 1999 in micro-plots of 2.4m2  situated at one end of a macro-plot of 4x6 m2 .  The nitrogen fixing varieties were given the equivalent of 20 kg N/ha in the form of urea with 5.4% 15N atom excess (excess over the natural 15N abundance) while the isoline was given 100kg N/ha at 1.0% 15N atom excess.  All plots were arranged in a randomized complete block design (RCBD) replicated four times. The crop  was sown  in a spacing of 60x15cm with two seeds per hole.. Watering was effected every 14  days.     Fresh weight dry matter, nodulation and pod yield were the parameters studied from the main plot while data for N-flxation was collected form a sampling) area of I x 2m2- within the microplot. Nodule counts and dry weight were measured 72 days after sowing. Ten plants were randomly taken at harvest from the center of the microplots for  the 14N/ 15N analysis. Plant tissue samples together with the diluted 15N used were sent to the International Atomic Energy Agency (IAEA( laboratories at Sibersdorf, Vienna, for 14N/ 15 N analysis by the emission spectrometer.      After the harvest of groundnuts, all the experimental plots were sown to sorghum (var. Ingaz) after the lapse of  period of 6 months. The plots were used with minimum tillage so as not to lose their boundaries.  Samples of sorghum from microplots taken at harvest were subjected to 15N  analysis and grain yield and its components  were estimated under each genotype from the macro-plots. The data were subjected to analysis of variance procedure and mean separation done using Duncan's Multiple Range Test (DVIRT). RESULTS AND DISCUSSION      No significant differences were obtained for the N percent, %15N atom excess and nodule number per plant among the varieties (Table l). Virginia Red, however, gave significantly more nodule dry weight over the others. While Kiriz gave significantly the lowest biomass, Medani gave the highest biomass. This could be an indication of better N fixation (Rochester et al., 1998). Kiriz, again, gave the least total nitrogen compared to the highest one produced by Medani (Table 2). Gezira Journal of Agricultural science                                   Vol. 1(1) 2003  32  Table l. %N, % BN at01n excess, nodule number/plant and dry plant and the total biomass of five groundnut varieties. Varieties %N %15N atom excess Nodule number/plant Nodule dry weight (g/plant) Total Biomass (kg/ha) MH 383 2.14 a 0.103 a 457 a 0.615b 8663 a Kiriz 2.10 a 0.115 a 295 a 0.580 b 5295 h Medani 2.16 a 0.096 a 298 a 0.500 b 8723 a Ahmedi 2.32 a 0.080 a 423 a 0.625 b 7630 a V. Red 2.03 a 0.108 a 532 a 0.040a 7794 a  Means followed by the same letter(s) in each column are not significantly different according to Duncan's Multiple Range Test (DMRT( .   Table 2. Total plant N, %N derived from soil and air and kg  N/ha fixed and/or taken from the soil. Varieties  Total Plant N (kg/ha) Ndfa Fix (%) Ndfs (kg N/ha) Ndfs  Kg N/ha) Ndfs (%) MH 383 185.6 a 65.0 a 120.5 a 61.5 a 33.0 a Kiriz 111.5b 59.7 a 68.7 b 40.5 a 38.1 a Medani 187.9 a 660 a 124.3 a 60B a 32.2 a Ahmedi 177.9 a 72.4 a 128.0 a 47.3 a 26.1 a V. Red 158.1 a 61.6 a 98.0 ab 569 a 36.4 a  Means followed by the same letter (s) in each column are not significant different according to Duncan's Multiple Range Test (DMRT(      The %N derived from the atmosphere (Ndfa) was lowest for  Kiriz and highest for Ahmedi (Table 2). The non-nodulating reference  has therefore, attained 60%/-70%/ fixation which was far higher and within good fixation limits compared to the 40% - 49% shown before )Mukhtar, 1993) using sesame as the reference crop, i.e., fixation had  risen 20%. On the other hand, nitrogen derived from soil (NDFS  ( dropped from 90 kg N/ha (for a 180 kg/ha total uptake) to 40-60 kg N/ha (Table 2) much closer figures, though still higher, to what the Gezira soil could provide.  