Sowing time and tillage practice affect chickpea yield and nitrogen fixation. 2. Nitrogen accumulation, nitrogen fixation and soil nitrogen balance

1996 ◽  
Vol 36 (6) ◽  
pp. 701 ◽  
Author(s):  
CP Horn ◽  
RC Dalal ◽  
CJ Birch ◽  
JA Doughton

Following long-term studies at Warra, on the western Darling Downs, chckpea (Cicer anetinum) was selected as a useful grain legume cash crop with potential for improvement of its nitrogen (N) fixing ability through management. This 2-year study examined the effect of sowing time and tillage practice on dry matter yield, grain yield (Horn et al. 1996), N accumulation, N2 fixation, and the subsequent soil N balance. Generally, greater N accumulation resulted from sowing in late autumn-early winter (89-117 kg N/ha) than sowing in late winter (76-90 kg N/ha). The amount of N2 fixed was low in both years (15-32 kg N/ha), and was not significantly affected by sowing time or tillage. The potential for N2 fixation was reduced in both years due to high initial soil nitrate levels and low total biomass of chickpea because of low rainfall. Nitrogen accumulation by grain was higher under zero tillage (ZT) than conventional tillage (CT) for all sowing times, and this affected the level of grain N export. The consequence of low N2 fixation and high N export in chickpea grain was a net loss of total soil N, (2-48 kg N/ha under CT and 22-59 kg N/ha under ZT). Management practices to ensure larger biomass production and lower soil nitrate-N levels may result in increased N2 fixation by chickpea and thus a positive soil N balance.

2001 ◽  
Vol 41 (3) ◽  
pp. 347 ◽  
Author(s):  
J. Evans ◽  
A. M. McNeill ◽  
M. J. Unkovich ◽  
N. A. Fettell ◽  
D. P. Heenan

The removal of nitrogen (N) in grain cereal and canola crops in Australia exceeds 0.3 million t N/year and is increasing with improvements in average crop yields. Although N fertiliser applications to cereals are also rising, N2-fixing legumes still play a pivotal role through inputs of biologically fixed N in crop and pasture systems. This review collates Australian data on the effects of grain legume N2 fixation, the net N balance of legume cropping, summarises trends in the soil N balance in grain legume–cereal rotations, and evaluates the direct contribution of grain legume stubble and root N to wheat production in southern Australia. The net effect of grain legume N2 fixation on the soil N balance, i.e. the difference between fixed N and N harvested in legume grain (Nadd) ranges widely, viz. lupin –29–247 kg N/ha (mean 80), pea –46–181 kg N/ha (mean 40), chickpea –67–102 kg N/ha (mean 6), and faba bean 8–271 kg N/ha (mean 113). Nadd is found to be related to the amount (Nfix) and proportion (Pfix) of crop N derived from N2 fixation, but not to legume grain yield (GY). When Nfix exceeded 30 (lupin), 39 (pea) and 49 (chickpea) kg N/ha the N balance was frequently positive, averaging 0.60 kg N/kg of N fixed. Since Nfix increased with shoot dry matter (SDM) (21 kg N fixed/t SDM; pea and lupin) and Pfix (pea, lupin and chickpea), increases in SDM and Pfix usually increased the legume’s effect on soil N balance. Additive effects of SDM, Pfix and GY explained most (R2 = 0.87) of the variation in Nadd. Using crop-specific models based on these parameters the average effects of grain legumes on soil N balance across Australia were estimated to be 88 (lupin), 44 (pea) and 18 (chickpea) kg N/ha. Values of Nadd for the combined legumes were 47 kg N/ha in south-eastern Australia and 90 kg N/ha in south-western Australia. The average net N input from lupin crops was estimated to increase from 61 to 79 kg N/ha as annual rainfall rose from 445 to 627 mm across 3 shires in the south-east. The comparative average input from pea was 37 to 47 kg N/ha with least input in the higher rainfall shires. When the effects of legumes on soil N balance in south-eastern Australia were compared with average amounts of N removed in wheat grain, pea–wheat (1:1) sequences were considered less sustainable for N than lupin–wheat (1:1) sequences, while in south-western Australia the latter were considered sustainable. Nitrogen mineralised from lupin residues was estimated to contribute 40% of the N in the average grain yield of a following wheat crop, and that from pea residues, 15–30%; respectively, about 25 and 15 kg N/ha. Therefore, it was concluded that the majority of wheat N must be obtained from pre-existing soil sources. As the amounts above represented only 25–35% of the total N added to soil by grain legumes, the residual amount of N in legume residues is likely to be important in sustaining those pre-existing soil sources of N.


