Cultivar and Environmental Variation of β-glucan Content in Chinese Barleys

β-glucan is a polysaccharide compound closely related to the quality of barley used as malting,feed and food. Low β-glucan content is expected for brewing and feed barley, while high β-glucan content is desirable for food barley. The β-glucan content of barley genotypes collected from various areas of China as well as from Canada and Australia were assayed. Meanwhile a multi-locations trial was conducted to determineβ-glucan content of 10 barley cultivars in 8 locations for two successive planting years. The results showed that barley genotypes from Tibet and Xinjiang had higher β-glucan content and the genotypes with higher than 8%of β-glucan content were detected in Tibet barleys, being valuable for use in the development of healthy food.Barley cultivars being planted now in winter-sowing areas of China had basically the same β-glucan content as those from Canada and Australia. Barley seeds produced in Hangzhou had lower β-glucan content than seeds from the original areas. There was a highly significant difference in β-glucan content among 10 barleys, 8locations and between years. On an average of two years, Xiumei 3 and Kongpei 1 had the highest and lowestβ-glucan content, respectively, and Taian and Hangzhou produced the highest and lowest β-glucan content barley seeds, respectively. Analysis of AMMI model showed that interaction effect between cultivar and environment was highly significant in both experimental years, and was dependent on cuitivar, suggesting that it is important to plant the suitable cultivars in a particular area in order to obtain barley seeds with reasonableβ-glucan content.     

The influence of drought stress on malt quality traits of the wild and cultivated barleys

As a major abiotic stress, drought causes instability and deterioration of malt barley quality. There is distinct difference among barley cultivars in the responses of the main malt quality traits to drought stress. In the previous study, we identified some Tibetan wild barley accessions with relatively less change of malt quality traits under drought. In this study, we examined the impact of drought stress during grain filling stage on grain weight and several important malt quality traits, including total protein content, β-glucan content, limit dextrinase activity, β-amylase activity, and protein fractions in four barley genotypes(two Tibetan wild accessions and two cultivars). Drought treatment reduced grain weight, β-glucan content, and increased total protein content, β-amylase activity. These changes differed among barley genotypes and treatments, and are closely associated with grain filling process and kernel weight. All the results indicated Tibetan wild barley had great potential for developing drought tolerant barley cultivars. Relatively stable kernel weight or filling process under water stress should be highlighted in malt barley breeding in order to reduce the effect of water stress on malt barley quality.     

The effects of sowing date on cottonseed properties at different fruiting-branch positions

A two-year field experiment was conducted to illustrate the effects of sowing date on cottonseed properties at different fruiting-branch positions(FBPs).Two cotton cultivars(Kemian 1 and Sumian 15)were sowed on 25 April,25 May,and10 June in 2010 and 2011,respectively.The boll maturation period increased with the delaying of sowing date.Normal sowing treatment(25 April)had higher seed weight,embryo weight,embryo oil content and protein content than late sowing treatments(25 May and 10 June).The flowering date,seed weight,embryo weight,embryo oil and protein contents,and the dynamic changes of embryo oil and protein contents were altered by different FBPs.A significant interaction of sowing date×FBP was observed on embryo weight,embryo oil content,embryo protein content and the dynamic changes of embryo oil and protein contents,but was not observed on seed weight.Seed weight,embryo weight,embryo oil and protein content had significant positive correlations with the mean daily temperature(MDT),mean daily maximum temperature(MDTmax),mean daily minimum temperature(MDTmin),and mean daily solar radiation(MDSR),indicating that temperature and light resources were the main reasons for different sowing dates affecting the cottonseed properties at different FBPs.Moreover,the difference in MDT was the main difference in climatic factors among different sowing dates.     

