| Dual-purpose is a production practice which uses vegetative grain crops for forage production initially (grazing or cutting), with subsequent harvesting of grain after a period of regrowth. This practice is widely used worldwide in countries such as America, Australia and Argentina. In order to explore the feasibility of the dual-purpose use of wheat (Triticum aestivum) in China, a series of investigations examining the dual-purpose potential of wheat were conducted during the years from2008to2013. Accumulated temperature requirement, dry matter and water soluble carbohydrate accumulation, and the nitrogen compensation were defined, in addition to a comprehensive economic income analysis. The main results of this study are listed below.1. Under irrigation conditions of Queensland in Australia, the forage and grain productivity of short-season spring wheat cultivar’Crusader’was lower compared with the spring wheat cultivar’Gregory’under same cutting time treatment. Under the same cutting time treatment at tillering stage, the forage yield of the’Crusader’cultivar was0.7t/ha less than that of ’Gregory’. The regrowth of’Crusader’was slower during the first10days, but greatly increased after this period, with dry matter accumulation, leaf area index (LAI), Photosynthetically active radiation interception (IPAR) and water soluble carbohydrate content (WSC) all being much higher than that of’Gregory’. Under the cutting treatment at tillering stage (5tillers), the grain yield reduction of’Crusader’and’Gregory’ was5%and10%compared with each uncut control. The regrowth ability of the short-season cultivar is great, and its grain reduction is much less than that of the long-season cultivar, making the short-season spring wheat cultivar much more appropriate for dual-purpose use.2. Under the rain-fed condition at the Longdong Loess Plateau during the years between2008and2010, the forage yield of winter wheat was approximately0.82-1.25t/ha when cutting was imposed at tillering stage, and its crude protein content (CP) was approximately20%-25%. The yield was significantly increased if cutting was imposed later than stem elongation stage, but forage quality was significantly reduced, with the CP content being only10%at flowering. The flowering and maturity date was delayed by0-4days, and the accumulated temperature requirement of each regrowth period was comparable to the uncut control (P>0.05), The flowering and maturity date was delayed by3-33days, and the accumulated temperature requirement was significantly increased by>137℃. Furthermore, the accumulated temperature requirement of period before stem elongation stage, and period between the booting stage and the inflorescence stage was greatly increased by>71℃and>80℃, respectively, however that of the period between flowering and maturity was significantly reduced by>148℃(P<0.05). There was no significant difference in grain yield and yield components between the tillering stage (5-6tillers) cutting treatments and the uncut control, and grain yield of the cutting treatments at tillering stage (9tillers) was greatly reduced by32%(P<0.05). Conversely, grain yield of the cutting treatment later than the stem elongation stage was significantly reduced by>62%(P<0.05), and the stubble yield, harvest index and yield components were also significantly lower than the uncut control (P<0.05). Most importantly, the forage yield and quality was relatively high and yield reduction was small when cutting was imposed at tillering, which is the appropriate stage for dual-purpose use. The stable accumulated temperature requirement between flowering and maturity is the inner mechanism of stable grain production, and accordingly the reduction of the grain yield and yield components was less in the season with fine rainfall condition.3. From2009to2011, the forage production of winter wheat was1.01t/ha when cutting was imposed at ground level at the Longdong Loess Plateau, and the yield was reduced by46%and81%when the cutting height was increased to3cm and6cm. Under the cutting treatment with residue height of0cm, the grain yield was reduced by16%(P>0.05) in the wet season, and dry matter accumulation, LAI, light interception at booting and flowering were greatly reduced (P<0.05), WSC was slightly reduced, and the grain yield was greatly reduced by34%in the dry season (P<0.05). Under the cutting treatment with residue height of3cm, the dry matter accumulation during the milk stage and maturity was increased, and the grain yield was significantly increased by24%, with the spike number per m2significantly increased by37%in the wet season(P<0.05). All the indexes were lower than that of the uncut control in the dry season, and the grain yield was reduced by31%(P>0.05). Under the cutting treatment with residue height of6cm, dry matter accumulation was less than the uncut control (P>0.05), but LAI, light interception and WSC at booting and flowering were higher (P>0.05), with the grain yield and the yield components comparable to the uncut control even in the dry season (P>0.05). The biomass of regrowth at booting and flowering was positively correlated to the grain yield and the number of grains per spike (P<0.001). The grain yield could increase by0.5t/ha if the biomass at booting and flowering was increased by1000kg/ha, and it could increase by0.3t/ha and1.3t/ha if the WSC at booting and flowering was increased by1000kg/ha.4. Top-dressing treatments of0,60and120kg N/ha were applied at the Longdong Loess Plateau. The more nitrogen was added, the further the date of flowering and maturity were delayed, and the greater the accumulated temperature requirement of the whole growing season period. Grain and stubble yield, grain CP, yield components and plant nitrogen uptake were gradually increased. Under the top-dressing level of0and60kg N/ha, all these indexes are comparable with the uncut control, however, the grain yield was significantly reduced by18%(P<0.05), whereas the stubble yield was significantly increased by17%(P<0.05) and the harvest index was reduced by20%(P>0.05) under the top-dressing level of120kg N/ha, indicating that the compensation was obvious at the vegetative parts. The spike and the grain number per m2was increased by35%and11%, respectively (P>0.05), showing that grain yield could increased by improving the spike and the grain number per m2.5. After lamb grazing at winter for16days, the dry matter accumulation, the grain weight per m2and kernel weight during the grain filling of the grazed wheat was not significant different with that of the ungrazed wheat control (P>0.05), however the total dry matter and the WSC accumulation of each internode, and its transfer and contribution to the grain yield was reduced compared with the ungrazed control (P>0.05). The transfer and contribution of the dry matter to the grain yield of the peduncle was significantly reduced by24%(P<0.05) and the transfer and contribution of the WSC was significantly reduced by29%(P<0.05), which resulted in the significant reduction of transfer and contribution of the stem. No significant difference was found between grazed wheat and the ungrazed control in grain and the stubble yield, harvest indexes and the yield components (P>0.05). Above all, although the transfer and contribution of the dry matter and WSC to the grain yield of the stem were significantly reduced, the grain yield was not influenced, indicating that the increase of the photosynthesis is the inner mechanism governing the stability of the grain yield.6. The rate of the body weight gain during grazing of the lamb grazing wheat was166g/d/sheep, while that of control was88g/d/sheep, thus extra body weight gain after grazing of winter wheat is60kg/ha after grazing for16days. The grain yield of the grazed winter wheat was0.05t/ha less than that of the ungrazed control, and the total income of the dual-purposed winter wheat could increase by1400RMB/ha compared with the grain-only wheat according to the present price of grain and mutton. According to the economic analysis under different cutting managements, the proper dual-purpose management of winter wheat is cutting or grazing at tillering stage (5-6tillers) with a residue height of3cm, and top-dressed with urea at60kg N/ha.In this study, wheat was used as new material for the forage resource exploration, and the accumulated temperature mechanism, the dry matter and the water soluble carbohydrate basis and the compensation mechanism of the nitrogen were explored, and the best dual-purpose management of the wheat and its economic advantage was tested. These results have significant implications for the promotion of dual-purpose use in a large area in China, and it will benefit the development of the livestock industry and the production and income increase of the farmers. |
PDF Full Text Request