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1.
Yield and nitrogen use efficiency (NUE) of wheat was investigated under field conditions using two types of irrigation waters with and without nitrogen on a sandy-loam to loamy-sand soil during 1992–1993 and 1993–1994. Depending upon different nitrogen treatments, the mean crop yield ranges in 1992–1993 were: grain yield 6.19–6.87 Mg ha− and biomass 15.41–16.34 Mg ha−1 receiving treated effluent. The mean crop yield ranges in 1993–1994 were: grain yield 0.46–3.23 Mg ha−1 (well water) and 5.20–6.54 Mg ha−1 (treated effluent); and biomass 1.84–10.80 Mg ha−1 (well water), and 16.00–19.29 Mg ha−1 (treated effluent). The NUE for grain yield in 1992–1993 was between 16.70–50.23 kg kg−1 N (well water) and 20.65–91.56 kg kg−1 N (treated effluent). Whereas the NUE in 1993-94, varied between 10.49–32.13 kg grain kg−1 N (well water) and 21.30–72.93 kg grain kg−1 N (treated effluent). The NUE for total biomass in 1992–1993 varied between 46.54–130.32 kg kg−1 N (well water) and 53.66–158.77 kg kg−1 N (treated effluent). Similarly, the NUE in 1993–1994 varied between 35.99–102.1 kg biomass kg−1 N (well water) and 59.27–161.89 kg biomass kg−1 N (treated effluent). A significant decrease in NUE was observed with increasing nitrogen application both for grain and biomass production. In conclusion, a higher grain yield and NUE of wheat crop can be achieved with low application rates of nitrogen if the crop is irrigated with treated effluent containing nitrogen in the range of 20 mg L−1 and above.  相似文献   

2.
A field experiment was carried out to determine the effect of irrigation and nitrogen on two cultivars of oilseed crops (Brassica napus L. cv. canola and Brassica campestris L. cv rapeseed) on a sandy-clay-loam soil during 1993–1994. The mean plant height ranges for canola were: 1.20–1.40 m (well water) and 1.40–1.57 m (aquaculture effluent); and for rapeseed from 1.281.52 m (well water) and 1.41–1.58 m (aquaculture effluent) in different fertilizer treatments. Mean biomass yield for canola ranged between 14.60–17.84 Mg ha−1 (well water) and 14.09–19.51 Mg ha−1 (aquaculture effluent); and for rapeseed from 16.67–19.51 Mg ha−1 (well water) and 12.70–20.74 Mg ha−1 (aquaculture effluent). The mean seed yield for canola varied from 2.65–3.44 Mg ha−1 (well water) and 3.02–3.74 Mg ha−1 (aquaculture effluent): and for rapeseed from 2.73–3.26 Mg ha−1 (well water) and from 2.62–3.29 Mg ha−1 (aquaculture effluent). The mean straw yield ranges for canola were: 12.01–14.39 Mg ha−1 (well water) and 13.65–15.93 Mg ha−1 (aquaculture effluent); and for rapeseed from 11.67–13.28 Mg ha−1 (well water) and 9.83–17.45 Mg ha−1 (aquaculture effluent). The mean oil contents for canola were 30.92–36.12% (aquaculture effluent) and 32.47–35.78% (well water); and for rapeseed from 30.15–34.53% (aquaculture effluent) and 33.50–35.96% (aquaculture effluent). The mean protein contents of straw were 5.42–6.44% (canola) and 3.78–4.37% (rapeseed) in different fertilizer treatments. Application of 175 kg N ha−1 with 50 kg P ha−1 showed significant effect on crop yield under both types of irrigation water. Based on the results of this study, it appears that cultivars of rapeseed recently introduced from Canada have an excellent potential as oilseed crops in Saudi Arabia.  相似文献   