1996 ◽  
Vol 36 (6) ◽  
pp. 695 ◽  
Author(s):  
CP Horn ◽  
CJ Birch ◽  
RC Dalal ◽  
JA Doughton

Mean protein concentrations in wheat (Triticum aestivum) on the Darling Downs of southern Queensland have fallen below 10% in recent years, preventing farmers from obtaining 'Prime Hard' status (13.0%) for their wheat crop. Two management options, for improving this situation are applications of nitrogenous fertiliser in a wheat monoculture or inclusion of a legume in rotation with wheat. Long-term trials at Warra, on the western Darling Downs, resulted in the selection of chickpea (Cicer arietinum) as a useful grain legume cash crop with potential for improvement of its nitrogen (N) fixing ability through management. This 2-year study examined the effect of sowing time and tillage practice on dry matter yield, grain yield, N accumulation and N2 fixation in chickpea and the subsequent soil N balance. There were 3 sowing times during autumn and winter of each year using conventional tillage (CT). Zero tillage (ZT) was introduced after the first crop for all sowing times. Greater total dry matter yield and grain yield (4.18-5.95 and 1.63-2.25 t/ha, respectively) resulted from sowing in autumn or early winter than from sowing in late winter (3.39-3.86 and 0.97-1.22 kg/ha, respectively). The effects of tillage practice were variable, depending on growth stage. At harvest, ZT plots produced greater total dry matter yield (4.20 t/ha) and grain yield (1.94 t/ha) than CT plots (3.01 and 1.29 t/ha, respectively), whereas at the time of maximum dry matter, yield was higher under CT for autumn sowings, and under ZT for winter sowings.


1997 ◽  
Vol 37 (6) ◽  
pp. 667 ◽  
Author(s):  
W. M. Strong ◽  
R. C. Dalal ◽  
J. E. Cooper ◽  
J. A. Doughton ◽  
E. J. Weston ◽  
...  

Summary. Continuous cereal cropping in southern Queensland and northern New South Wales has depleted native soil nitrogen fertility to a level where corrective strategies are required to sustain grain yields and high protein content. The objective of this study was to examine the performance of chickpea in chickpea–wheat rotations in terms of yields, water use and N2 fixation. The effects of sowing time and tillage practice have been studied. Chickpea grain yields varied from 356 kg/ha in 1995 to 2361 kg/ha in 1988; these were significantly correlated with the total rainfall received during the preceding fallow period and crop growth. Almost 48% of total plant production and 30% of total plant nitrogen were below-ground as root biomass. Mean values of water-use efficiency for grain, above-ground dry matter, and total dry matter were 5.9, 14.2 and 29.2 kg/ha.mm, respectively. The water-use efficiency for grain was positively correlated with the total rainfall for the preceding fallow and crop growth period although cultural practices modified water-use efficiency. The potential N2 fixation was estimated to be 0.6 kg nitrogen/ha.mm from 1992 total dry matter nitrogen yields assuming all of the nitrogen contained in chickpea was derived from the atmosphere. Sowing time had a much larger effect on grain yield and N2 fixation by chickpea than tillage practice (conventional tillage and zero tillage) although zero tillage generally increased grain yields. The late May–early June sowing time was found to be the best for chickpea grain yield and N2 fixation since it optimised solar energy use and water use, and minimised frost damage. Nitrogen fixation by chickpea was low, less than 40% nitrogen was derived from atmosphere, representing less than 20 kg nitrogen/ha.year. The potential for N2 fixation was not attained during this period due to below-average rainfall and high soil NO3-N accumulation because of poor utilisation by the preceding wheat crop. Increased soil NO3-N due to residual from fertiliser N applied to the preceding wheat crop further reduced N2 fixation. A simple soil nitrogen balance indicated that at least 60% of crop nitrogen must be obtained from N2 fixation to avoid continued soil nitrogen loss. This did not occur in most years. The generally negative soil nitrogen balance needs to be reversed if chickpea is to be useful in sustainable cropping systems although it is an attractive cash crop. Sowing time and zero tillage practice, possibly combined with more appropriate cultivars, to enhance chickpea biomass, along with low initial soil NO3-N levels, would provide maximum N2 fixation.