Cultivar and Environmental Effects on β-glucanase Activity in Both Barley Grain and Malt and Its Function in β-glucan Degradation

Eight two-rowed barley cultivars were grown at seven locations in the southern winter-barleyzone of China. Mean grain β-glucanase activity ranged from 39.89 U kg-1 for Suyin2 to 49.75 U kg-1 for Xi-umai3 in 8 cultivars grown at 7 locations, and from 38.74 U kg-1 in Zhengzhou to 57. 96 U kg-1 in Putianamong 7 locations on an average of all cultivars. Correspondingly, mean malt β-glucanase activity of 8 culti-vars ranged from 313.33 U kg-1 for ZAU3 to 489.89 U kg-1 for Daner Barley, and of 7 locations from 330.40U kg-1 in Yancheng to 418.24 U kg-1 in Putian. There were significant differences among cultivars and loca-tions in malt β-glucanase activities. The locations showed much larger variation in malt β-glucanase activitiesthan cultivars. The reduction of total β-glucan content after malting varied in both cultivars and locations,with a mean of 78.31%. The analysis of correlations showed that malt β-glucan content was significantly posi-tively and negatively correlated with grain β-glucan content and malt β-glucanase activity, respectively, andmalt β-glucanase activity was significantly positively correlated with grain β-glucanase activity.     

Optimization of sowing date and seeding rate for high winter wheat yield based on pre-winter plant development and soil water usage in the Loess Plateau,China

Sowing date and seeding rate are critical for productivity of winter wheat(Triticum aestivum L.).A three-year field experiment was conducted with three sowing dates(20 September(SD1),1 October(SD2),and 10 October(SD3)) and three seeding rates(SR67.5,SR90,and SR112.5) to determine suitable sowing date and seeding rate for high wheat yield.A large seasonal variation in accumulated temperature from sowing to winter dormancy was observed among three growing seasons.Suitable sowing dates for strong seedlings before winter varied with the seasons,that was SD2 in 2012–2013,SD3 in 2013–2014,and SD2 as well as SD1 in 2014–2015.Seasonal variation in precipitation during summer fallow also had substantial effects on soil water storage,and consequently influenced grain yield through soil water consumption from winter dormancy to maturity stages.Lower consumption of soil water from winter dormancy to booting stages could make more water available for productive growth from anthesis to maturity stages,leading to higher grain yield.SD2 combined with SR90 had the lowest soil water consumption from winter dormancy to booting stages in 2012–2013 and 2014–2015; while in 2013–2014,it was close to that with SR67.5 or SR112.5.For productive growth from anthesis to maturity stages,SD2 with SR90 had the highest soil water consumption in all three seasons.The highest water consumption in the productive growth period resulted in the best grain yield in both low and high rainfall years.Ear number largely contributed to the seasonal variation in grain yield,while grain number per ear and 1 000-grain weight also contributed to grain yield,especially when soil water storage was high.Our results indicate that sowing date and seeding rate affect grain yield through seedling development before winter and also affect soil water consumption in different growth periods.By selecting the suitable sowing date(1 October) in combination with the proper seeding rate of 90 kg ha–1,the best yield was achieved.Based on these results,we recommend that the current sowing date be delayed from 22 or 23 September to 1 October.     

Effects of Nitrogen Application on Chlorophyll Fluorescence Parameters and Leaf Gas Exchange in Naked Oat

Naked oat（Avena nuda L.） was originated from China,where soil nitrogen（N） is low availability.The responses of chlorophyll（Chl.） fluorescence parameters and leaf gas exchange to N application were analysed in this study.After the N application rate ranged from 60 to 120 kg ha-1,variable fluorescence（F v）,the maximal fluorescence（F m）,the maximal photochemical efficiency（F v /F m）,quantum yield（Φ PS II） of the photosynthetic system II（PS II）,electron transport rate（ETR）,and photochemical quenching coefficient（qP） increased with N application level,however,non-photochemical quenching coefficient（qN） decreased.Moreover,there was no difference in initial fluorescence（F o） with further more N enhancement.The maximum net photosynthetic rate（P max）,apparent dark respiration rate（R d） and light saturation point（LSP） were improved with 40-56 kg N ha-1as basal fertilizer and 24-40 kg N ha-1as top dressing fertilizer applied at jointing stage.Initial quantum yield（α） was decreased with 24 kg N ha-1as basal fertilizer and 56 kg N ha-1as top dressing fertilizer.Flag-leaf net photosynthetic rate（P n） was significantly enhanced at the jointing and heading stages with 40-56 kg N ha-1as basal fertilizer; in addition,increased at grain filling stage of naked oat with 40-56 kg N ha-1as top dressing fertilizer.90 kg N ha-1（50-70% as basal fertilizer and 30-50% as top dressing fertilizer） application is recommended to alleviate photodamage of photosystem and improve the photosynthetic rate in naked oat.     