3.
Based on a field study on the semi-arid Loess Plateau of China, the strategies of limited irrigation in farmland in dry-period of normal-precipitation years are studied, and the effects on water use and grain yield of spring wheat of dry-period irrigation and fertilizer application when sowing are examined. The study includes four treatments: (1) with 90 mm dry-period irrigation but without fertilizer application (W); (2) with fertilizer application but without dry-period irrigation (F); (3) with 90 mm dry-period irrigation plus fertilizer application (WF); (4) without dry-period irrigation and fertilizer application (CK). The results indicate that dry-period irrigation resulted in larger and deeper root systems and larger leaf area index (LAI) compared with the non-irrigated treatments. The root/shoot ratio (R/S) in the irrigated treatments was significantly higher than in the non-irrigated treatments. The grain yields in F, W and WF are 1509, 2712 and 3291 kg ha−1, respectively, which are 13.7, 104.3 and 147.9% higher than that (1328 kg ha−1) of CK, and at the same time the grain yields in W and WF are also significantly higher than in F. Water use efficiencies (WUE) in terms of grain yield are 5.70 and 6.91 kg ha−1 mm−1 in W and WF, respectively, being 65.7 and 101.1% higher than that (3.44 kg ha−1 mm−1) of CK. The highest WUE and grain yield consistently occurred in WF, suggesting that the combination of dry-period irrigation and fertilizer application has a beneficial effect on improving WUE and grain yield of spring wheat.  相似文献   

4.
A field trial on a loamy sand soil was carried out to study the effect of three irrigation waters with different qualities on growth and yield of ‘Gesto’, a barley (Hordeum vulgare L.) cultivar. Three irrigation water quality treatments (canal irrigation water, drainage water, and mixed canal and drainage waters at 1:1 ratio) were imposed with two irrigation frequencies (I and 2 week intervals). In addition, nitrogen and phosphorus fertilizers were applied at different rates. Barley grain and straw yields were significantly decreased under the use of drainage water (EC 10.7–16.7 dS m−1), attributed mainly to reduction in the number of spikes per plant and grain weight. The mixed irrigation water (EC 6.8–9.9 dS m−1) produced high seedling emergence and good vegetative growth, which was followed by high grain and straw yields. These yields were not significantly different from those under fresh canal irrigation water (EC 2.8–3.9 dS m−1). Thus, mixed water could be another alternative for irrigation under similar experimental conditions especially with high rates of nitrogen (250–350 kg ha−1) and phosphorus (90 kg ha−1) fertilization at weekly irrigation intervals, which could eventually save more fresh irrigation canal water for other cultivated crops.  相似文献   

5.
This study was conducted to determine the effect of different supplemental irrigation rates on chickpea grown under semiarid climatic conditions. Chickpea plots were irrigated with drip irrigation system and irrigation rates included the applications of 0 (I 0) 25 (I 25), 50 (I 50), 75 (I 75), 100 (I 100), and 125 % (I 125) of gravimetrically measured soil water deficit. Plant height, 1,000 seed weight, yield, biomass, and harvest index (HI) parameters were determined in addition to yield-water functions, evapotranspiration (ET), water use efficiency (WUE), and irrigation water use efficiency (IWUE). Significant differences were noted for plant height (ranging from 24.0 to 37.5 cm), 1,000 seed weight (ranging from 192.0 to 428.7 g), and aboveground biomass (ranging from 2,722 to 6,083 kg ha?1) for water applications of I 0 and I 125. Statistical analysis indicated a strong relationship between the amount of irrigation and yield, which ranged from 256.5 to 1,957.3 kg ha?1. Harvest index values ranged between 0.092 and 0.325, while WUE and IWUE values ranged between 1.15–4.55 and 1.34–8.36 (kg ha?1 mm?1), respectively.  相似文献   