Gezira Journal of Agricultural science                                   Vol. 1(1) 2003  32   The difference in BNF, %N derived from  air  between  the highest value recorded by Ahmedi and the lowest attained by Kiriz was about 14.7%. Nitrogen derived from soil (Ndfs) was lowest for Ahmedi and f highest for Kirjz Significant differences in BMF were observed among the  genotypes with Kiriz fixing the least and Ahmedi the most )Table 2), but there were no significant differences in Ndfs among the genotypes.     Though residual nitrogen is better studied after the  incorporation of legume residue, stover removal  causes net removal of N from the soil (Eaglesham et al., 1982; Senaratne and Hardarson, 1988). Yet the results without stover incorporation revealed significant differences for the effect of the preceding Medani groundnut variety on the straw and total biomass yields of the subsequent sorghum over those of Kiriz and the non-nodulating cultivars while MH 383, Ahmedi and V. Red all gave significantly more   sorghum straw than Kiriz only, but they exceeded the non-nodulating isoline by 16%, 25% and 21%, respectively (Table 3).  Table 3. Effect of different preceding groundnut varieties on seed and straw yields and total biomass of subsequent sorghum Varieties  Seed yield (kg/ha) Straw yield (hg/ha) Total Hiomass (kg/ha) MH383 2151 a 13402 ab 15555 ab Non-nodutlating    isoline 2138 a 11544 bc 13682 bc Kiriz 1783 a 10277 c 12060 c Medani 2189 a 15920 a 18109 a Ahmedi 1944 a 14403 ab 16347 ab V. Red 2238 a 13970 ab 16208 ab  Means followed by the same letter(s) in each column are not significantly different according to Duncan's Multiple Range Test (DMRT(.       Total biomass gave the same results as those for the straw yield. Sorghum seed yield, however, did not show any significant residual genotype effect. Seed yield, %N and total N yield were not affected by any residual N while the % 15N atom excess showed significant differences for the sorghum following the different variety ( Table4). Ahmedi and Virigina Red had the Gezira Journal of Agricultural science                                   Vol. 1(1) 2003  32  highest %15N atom excess while the lowest %15N atom excess was recorded for the non-nodulating  isoline followed by Kiriz, Medani and then MH 383.  Table 4. Effect of different preceding groundnut varieties on %N, total N uptake and % 15N atom excess of subsequent sorghum. Varieties  %N Total N uptake (kg/ha) %15N atom excess MH383 0.832 a  128.8 a  0.026 a  Non-nodulating    isoline 0.850 a 117.7 a 0.022 b Kiriz 0.830 a 100.3 a 0.024 ab Medani 0.800 a 145.0 a 0.025 ab Ahmedi 0.715 a 116.7 a 0.031 a V. Red 0.725 a 116.5 a 0.031 a  Means followed by the same letter(s) in each column are not  significantly different according to Duncan's Multiple Range Test (DMRT).       It was expected that the lowest %15 N atom excess should indicate the highest residual nitrogen expressed in total N-uptake, biomass and seed production, but this was not the case. Such results were obtained when stover of non-labeled legume was added to dilute  15N atom excess of the residual soil nitrogen (Senaratne and Hardarson, 1988).  In this study, the erratic results were due to the dependence of the sorghum crop on the labeled nitrogen that was left over by the previous legume crops. Here again the non-nodulating crop which was previously given 100 kg N/ha at 1.0% 15N atom excess gave the  lowest %15 N atom excess for sorghum. A result which conformity with the total nitrogen uptake where the least total N was taken up by the non-nodulating groundnut isoline. The latter was not significantly different under the different genotypes, though MH 383 and Medani produced much more total N and total biomass, respectively compared to total N and biomass produced by the non-nodulating isoline.      