1988 ◽  
Vol 28 (1) ◽  
pp. 99 ◽  
Author(s):  
MJ Blumenthal ◽  
VP Quach ◽  
PGE Searle

The effect of soybean population density on soybean yield, nitrogen accumulation and residual nitrogen was examined at Camden, N.S.W. (34�S.). In the first experiment, treatments were soybeans (cv. Ransom) at 50, 100, 200 and 400 x 103 plants ha-1; maize (cv. XL66); and a weed-free fallow. Total dry matter yields of tops and grain yields were highest at 200x 103 plants ha-1 (6214 and 3720 kg ha-1, respectively). The yield component most affected by population density was number of branches per plant, with values decreasing with increasing population density. The proportion of unfilled pods was highest at the highest population density. Total nitrogen (N) accumulation in the tops and in the grain was also at a maximum at 200x 103 plants ha-1. The rate of dry matter accumulation declined during pod filling at all population densities. N accumulation continued at high rates throughout the growing season except in the 400x 103 plants ha-1 population. There was a trend for residual dry matter and N in residues to increase with increasing population density. After grain and forage harvest of the first experiment, a crop of wheat (cv. Kite) was sown over the whole area to determine residual N available at anthesis and at maturity (experiment 2). The values of N accumulation in the wheat at maturity were 24 kg N ha-l for the maize treatment, 40-60 kg N ha-l for the soybean treatments and 69 kg N ha-1 for the fallow treatment. Grain yield and grain N followed the pattern of dry matter production and N accumulation at final harvest. The data suggest that soybean depletes soil N to a lesser extent than does maize. For the soybean treatments, there was a trend of increasing residual N at the 3 highest population densities (40-60 kg N ha-1). This was probably a result of an increase in N in leaf fall and in decaying tops and roots at the highest population density. The high value (57 kg N ha-l) at the lowest population density may be due to soybean plants at this density not using as much soil N as the other soybean treatments. No benefit in residual N was gained from planting soybeans at a density beyond the optimum for grain yield when residues were removed by forage harvesting.


1998 ◽  
Vol 49 (3) ◽  
pp. 409 ◽  
Author(s):  
D. F. Herridge ◽  
H. Marcellos ◽  
M. B. Peoples ◽  
W. L. Felton ◽  
G. L. Turner

Functions quantifying relationships between N2 fixation by legumes and other factors would be useful to farmers in the management of legumes and nitrogen in their production systems. The 2 most critical factors regulating N2 fixation are legume yield and soil nitrate and both should be included as independent variables in the functions. Data from 9 experiments in northern New South Wales on soil nitrate at sowing, yields of shoot and grain dry matter (DM) and N of chickpea, and δ15N of shoots of chickpea and non N2-fixing reference crops (wheat, barley, and uninoculated chickpea) were used to determine the percentage of chickpea N derived from N2 fixation (P fix), total N2 fixed, and N balance (fixed N2 minus grain N). Data were then subjected to simple and multivariate regression analyses with Pfix and total N2 fixed as the dependent variables and soil nitrate, shoot N, and grain yield as the independent variables. Simple regression coefficients (r2) for Pfix were 0·26 with shoot N as the independent variable, 0·59 with soil nitrate, and 0·62 with grain yield. Coefficient values were increased in the 2-factor (multiple) regressions to 0·74 (P<0·001) for soil nitrate plus shoot N, and 0·82 (P < 0·001) for soil nitrate plus grain yield. For total N2 fixed, the regression coefficient was lower at 0·68 (P < 0·001), using soil nitrate plus grain yield. We tested the functions against an independent data set with best prediction of Pfix involving the nitrate and grain yield equation (r2 = 0·83; P < 0·001). Total N2 fixed was not well predicted. We concluded that further development of such functions is warranted to refine both accuracy and precision for chickpea and to extend the approach to other species.


1998 ◽  
Vol 49 (3) ◽  
pp. 419 ◽  
Author(s):  
J. Evans ◽  
D. P. Heenan

Procedures for assessing the quantity of symbiotically fixed nitrogen (kg N/ha) in standing crops of lupin and for estimating variation of N2 fixation by lupins in different years were determined empirically and described. In standing crops, N2 fixation was estimated from crop height, plant population density, and a bioassay of soil mineral nitrogen (cereal crop N; kg N/ha). In addition it was also estimated from rainfall, sowing date, and cereal N, which consequently enabled prediction of seasonal variation in fixed N using historical rainfall data. Procedures for estimating the potential contribution of N2 fixation to soil N, and the effects of lupin and cereal N budgets on soil N balance based on differences in fixed N and grain N (grain yield×estimated grain N concentration) are also given. The collective procedures are applied to a site in south-eastern Australia and the predicted crop effects on soil N balance compared with actual field data. Perceived limitations of the procedures are discussed.