6.
In the Mesilla Valley of southern New Mexico, furrow irrigation is the primary source of water for growing onions. As the demand for water increases, there will be increasing competition for this limited resource. Water management will become an essential practice used by farmers. Irrigation efficiency (IE) is an important factor into improving water management but so is economic return. Therefore, our objectives were to determine the irrigation efficiency, irrigation water use efficiency (IWUE) and water use efficiency (WUE), under sprinkler, furrow, and drip irrigated onions for different yield potential levels and to determine the IE associated with the amount of water application for a sprinkler and drip irrigation systems that had the highest economic return.Maximum IE (100%) and economic return were obtained with a sprinkler system at New Mexico State University’s Agriculture Science Center at Farmington, NM. This IE compared with the 54–80% obtained with the sprinkler irrigation used by the farmers. The IEs obtained for onion fields irrigated with subsurface drip irrigation methods ranged from 45 to 77%. The 45% represents the nonstressed treatments, in which an extra amount of irrigation above the evapotranspiration (Et) requirement was applied to keep the base of the onion plates wet. The irrigation water that was not used for Et went to deep drainage water. The return on the investment cost to install a drip system operated at a IE of 45 was 29%. Operating the drip system at a IE of 79% resulted in a yield similar to surface irrigated onions and consequently, it was not economical to install a drip system. The IEs at the furrow-irrigated onion fields ranged from 79 to 82%. However, the IEs at the furrow-irrigated onion fields were high because farmers have limited water resources. Consequently, they used the concept of deficit irrigation to irrigate their onion crops, resulting in lower yields. The maximum IWUE (0.084 t ha−1 mm−1 of water applied) was obtained using the sprinkler system, in which water applied to the field was limited to the amount needed to replace the onions’ Et requirements. The maximum IWUE values for onions using the subsurface drip was 0.059 and 0.046 t ha−1 mm−1 of water applied for furrow-irrigated onions. The lower IWUE values obtained under subsurface drip and furrow irrigation systems compared with sprinkler irrigation was due to excessive irrigation under subsurface drip and higher evaporation rates from fields using furrow irrigation. The maximum WUE for onions was 0.009 t ha−1 mm−1 of Et. In addition, WUE values are reduced by allowing the onions to suffer from water stress.  相似文献   

7.
A 2-year experiment was conducted at Tal Amara Research Station in the Bekaa Valley of Lebanon to determine water use and lint yield response to the length of irrigation season of drip irrigated cotton (Gossypium hirsutum L.). Crop evapotranspiration (ETcrop) and reference evapotranspiration (ETrye-grass) were directly measured at weekly basis during the 2001 growing period using crop and rye-grass drainage lysimeters. Crop coefficients (Kc) in the different growth stages were calculated as ETcrop/ETrye-grass. Then, the calculated Kc values were used in the 2002 growing period to estimate evapotranspiration of cotton using the FAO method by multiplying the calculated Kc values by ETrye-grass measured in 2002. The length of irrigation season was determined by terminating irrigation permanently at first open boll (S1), at early boll loading (S2), and at mid boll loading (S3). The three treatments were compared to a well-watered control (C) throughout the growing period. Lint yield was defined as a function of components including plant height at harvest, number of bolls per plant, and percentage of opened bolls per plant.Lysimeter-measured crop evapotranspiration (ETcrop) totaled 642 mm in 2001 for a total growing period of 134 days, while when estimated with the FAO method in 2002 it averaged 669 mm for a total growing period of 141 days from sowing to mature bolls. Average Kc values varied from 0.58 at initial growth stages (sowing to squaring), to 1.10 at mid growth stages (first bloom to first open boll), and 0.83 at late growth stages (early boll loading to mature bolls).Results showed that cotton lint yields were reduced as irrigation amounts increased. Average across years, the S1 treatment produced the highest yield of 639 kg ha−1 from total irrigations of 549 mm, compared to the S2 and S3 treatments, which yielded 577 and 547 kg ha−1 from total irrigations of 633 and 692 mm, respectively, while the control resulted in 457 kg ha−1 of lint yield from 738 mm of irrigation water. Water use efficiency (WUE) was found to be higher in S1 treatment and averaged 1.3 kg ha−1 mm−1, followed by S2 (1.1 kg ha−1 mm−1), and S3 (1.0 kg ha−1 mm−1), while in the control WUE was 0.80 kg ha−1 mm−1. Lint yield was negatively correlated with plant height and the number of bolls per plant and positively correlated with the percentage of opened bolls. This study suggests that terminating irrigation at first open boll stage has been found to provide the highest cotton yield with maximum WUE under the semi-arid conditions of the Bekaa Valley of Lebanon.  相似文献   