Top-dressing nitrogen fertilizer rate contributes to decrease culm physical strength by reducing structural carbohydrate content in japonica rice

Lodging is an important factor limiting rice yield and quality by bending or breaking stem in japonica rice(Oryza sativa L.) production. The objectives of this study were to determine the mechanism of lodging resistance in japonica rice as affected by carbohydrate components, especially its related arrangement in culm tissue and response to top-dressing nitrogen(N) fertilizer. Field experiments were conducted in Danyang County, Jiangsu Province, China, by using two japonica rice varieties Wuyunjing 23(lodging-resistance variety) and W3668(lodging-susceptible variety) with three top-dressing N fertilizer rates(0, 135 and 270 kg N ha~(–1)) in 2013 and 2014. Lodging related physical parameters, morphological characteristics and stem carbohydrate components were investigated at 30 d after full heading stage. Results showed that with increasing N fertilizer rates, the lodging rate and lodging index increased rapidly primarily due to significant reduction of breaking strength in two japonica rice varieties. Correlation analysis revealed that breaking strength was significantly and positively correlated with bending stress, but negatively correlated with section modulus, except for significant correlation at W3668 in 2014. Higher stem plumpness status and structural carbohydrate contents significantly enhanced stem stiffness, despite of lower non-structural carbohydrate. With higher N fertilizer rate, the culm wall thickness was almost identical, and culm diameter increased slightly. The structural carbohydrates, especially for lignin content in culm, reduced significantly under high N rate. Further histochemical staining analysis revealed that high N treatments decreased the lignin deposition rapidly in the sclerenchyma cells of mechanical tissue, large vascular bundle and small vascular bundle region, which were consistent with reduction of bending stress, especially for W3668 and thus, resulted in poor stem strength and higher lodging index. These results suggested that structural carbohydrate plays a vital role for improving stem strength in japonica rice. N rate decreased lodging resistance primarily due to poor stem stiffness, by reducing structural carbohydrate content and lignin deposition in the secondary cell wall of lower internode culm tissue.     

The Differences of Physiological Characteristics and Yield of Northern Japonica Rice in Different Nitrogen Application Patterns

The research performed analysis on differences of physiological property and yield of Tiejing No. 11 by different nitrogen fertilization patterns. The results indicated that while the nitrogen of basal: tillering: panicle was 6 ∶3∶1, the higher amount of nitrogen improved the chlorophyll content, photosynthetic capacity, effective panicle, grain weight and yield; the medium nitrogen level had advantage under the ratio 4:3:3; nitrogen application at lategrowth stage was suitable for low or medium nitrogen level,which could increase photosynthetic capacity and optimize the yield components and increase yield; under the same ratio for basic tiller and ear fertilizer, the increase of nitrogen could improve total nitrogen uptake and protein content, decrease nitrogen physiological efficiency and milled rice and tasting, but nitrogen recovery and harvest index changes had difference; as application at late growth stage in same nitrogen rate, total nitrogen uptake and protein content increased, nitrogen physiological efficiency and milled rice and amylose content and tasting decreased, nitrogen recovery and harvest index increased under low or medium nitrogen level and decreased under high nitrogen level. Nitrogen application 210 kg/hm~2 and the ratio 4 ∶3 ∶3 of basal:tillering: panicle made the yield increase by 2.8%-11.3%, and this is the optimal mode of nitrogen fertilizer application.     