1983 ◽  
Vol 34 (4) ◽  
pp. 391 ◽  
Author(s):  
FJ Bergersen ◽  
GL Turner

Nitrogen (N2) fixation by nodulated subterranean clover, in swards with perennial ryegrass, was studied by using the natural abundance of 15N in sward components compared with a method using artificial enrichment of the soil with small amounts of K15NO3. Significant differences between the 15N concentrations in ryegrass and clover enabled yield-independent estimates of the proportion (P) of clover nitrogen fixed from atmospheric N2. Yield-dependent estimates of P were also made during intervals of growth in autumn and in spring. Values of P increased with time and during spring were close to l00%, when maximum fixation rates were approximately 4 kg N ha-1 day-1. Consistent differences in 15N concentration of shoots and roots had little effect on P. Early in the experiment, natural enrichment gave lower estimates of P than 15NO-3 -enriched treatments. Yield-independent and yield-dependent methods gave similar estimates of P. During winter, when no net growth or nitrogen accumulation was recorded, there appeared to be loss of 15N from the plants, possibly because of loss of highly labelled plant parts, balanced by slow growth of tissue containing a lower 15N concentration. During winter, calculation of P was therefore unreliable.


1990 ◽  
Vol 30 (5) ◽  
pp. 655
Author(s):  
AL Cowie ◽  
RS Jessop ◽  
DA MacLeod ◽  
GJ Davis

The effect of increasing external nitrate (NO-3) concentration on the nodulation of Lupinus albus and L. angustifolius lines was examined in 2 sand culture experiments. In the first experiment 4 lines, 3 L. albus and 1 L. angustifolius, were grown at NO-3 concentrations of 0, 2, 8, 16, and 30 mmol/L for 49 days. Increasing the NOT concentration reduced nodule weight in all varieties to a similar extent. In a second experiment, 18 L. angustifolius lines were grown at NO-3 concentrations of 2 and 8 mmol/L for 49 days. The ratio of nodule weights at the 8 and 2 mmol/L NO-3 treatments varied widely, from 23 to 71%, between the lines. There appears to be potential for selection of L. angustifolius varieties able to maintain N2 fixation at increased levels of soil N.


2002 ◽  
Vol 53 (5) ◽  
pp. 599 ◽  
Author(s):  
J. E. Turpin ◽  
D. F. Herridge ◽  
M. J. Robertson

Soil in which nodulated legumes are growing often contains more nitrate nitrogen (N) than soil in which unnodulated legumes or non-legumes are growing. There is conjecture, however, as to whether the extra or ‘spared’ N is due to reduced use of soil N by the legume or to net mineralisation of legume root and nodular N. We report results of a field experiment to quantify and compare, at different levels of soil-N supply, N2 fixation, and soil-N use by chickpea (Cicer arietinum) and fababean (Vicia faba). Wheat (Triticum aestivum) was included as a non-N2-fixing control. Plants of the 3 species were grown on a low-nitrate Vertosol with fertiliser N rates of 0, 50, and 100 kg/ha (0N, 50N, and 100N), applied 6 weeks before sowing. Samples were collected at sowing and at 64, 100, 135, and 162 days after sowing (DAS) for analysis of soil nitrate, root, and grain dry matter (DM) and N and shoot DM, N, and 15N. The latter was used to estimate the percentage (%Ndfa) and total N fixed by the 2 legumes. Soil nitrate levels to a depth of 1.8 m at sowing were 11–17 kg N/ha (0N), 41–55 kg N/ha (50N), and 71–86 kg N/ha (100N). Grain yields of the 2 legumes were unaffected by soil-N supply (fertiliser N treatment), being 2.0–2.4 t/ha for chickpea and 3.7–4.6 t/ha for fababean. Wheat grain yields varied from 1.6 t/ha (0N) to 4.8 t/ha (100N). Fababean fixed more N than chickpea. Values (total plant including roots) were 209–275 kg/ha for fababean and 146–214 kg/ha for chickpea. Corresponding %Ndfa values were 69–88% (fababean) and 64–85% (chickpea). Early in crop growth, when soil N supply was high in the 100N treatment, fababean maintained a higher dependence on N2 fixation than chickpea (Ndfa of 45% v. 12%), fixed greater amounts of N (57 v. 16 kg/ha), and used substantially less soil N (69 v. 118 kg/ha). In this situation, soil N sparing was observed, with soil nitrate levels significantly higher in the fababean plots (P < 0.05) than under chickpea or wheat. At the end of growth season, however, there were no crop effects on soil nitrate levels. Soil N balances, which combined crop N fixed as inputs and grain N as outputs, were positive for the legumes, with ranges 80–135 kg N/ha for chickpea and 79–157 kg N/ha for fababean, and negative for wheat (–20 to –66 kg N/ha). We concluded that under the starting soil nitrate levels in this experiment, levels typical of many cropping soils in the region, high-biomass fababean and chickpea crops will not spare significant amounts of soil N. In situations of higher soil nitrate and/or smaller biomass crops with less N demand, nitrate sparing may occur, particularly with fababean.


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