8.
A study was conducted to determine the effects of different drip irrigation regimes on yield and yield components of cucumber (Cucumbis sativus L.) and to determine a threshold value for crop water stress index (CWSI) based on irrigation programming. Four different irrigation treatments as 50 (T-50), 75 (T-75), 100 (T-100) and 125% (T-125) of irrigation water applied/cumulative pan evaporation (IW/CPE) ratio with 3-day-period were studied.Seasonal crop evapotranspiration (ETc) values were 633, 740, 815 and 903 mm in the 1st year and were 679, 777, 875 and 990 mm in the 2nd year for T-50, T-75, T-100 and T-125, respectively. Seasonal irrigation water amounts were 542, 677, 813 and 949 mm in 2002 and 576, 725, 875 and 1025 mm in 2003, respectively. Maximum marketable fruit yield was from T-100 treatment with 76.65 t ha−1 in 2002 and 68.13 t ha−1 in 2003. Fruit yield was reduced significantly, as irrigation rate was decreased. The water use efficiency (WUE) ranged from 7.37 to 9.40 kg m−3 and 6.32 to 7.79 kg m−3 in 2002 and 2003, respectively, while irrigation water use efficiencies (IWUE) were between 7.02 and 9.93 kg m−3 in 2002 and between 6.11 and 8.82 kg m−3 in 2003.When the irrigation rate was decreased, crop transpiration rate decreased as well resulting in increased crop canopy temperatures and CWSI values and resulted in reduced yield. The results indicated that a seasonal mean CWSI value of 0.20 would result in decreased yield. Therefore, a CWSI = 0.20 could be taken as a threshold value to start irrigation for cucumber grown in open field under semi-arid conditions.Results of this study demonstrate that 1.00 IW/CPE water applications by a drip system in a 3-day irrigation frequency would be optimal for growth in semiarid regions.  相似文献   

9.
Field experiments were conducted for 2 years to investigate the effects of various levels of nitrogen (N) and methods of cotton planting on yield, agronomic efficiency of N (AEN) and water use efficiency (WUE) in cotton irrigated through surface drip irrigation at Bathinda situated in semi-arid region of northwest India. Three levels of N (100, 75 and 50% of recommended N, 75 kg ha−1) were tested under drip irrigation in comparison to 75 kg of N ha−1 in check-basin. The three methods of planting tried were; normal sowing of cotton with row to row spacing of 67.5 cm (NS), normal paired row sowing with row to row spacing of 35 and 100 cm alternately (NP) and dense paired row sowing with row to row spacing of 35 and 55 cm alternately resulting in total number rows and plants to be 1.5 times (DP) than NS and NP. In NS there was one lateral along each row, but in paired sowings there was one lateral between each pair of rows. Consequently the number of laterals and quantity of water applied was 50 and 75% in NP and DP, respectively, as compared with NS in which irrigation water applied was equivalent to check-basin.Drip irrigation under NS resulted in an increase of 258 and 453 kg ha−1 seed cotton yield than check-basin during first and second year, respectively, when same quantity of water and N was applied. Drip irrigation under dense paired sowing (DP) in which the quantity of irrigation water applied was 75% as compared with NS, further increased the yield by 84 and 101 kg ha−1 than NS during first and second year, respectively. Drip irrigation under NP, in which the quantity of water applied and number of laterals used were 50% as compared with drip under NS, resulted in a reduction in seed cotton yield of 257 and 112 kg ha−1 than NS during first and second year, respectively. However, the yield obtained in NP under drip irrigation was equivalent to yield obtained in NS under check-basin during first year but 341 kg ha−1 higher yield was obtained during second year. The decrease in N applied, irrespective of methods of planting, caused a significant decline in seed cotton yield during both the years. Water use efficiency (WUE) under drip irrigation increased from 1.648 to 1.847 and from 0.983 to 1.615 kg ha−1 mm−1 during first and second year, respectively, when the same quantity of N and water was applied. The WUE further increased to 2.125 and 1.788 kg ha−1 mm−1 under DP during first and second year, respectively. The agronomic efficiency of nitrogen was higher in drip than check-basin during both the years when equal N was applied. The WUE decreased with decrease in the rate of N applied under fertigation but reverse was true for AEN. It is evident that DP under drip irrigation resulted in higher seed cotton yield, WUE and AEN than NS and also saved 25% irrigation water as well as cost of laterals.  相似文献   

10.
A field study was conducted at North Platte, Nebraska in 2007–2009, imposing eight irrigation treatments, ranging from dryland to fully irrigated. Four of the eight treatments allowed for various degrees of water stress only after tasseling and silking. In 2007, corn yield ranged from 8.9 Mg ha?1 with a season total of 41 mm of irrigation water to 11.5 Mg ha?1 for the fully irrigated treatment (264 mm of irrigation water). The treatment with the greatest reduction in irrigation water after tasseling and silking (158 mm) had a mean yield of 10.9 Mg ha?1, only 0.6 Mg ha?1 less than the fully irrigated treatment. In 2009, yields ranged from 12.6 to 13.5 Mg ha?1. There were no significant yield differences between the irrigation treatments for several possible reasons: more in-season precipitation and cooler weather required less irrigation water; much of the irrigation water was applied after the most water-stress sensitive stages of tasseling and silking; and lower atmospheric demand allowed for soil water contents well below 50 % management allowed depletion (MAD) not to cause any yield losses.  相似文献   