Effects of Waterlogging in Different Growth Stages on the Photosynthesis,Growth, Yield,and Protein Content of Three Wheat Cultivars in Jianghan Plain

To maintain high wheat grain yield in areas where frequent and periodic waterlogging occurs, the effects of waterlog-ging on the photosynthesis, growth, yield, and protein content of three wheat cultivars, namely Xiangmai55 (X55), Jingmai102 (J102), and Zhengmai9023 (Z9023), in four different growth stages were investigated. Experiments were conducted in special y designed experimental tanks in the middle and lower reaches of the Yangtze River during the 2012-2013 and 2013-2014 wheat growing seasons in China. Results showed that X55 was the most susceptible to waterlogging, fol owed by J102 and Z9023. Chlorophyl content reduction and leaf senescence, which resulted in decreased green-to-total leaf number ratio, were induced to the greatest extents by waterlogging in booting and flowering stages, fol owed by milky stage. Meanwhile, chlorophyl content in flag leaf, plant height were significantly decreased by waterlogging in jointing stage but effectively recovered after waterlogging withdrawal, and recovery ability varied among the cultivars. Plant biomass and grain yield were most significantly decreased by waterlogging in booting and flowering stages, fol owed by milky and jointing stages. Grain protein content was also considerably affected by waterlogging depending on growth stage and cultivars. The decreased grain yield caused by waterlogging was mostly due to the sharp decline in 1 000-grain mass. Waterlogging led to reduced protein yield in al growth stages in three wheat cul-tivars. Above al , in this experiment, waterlogging decreased grain yield significantly, and waterlogging at booting stage and flow-ering stage was most serious. Comparing the three cultivars, X55 was most sensitive to waterlogging.     

Effects of Mg on C and N Metabolism of Soybean at Different Nitrogen Supplying Levels

A pot experiment was conducted to study the effects of magnesium on carbon and nitrogen metabolism of soybean at different nitrogen supplying levels. The results showed that the effects of magnesium at low nitrogen rate on N content, soluble protein, soluble sugar contents were not alike at different growth stage, although nodule dry weights raised, the yield and protein content of seeds decreased, however, the oil content was improved. The application of magnesium at medium and high nitrogen supplying levels promoted the uptake of N effectively, increased the soluble protein and soluble sugar contents, but the nodule dry weights of application magnesium at medium nitrogen supplying level decreased and the yield increased only a little despite the improved quality. Application of magnesium at high nitrogen supplying level raised nodule dry weights and soybean yield significantly, the quality of seeds was also improved.     

Single-seed sowing increased pod yield at a reduced seeding rate by improving root physiological state of Arachis hypogaea

Double-seed sowing(two seeds per hole) is the dominant pattern of peanut sowing in China, but within-hole plant competition usually limits their growth and yield formation. Besides, the traditional double-seed sowing method does not facilitate mechanization during sowing. The objective of this study was to determine if single-seed sowing at a proper seeding rate yielded better than traditional double-seed sowing pattern and the differences of physiological metabolism of roots. A field experiment was conducted in two consecutive years to compare pod yields of single-seed sowing at 180 000(S180), 225 000(S225), and 270 000 seeds ha~(–1)(S270) with that of double-seed sowing at 270 000 seeds ha~(–1)(D270) using a completely randomized block design with four replications. And the root bleeding sap rate, nutrient content, and the main hormone contents in root bleeding sap were also comparatively investigated. Although the pod yields of single-seed sowing at the three densities were higher than that of traditional double-seed sowing(D270), S225 yielded better than the other two single-seed sowing treatments(S180 and S270). The increased pod yield in single-seed sowing at 225 000 seeds ha~(–1) was mainly due to the higher pod dry weight per plant and harvest index. The improved pod dry weight and shoot growth had closely relationship with the enhanced root physiological traits such as the increased root bleeding sap rate, content of free amino acids, soluble sugars, K~+, Mg~(2+), Zn~(2+), and Ca~(2+) of the individual plant root. The improved activity of root reductive, nitrate reductase(NR) and ATPase and higher zeatin and zeatin riboside(Z+ZR) content of root bleeding sap were alsocrucial to the pod and shoot growth of peanut. Single-seed sowing at a moderate seeding rate(S225) is a potential practice to increase pod yield and to save seed cost.     