There was, however, an indication of residual N as many varieties significantly out-yielded the non-nodulating isoline in straw and total biomass production. Gezira Journal of Agricultural science                                   Vol. 1(1) 2003  32      In conclusion, groundnut was a good fixing crop. It could fix up to 72% of it's  N requirement. Furthermore, the varieties tested showed  genotypic differences in N —fixation, effect on subsequent sorghum production and residual N. Residual N could, however, come from the  two sources of fixed and non-fixed and components (Chalk, 1998). REFERENCES  Adlan, M.A.M. and N.O. Mukhtar. 1998. Genotypic differences in groundnut nodulation. Annual Report, Gezira Research Station (GRS), Agricultural Research Corporation (ARC), Wad Medani,  Sudan. Boddey, R.M., S. Urquiaga and M.C.P. Neves. 1990. Quantification of N 2 fixation to field grown legumes - a strategy for the practical of the 15 N isotope dilution technique. Soil Biology and Biochemistry 22: 649-655 .  Chalk, P.M. 1998. Dynamics of biologically fixed N in legume –ceveal rotations :a review. Australian Journal of Agricultural Research  49:303-316. Danso, S.K.A. 1988 The use of  15N enriched fertilizers for estimating nitrogen fixation in grain and pasture leglllnes, pp 345-358. In: D.P. Beck and L.A. Materon (eds). Nitrogen Fixation by Legumes in Mediterranean Agriculture. Netherlands.  Eaglesham A.R. J, A. Ayanaba, V. Ranga Rao, and D.L. Eskew 1982 Mineral N effect on cowpea and soybean crops in a Nigerian soil, ll, Amounts of  fixed and accrual to the soil. Plant and soil 68:183-192. Giller,K.E,  P.T.C.  Nambari Rao. B. Sirniumsa, P.J. Dart and J.M  Day  1987  .   N2-fixation in genotypes of groundnuts (Arachis hypogaea L.) compared using 15N isotope dilution. Biology and Fertility  of Soils 5:23-25.  Hadad M.A. 1984. Groundnut (Arachis hypogaea L.) inoculation in the Sudan. Ph.D. Thesis, Iowa State University, USA.  Mukhtar, N.O. 1973. Distribution of soil nitrates under the continuous         monocropping, long term NPK experiment, pp. 87. Annual Report KRS/ARC, Wad Medani, Sudan.  Mukhtar, N.O. 1982. Nitrogen fixation in food legumes ICARDA/ NVRP. Annual Coordination Meeting Cairo -Egypt. Mukhtar N.O. 1993. Evaluation of the time course of N2-fixation and amount of  N2-fixed   by two varieties of groundnuts (Arachis hypogea Gezira Journal of Agricultural science                                   Vol. 1(1) 2003  23  L.) using 15N dilution  method. Annual Report GRS/ARG, Wad Madani, Sudan. Musa, M.M. 1974. Groundnut inoculation and N P fertilization. Annual Report GRS/ARC. Madani, Sudan. Nurhayati, D.P. A.W. Faizah, M.N. Sudan and D.F. Herridage. 1991.  Use of natural enrichment of  15N in plant available soil nitrogen for measurement of symbiotic N2-fixation.  In IAEA/FAO Stable Isotopes in Plant Nutrition; Soil Fertility and Environment Studies, IAEA. Vienn, pp. 117-130. Rochester, I.J., M.B. Peoples, G.A. Constable and R.R. Gault. 1998. Faba beans and other legumes add nitrogen to irrigated cotton cropping systems.  Australian Journal of Experimental Agriculture 38(3): 253-260. Senaratne, R. and G. Hardarson 1988. Estimation of residual nitrogen effect of faba bean and  pea on two succeeding cereals using 15N methodology. Plant and soil 110:81-89.  

Measuring N2- Fixation by some Varieties of Groundnut and their Residual Effect on Subsequent Sorghum Crop using 15N Methodology

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Measuring N2- Fixation by some Varieties of Groundnut and their Residual Effect on Subsequent Sorghum Crop using 15N Methodology

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