11.
Rainfed crop production in northern China is constrained by low and variable rainfall, and by improper management practices. This study explored both the impact of long-term rainfall variability and the long-term effects of various combinations of maize stover, cattle manure and mineral fertiliser (NP) applications on maize (Zea mays L.) yields and water use efficiency (WUE) under reduced tillage practices, at Shouyang Dryland Farming Experimental Station in northern China from 1993 onwards. The experiment was set up according to an incomplete, optimal design, with 3 factors at five levels and 12 treatments including a control with two replications. Grain yields were greatly influenced by the amount of rain during the growing season, and by soil water at sowing. Annual mean grain yields ranged from 3 to 10 t ha−1 and treatment mean yields from 4.2 to 7.2 t ha−1. The WUE ranged from 40 in treatments with balanced nutrient inputs in dry (weather/or soil) years to 6.5 kg ha−1 mm−1 for the control treatments in wet years. The WUE averaged over the 15-year period ranged from 11 to 19 kg ha−1 mm−1. Balanced combination of stover (3000-6000 kg), manure (1500-6000 kg) and N fertiliser (105 kg) gave the highest yield and hence WUE. It is suggested that 100 kg N per ha should be a best choice, to be adapted according to availability of stover and manure. Possible management options under variable rainfall conditions to alleviate occurring moisture stress for crops must be tailored to the rainfall pattern. The potentials of split applications, targeted to the need of the growing crop (response nutrient management), should be explored to further improve grain yield and WUE.  相似文献   

12.
Field experiments were carried out in the 2004 and 2005 growing seasons on drip irrigated dwarf green beans (Phaseolus vulgaris, humilis). Soil water content (SWC), spectral reflectance and yield were monitored. Based on these data crop evapotranspiration (ETc), soil water deficit index (SWDI), water use efficiency (WUE) and four separate spectral indexes were calculated. In order to determine use opportunities of spectral indexes for estimation of yield, SWDI and WUE, some statistical analyzes were made. Results showed that spectral indexes could be used for monitoring of yield, SWDI and WUE. Especially, Soil Adjusted Vegetation Index (SAVI) had the highest correlations with all three of the parameters. The estimation procedure which was given in this study has a potential use either during, or at the end of the growing season. Estimated values of WUE and SWDI were 3.2 (kg m?3) and 0.12, respectively, through SAVI and the given procedure, indicates the optimal water use and yield conditions for dwarf green beans. At this situation, probably ETc was 580 mm and yield was 25.5 t ha?1.  相似文献   

13.
The potato (Solanum tuberosum L.) is widely planted in the Middle Anatolian Region, especially in the Nigde-Nevsehir district where 25% of the total potato growing area is located and produces 44% of the total yield. In recent years, the farmers in the Nigde-Nevsehir district have been applying high amounts of nitrogen (N) fertilizers (sometimes more than 900 kg N ha−1) and frequent irrigation at high rates in order to get a much higher yield. This situation results in increased irrigation and fertilization costs as well as polluted ground water resources and soil. Thus, it is critical to know the water and nitrogen requirements of the crop, as well as how to improve irrigation efficiency. Field experiments were conducted in the Nigde-Nevsehir (arid) region on a Fluvents (Entisols) soil to determine water and nitrogen requirements of potato crops under sprinkler and trickle irrigation methods. Irrigation treatments were based on Class A pan evaporation and nitrogen levels were formed with different nitrogen concentrations.The highest yield, averaging 47,505 kg ha−1, was measured in sprinkler-irrigated plots at the 60 g m−3 nitrogen concentration level in the irrigation treatment with limited irrigation (480 mm). Statistically higher tuber yields were obtained at the 45 and 60 g m−3 nitrogen concentration levels in irrigation treatments with full and limited irrigation. Maximum yields were obtained with about 17% less water in the sprinkler method as compared to the trickle method (not statistically significant). On the loam and sandy loam soils, tuber yields were reduced by deficit irrigation corresponding to 70% and 74% of evapotranspiration in sprinkler and trickle irrigations, respectively. Water use of the potato crop ranged from 490 to 760 mm for sprinkler-irrigated plots and 565–830 mm for trickle-irrigated treatments. The highest water use efficiency (WUE) levels of 7.37 and 4.79 kg m−3 were obtained in sprinkle and trickle irrigated plots, respectively. There were inverse effects of irrigation and nitrogen levels on the WUE of the potato crops. Significant linear relationships were found between tuber yield and water use for both irrigation methods. Yield response factors were calculated at 1.05 for sprinkler methods and 0.68 for trickle methods. There were statistically significant linear and polynomial relationships between tuber yield and nitrogen amounts used in trickle and sprinkler-irrigated treatments, respectively. In sprinkler-irrigated treatments, the maximum tuber yield was obtained with 199 kg N ha−1. The tuber cumulative nitrogen use efficiency (NUEcu) and incremental nitrogen use efficiency (NUEin) were affected quite differently by water, nitrogen levels and years. NUEcu varied from 16 to 472 g kg−1 and NUEin varied from 75 to 1035 g kg−1 depending on the irrigation method. In both years, the NH4-N concentrations were lower than NO3-N, and thus the removed nitrogen and nitrogen losses were found to be 19–87 kg ha−1 for sprinkler methods and 25–89 kg ha−1 for trickle methods. Nitrogen losses in sprinkler methods reached 76%, which were higher than losses in trickle methods.  相似文献   