Physiological Mechanism of High and Stable Yield of No-tillage Cast-transplanted Rice

Four years‘ successive comparative experiments showed that no-tillage cast-transplanted rice (NTCTR), compared with conventional tillage cast-transplanted rice (CK), grew slower and produced less tillers at the early growing stage; but, it had shorter ineffective tillering time, less nutrition consumption,stronger individual growth and more uniform growth between individuals andthe colony. These characteristics contribute to the increase not only in the productive tiller percentage but also in the ear quality. Furthermore,the flag leaf of NTCTR had higher photosynthetic rate during the filling stage and no early senescence phenomenon at the late stage, which facilitated the accumulation and the transportation of carbohydrates and improved grain setting rate.     

Genotypic and Environmental Variations of Arabinoxylan Content and Endoxylanase Activity in Barley Grains

Arabinoxylan (AX) content in barley grains is an important quality determinant when barley is used as raw material of malt or beer production. The cultivar and environmental variations of total arabinoxylan (TAX), water extractable arabinoxylan (WEAX) and endoxylanase activity (EA) were investigated using eight barley cultivars growing at seven locations with diverse environmental conditions. The results showed that both barley cultivar and location significantly affected the TAX, WEAX and EA levels, but the variations of TAX content and EA were mainly attributed to cultivar, while the impact of location on WEAX content was greater than that of cultivar. Correlation analysis indicated that TAX was significantly correlated to WUAX.     

Comparison of Phosphorous Absorption, Quality and Yield Between High Oil Corn and Common Corn as Influenced by Phosphorous Application

A field trial was carried out to investigate phosphorous (P) absorption, grain quality and yield between high oil corn and common corn. The results indicated that high oil corn var.Tongyou 1 obtained lower highest P absorption rate (HAR) and later occurring date of HAR, in comparison with common corn var. Simi 25. The highest HAR and the earliest occurring date of HAR was obtained by the treatments of P45 and P75 in Tongyou 1 and Simi 25 separately; while the total amount of P accumulated by maize plant was achieved by P105 treatment in both varieties. P in grain relied mainly on root uptake at maturation that accounted for 85.7-96.8% and 79.3-84.3% for Tongyou 1 and Simi 25, respectively. Tongyou 1 contained more oil and protein contents, but less starch content with lower grain yield. P application at appropriate rate enhanced contents of protein and fatty acid, but the increment of starch content was neglectable.     

Effects of Low-temperature and Herbicide on Membrane Stability,Antioxidant Capacity, and Product of Metabolism in Barley Seedlings

In order to investigate the physiological injury of barley caused by the low temperature after herbicides, tillering barley seedlings planted in plastic cups were pretreated in illumination incubator at 15℃ and 12 h-light per day for 7 days, and then subjected to herbicide treatment, prometryn (with the concentrations of 0, 0.15%, 0.30%, and 0.45%) or isoproturon (with the concentrations of 0, 0.30%, 0.60%, and 0.90%), and the SOD activity, the CAT activity, the POD activity, the MDA content, proline content, soluble protein content, electrical conductivity, and the rate of O2-were determined and analyzed. The results showed that the low-temperature was the most important, and the treatment-time of low-temperature was another significant influencing factor on the physiological and biochemical indices of barley seedlings. However, all of the physiological and biochemical indices determined were not affected by the kinds of herbicides and herbicide concentrations, and the SOD was stable and should play the more prominent role on extracting of free radicals according to the stepwise regression and correlation. The herbicide concentrations should be increased in the future research for truly reflecting the effects of the herbicide concentration on the physiological and biochemical indices of barley seedlings.     

Responses of Ryegrass(Lolium perenne L.) Grown in Mudflats to Sewage Sludge Amendment

Sewage sludge amendment(SSA)is an alternative waste disposal technique and a potential way to increase fertility of mudflats for crop growth.The present study aimed to assess the suitability of SSA by assessing the nitrogen(N)and phosphorous(P)uptakes,heavy metal accumulation,growth,biomass,and yield response of ryegrass(Lolium perenne L.)at 0,30,75,150,and 300 t ha-1 SSA rates at various growth stages.The results showed that the highest biomass of ryegrass at seedling and vegetative stages were at 300 and 150 t ha-1 SSA rate,respectively.The increments of ryegrass yield at reproductive stage at 30,75,150,and 300 t ha-1 SSA rates were 98.0,122.6,88.1,and 61.2%,compared to unamended soil.N and P concentrations in ryegrass increased with increasing SSA rates at all stages except N and P in roots dropped significantly at 300 t ha-1 rate at vegetative stage.The metal concentration for Mn,Cu,Zn,Ni,Cd,Cr,and Pb in shoot of ryegrass at300 t ha-1 SSA rate increased by 0.63-,2.34-,15.02-,0.97-,10.00-,0.01-and 1.13-fold,respectively,compared to unamended soil.However,heavy metal concentrations in shoot of ryegrass were lower than the standard for forage products in China.The study suggested that sewage sludge amendment in mudfl at soils might be feasible.However,the impacts of sludge application on edible crop plants and soil environment need further investigations.     

Responses of Ryegrass （Lolium perenne L.） Grown in Mudflats to Sewage Sludge Amendment

Sewage sludge amendment （SSA） is an alternative waste disposal technique and a potential way to increase fertility of mudflats for crop growth. The present study aimed to assess the suitability of SSA by assessing the nitrogen （N） and phosphorous （P） uptakes, heavy metal accumulation, growth, biomass, and yield response of ryegrass （Lolium perenne L.） at 0, 30, 75, 150, and 300 t ha-1 SSA rates at various growth stages. The results showed that the highest biomass ofryegrass at seedling and vegetative stages were at 300 and 150 t ha-1 SSA rate, respectively. The increments of ryegrass yield at reproductive stage at 30, 75, 150, and 300 t ha1 SSA rates were 98.0, 122.6, 88.1, and 61.2%, compared to unamended soil. N and P concentrations in ryegrass increased with increasing SSA rates at all stages except N and P in roots dropped significantly at 300 t ha-1 rate at vegetative stage. The metal concentration for Mn, Cu, Zn, Ni, Cd, Cr, and Pb in shoot of ryegrass at 300 t ha-1 S SA rate increased by 0.63-, 2.34-, 15.02-, 0.97-, 10.00-, 0.01- and 1.13-fold, respectively, compared to unamended soil. However, heavy metal concentrations in shoot of ryegrass were lower than the standard for forage products in China. The study suggested that sewage sludge amendment in mudflat soils might be feasible. However, the impacts of sludge application on edible crop plants and soil environment need further investigations.     

Nutrient Status and Dynamics of Trifolium spp. at Different Growing Stages

The nutrient status and dynamics of three clover （Trifolium spp.） varieties at different growth stages were investigated with the crude protein content as an indicator of nutrient equilibrium. The crude protein, neutral detergent fiber （NDF）, phosphorus （P）, and calcium （Ca） content followed a decreasing trend at the initial growing stage and increased later. NDF and Ca content peaked in May, while crude protein and P content reached the highest in May and the lowest in July. The crude ash content followed an uncertain pattern as plants growing. The ash content of both wild-type red clover （T. pratensis L.） and ＇Sativum＇ decreased at the beginning and then increased. However, the ash content of ＇Revendef white clover （T. repens L.） decreased all through the experimental period. The general trend was observed for all three clover varieties as the ash content was the highest at vegetative growing stage （May）, and the acidic detergent fiber （ADF） content increased with time. The nutrient equilibrium value was ranked as ＇Revendei＇〉wild-type red clover〉＇Sativum＇.     