14.
Summary A field trial was conducted to determine the response of rapeseed (Brassica napus cv. Marnoo) to two irrigation treatments and six nitrogen fertilizer treatments. Response to nitrogen was greater with than without irrigation. Oil content was increased with irrigation but decreased under increasing nitrogen application, and was inversely related to seed nitrogen concentration. Oil yields averaged 1,168 kg ha–1 under irrigated treatments compared with 835 kg ha–1 under rainfed treatments. Maximum oil yield (approx. 1,557 kg ha–1) was obtained from the irrigated treatment fertilized with 100 kg N ha–1 applied at sowing.  相似文献   

15.
《Agricultural Systems》2004,82(1):45-56
Understanding processes of maize (Zea mays L.) growth and production of grain in high-yielding, irrigated conditions offers hope to understand yield potential in many other environments. In this study we investigated such processes at the plant level, and attempted to simulate maize yields at the field level and county level in the high yielding region of the High Plains of Texas. In addition, we used the normalized difference vegetation index (NDVI) from satellite data of year 2000 to update leaf area index for yield simulation in three counties. In the field study, we measured maize leaf area index (LAI), the fraction of photosynthetically active radiation intercepted (FIPAR), and the harvest index (HI) in irrigated plots near Dumas, Texas. The light extinction coefficient (k) for Beer's law was calculated with the FIPAR and the LAI. The radiation use efficiency (RUE) was determined with sequential measurements of the fraction of photosynthetically active radiation (PAR) intercepted and biomass harvests. The RUE was 3.98 g of above-ground biomass per MJ of intercepted PAR in 1999 and 3.41 in 2000 for three sampling dates prior to silking. These values are 106 and 93% of the expected RUE values at the measured vapor pressure deficits, using a previously published response function. The mean k value was −0.46 in 1999 and −0.47 in 2000, similar to the expected value of −0.43 reported in the literature for this row spacing. The mean HI measured in 2000 was 0.52, similar to values of 0.53 and 0.54 in the literature. Application of these parameters to maize simulation with the Agriculture Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) model for 13 center pivot irrigated fields near Dumas in 1999 provided simulations within 1.0 Mg ha−1 with a mean error of 0.03 Mg ha−1 and a mean square error of 0.10. For five years of grain yields reported for each of four counties in this region of Texas, ALMANAC simulations were within 5% of the mean measured yields. Introduction of PAR interception, based on the satellite-derived normalized difference vegetation index (NDVI), into ALMANAC resulted in slight increases in accuracy of yield prediction for two counties and a slight decrease in accuracy in one county for year 2000. Consistency in values of RUE, k, and HI in this study as compared with values reported in the literature will aid modelers simulating maize growth and grain yields in similar high-yielding, irrigated conditions.  相似文献   

16.
Yields of dryland crops are governed by the moisture in the soil profile at seeding and by rainfall during the growing season. Occasionally limited amounts of water may also be available for irrigation. Field experiments were conducted over a period of 4 years on loamy sand and 3 years on sandy loam to study the effects of pre-seeding, post-seeding and split application of limited amounts of water on root growth, water use, dry matter accumulation and grain yield of wheat. This article reports the treatment effects on dry matter accumulation and grain yield.Early season water stress decreased the rate of dry matter accumulation. Grain yield responded significantly to irrigation 30 days after seeding irrespective of the amount of water, year and soil type. Yield with post-seeding irrigation averaged 3518 kg ha?1 against 2317 kg ha?1 for unirrigated control in loamy sand and 4440 kg ha?1 against 3391 kg ha?1 in sandy loam. The increase in yield was manifested by a significant increase in the number of effective tillers per m row length, number of grains per ear and thousand grain weight.  相似文献   

17.
The wheat- (Triticum aestivum L.) and corn- (Zea mays L.) rotation system is important for food security in Northwest China. Grain yield and water-use efficiency [WUE: grain yield/estimated evapotranspiration (ET)] were recorded during a 24-year fertilization trial in Pingliang (Gansu, China). Mean yields of wheat for the 16 years, starting in 1981, ranged from 1.29 Mg ha−1 for unfertilized plots (CK) to 4.71 Mg ha−1 for plots that received manure (M) annually with nitrogen (N) and phosphorus (P) fertilizers (MNP). Corn yields for the 6 years, starting in 1979, averaged 2.29 and 5.61 Mg ha−1 for the same respective treatments. Whether the years were dry, normal or wet, average grain yields and WUEs for both crops were consistently highest in the MNP and lowest in the CK treatment, and were always lower in the N than in the M treatment and in all others treatments that received N along with P fertilizers. More importantly, WUEs for MNP and for straw along with N annually and P every second year (SNP) were always higher than the other fertilized treatments in dry years. Compared to yield data, coefficients of variance (CV) for WUEs were consistently low for all treatments, suggesting that WUEs were relatively stable from year to year. Yields and WUEs declined over time, except in the CK and MNP treatments for wheat. Declined yields of wheat for the N and M treatments were comparable, and the decline for the NP treatment was similar to that for the SNP treatment. Likewise, corn yields and WUEs declined for all treatments. Grain yields were significantly correlated with ET, with slopes ranging from 0.5 to 1.27 kg m−3 for wheat and from 1.15 to 2.03 kg m−3 for corn. Balanced fertilization and long-term addition of organic material to soil should be encouraged in this region to maximize the use of stored soil water, arrest grain yields decline, and ensure sustainable productivity using this intensive cereal cropping system.  相似文献   

18.
Wheat (Triticum durum L.) yields in the semi-arid regions are limited by inadequate water supply late in the cropping season. Planning suitable irrigation strategy and nitrogen fertilization with the appropriate crop phenology will produce optimum grain yields. A 3-year experiment was conducted on deep, fairly drained clay soil, at Tal Amara Research Station in the central Bekaa Valley of Lebanon to investigate the response of durum wheat to supplemental irrigation (IRR) and nitrogen rate (NR). Three water supply levels (rainfed and two treatments irrigated at half and full soil water deficit) were coupled with three N fertilization rates (100, 150 and 200 kg N ha−1) and two cultivars (Waha and Haurani) under the same cropping practices (sowing date, seeding rate, row space and seeding depth). Averaged across N treatments and years, rainfed treatment yielded 3.49 Mg ha−1 and it was 25% and 28% less than half and full irrigation treatments, respectively, for Waha, while for Haurani the rainfed treatment yielded 3.21 Mg ha−1, and it was 18% and 22% less than half and full irrigation, respectively. On the other hand, N fertilization of 150 and 200 kg N ha−1 increased grain yield in Waha by 12% and 16%, respectively, in comparison with N fertilization of 100 kg N ha−1, while for cultivar Haurani the increases were 24% and 38%, respectively. Regardless of cultivar, results showed that supplemental irrigation significantly increased grain number per square meter and grain weight with respect to the rainfed treatment, while nitrogen fertilization was observed to have significant effects only on grain number per square meter. Moreover, results showed that grain yield for cultivar Haurani was less affected by supplemental irrigation and more affected by nitrogen fertilization than cultivar Waha in all years. However, cultivar effects were of lower magnitude compared with those of irrigation and nitrogen. We conclude that optimum yield was produced for both cultivars at 50% of soil water deficit as supplemental irrigation and N rate of 150 kg N ha−1. However, Harvest index (HI) and water use efficiency (WUE) in both cultivars were not significantly affected neither by supplemental irrigation nor by nitrogen rate. Evapotranspiration (ET) of rainfed wheat ranged from 300 to 400 mm, while irrigated wheat had seasonal ET ranging from 450 to 650 mm. On the other hand, irrigation treatments significantly affected ET after normalizing for vapor pressure deficit (ET/VPD) during the growing season. Supplemental irrigation at 50% and 100% of soil water deficit had approximately 26 and 52 mm mbar−1 more ET/VPD, respectively, than those grown under rainfed conditions.  相似文献   