Effects of Ridge-Mulching with Plastic Sheets for Rainwater-Harvesting Cultivation on WUE and Yield of Winter Wheat

A field experiment was conducted in a manural loesial soil in middle of Shaanxi Province of China, a sub-humid area prone to drought, to study the effects of rainwater-harvesting cultivation on water use efficiency (WUE) and yield of winter wheat. Ridge-furrow tillage was used, the ridge being mulched by plastic sheets for rainwater harvesting while seeding in the furrows. Results showed that from sowing to reviving stage of winter wheat, water stored in 0-100cm layer was significantly decreased whereas that in 100-200cm layer did not change. Compared to the non-mulching, plastic mulch retained 6.5mm more water as an average of the two N rate treatments, having a certain effect on conservation of soil moisture. In contrast, at harvest, water was remarkably reduced in both the 0-100cm and the 100-200cm layers, and mulched plots consumed 34.8mm more water as an average of the two treatments: low N rate (75kg N ha^-1) with low plant density (2300000 plants ha^-1) and high N rate (225 kg N ha^-1)with high plant density (2800000 plants ha^-1) , in 0-200cm layer than those without mulching, the former being beneficial to plants in utilization of deep layer water. Mulching was significant in harvesting water and in increase of yield. Mulched with plastic sheets, biological and grain yields were 22.5 and 22.6% higher for the average of the high N rate than for the low N rate,and the high N rate with low plant density was 29.8 and 29.1% higher in both biological and grain yields than that of the low N rate with low plant density. With high N rate and high plant density, the mulched biological and grain yields were 39.5 and 28.9% higher than the corresponding treatments without mulching. Of the treatments, that with high N rate and low plant density was the highest in both biological and grain yields, and the water use efficiency reached 43.7kg mm^-1 ha^-1 for biological yield and 22 kg nn^-1 ha^-1 for grain yield, being the highest WUE reported in the world up to now.     

Short Response of Spring Wheat to Tillage,Residue Management and Split Nitrogen Application in a Rice-Wheat System

A ifeld experiment was conducted to study the impact of tillage, crop residue management and nitrogen （N） splitting on spring wheat （Triticum aestivum L.） yield over 2 yr （2010-2012） in a rice （Oryza sativa L.）-wheat system in northwestern Pakistan. The experiment was conducted as split plot arranged in randomized complete blocks design with three replications. Treatments comprised six tillage and residue managements：zero tillage straw retained （ZTsr）, zero tillage straw burnt （ZTsb）, reduced tillage straw incorporated （RTsi）, reduced tillage straw burnt （RTsb）, conventional tillage straw incorporated （CTsi）, and conventional tillage straw burnt （CTsb） as main plots and N （200 kg ha-1） was applied as split form viz., control （no nitrogen＆no splitting, N0S0）;2 splits of total N, half at sowing and half at the 1st irrigation （i.e., 20 d after sowing （DAS）） （NS1）;3 splits of total N, 1/3 at sowing, 1/3 at the 1st irrigation, and 1/3 at the 2nd irrigation （NS2）;4 splits of total N, 1/4 at sowing, 1/4 at the 1st irrigation, 1/4 at the 2nd irrigation （45 DAS）, and 1/4 at the 3rd irrigation （70 DAS） （NS3）;and 4 splits of total N, 1/4 at the 1st irrigation, 1/4 at the 2nd irrigation, 1/4 at the 3rd irrigation, and 1/4 at the 4th irrigation （95DAS） （NS4） as sub plots. The results showed that the most pikes m-2, grains/spike, 1 000-grain weight, grain yield, and N use efifciency （NUE） were obtained at zero tillage, straw retained and 4 splits application of total N （i.e., at sowing 20, 45 and 70 d after sowing）. The results indicated that ZTsr with application of 200 kg N ha-1 in 4 equal splits viz. at sowing 20, 45 and 70 d after sowing is an appropriate strategy that enhanced wheat yield （7 436-7 634 kg ha-1） and N efifciency （28.6-29.5 kg kg-1） in rice-wheat system.