19.
With decreasing water availability for agriculture and increasing demand for rice, water use in rice production systems has to be reduced and water productivity increased. Alternately submerged–nonsubmerged (ASNS) systems save water compared with continuous submergence (CS). However, the reported effect on yield varies widely and detailed characterizations of the hydrological conditions of ASNS experiments are often lacking so that generalizations are difficult to make. We compared the effects of ASNS and CS on crop performance and water use, at different levels of N input, in field experiments in China and the Philippines, while recording in detail the hydrological dynamics during the experiment. The experiments were conducted in irrigated lowlands and followed ASNS practices as recommended to farmers in China. The sites had silty clay loam soils, shallow groundwater tables and percolation rates of 1–4.5 mm per day.Grain yields were 4.1–5.0 t ha−1 with 0 kg N ha−1 and 6.8–9.2 t ha−1 with 180 kg N ha−1. Biomass and yield did not significantly differ between ASNS and CS, but water productivity was significantly higher under ASNS than under CS in two out of three experiments. There was no significant water×N interaction on yield, biomass, and water productivity. Combined rainfall plus irrigation water inputs were 600–960 mm under CS, and 6–14% lower under ASNS. Irrigation water input was 15–18% lower under ASNS than under CS, but only significantly so in one experiment. Under ASNS, the soils had no ponded water for 40–60% of the total time of crop growth. During the nonsubmerged periods, ponded water depths or shallow groundwater tables never went deeper than −35 cm and remained most of the time within the rooted depth of the soil. Soil water potentials did not drop below −10 kPa. We argue that our results are typical for poorly-drained irrigated lowlands in Asia, and that ASNS can reduce water use up to 15% without affecting yield when the shallow groundwater stays within about 0–30 cm. A hydrological characterization and mapping of Asia’s rice area is needed to assess the extent and magnitude of potential water savings.  相似文献   

20.
During 3 consecutive years (1991–1993) a field experiment was conducted in an intensively irrigated agricultural soil in SW Spain. The main objective of this study was to determine the water flow and nitrate (N03) leaching, below the root zone, under an irrigated maize crop and after the growing season (bare soil and rainy period). The experiment was carried out on a furrow-irrigated maize crop at two different nitrogen (N)-fertilization rates, one the highest traditionally used by farmers in the region (about 500 kg N ha−1 per year) and the other one-third of the former (170 kg N ha−1 per year). The aim was to obtain data that could be used to propose modifications in N-fertilization to maintain crop yield and to prevent the degradation of the environment. The terms for water balance (crop evapotranspiration, drainage and soil water storage) and nitrate leaching were determined by intensive field monitoring of the soil water content, soil water potential and extraction of the soil solution by a combination of neutron probe, tensiometers and ceramic suction cups. Nitrogen uptake by the plant and N03-N produced by mineralization were also determined.The results showed that, in terms of water balance, crop evapotranspiration was similar at both N-fertilization rates used. During the irrigation period, drainage below the root zone was limited. Only in 1992 did the occurrence of rainfall during the early growing period, when the soil was wet from previous irrigation, cause considerable drainage. Nitrate leaching during the whole experimental period amounted to 150 and 43 kg ha−1 in the treatments with high and low N-fertilization, respectively. This occurred mainly during the bare soil and rainy periods, except in 1992 when considerable nitrate leaching was observed during the crop season due to the high drainage. Nitrate leaching was not so high during the bare soil period as might have been expected because of the brought during the experimental period. A reduction of N-fertilization thus strongly decreased nitrate leaching without decreasing yield.  相似文献   

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