Studies On Mechanism And Regulation Of Yield And Quality Formation Of Three Forage Crops

Three yrs experiment was conducted to study the comparison to nutrition value, nitrogen metabolism traits and high yield and high quality regulation of three forage crops from 2003 to 2005. Sudan grass hybrid, Euchlaena perennis and general corn were regarded as the researching objects, the analysis of physiology and biochemistry was applied in the lab. The three forage grasses were planted in the field to explore the differences of the yield and quality, the effects and the mechanism of population density, clipping and nitrogen application on the yield and quality. A potted planted experiment by 15N labeled was carried out to research the rules of nitrogen uptake, accumulation and partition in the three forage crops. The main findings were obtained as following: 1. Comparison to yield and quality of the three forage crops The fresh and dry matter yield of WC2 was high (fresh and dry matter yield were 249951.9 kg?hm-2 and 30745.5 kg?hm-2, respectively); that of ND108 was low (fresh and dry matter yield were 85152.7 kg?hm-2 and 20314.6 kg?hm-2, respectively) and E. perennis was medium (fresh and dry matter yield were 135821.2 kg?hm-2 and 17026.72 kg?hm-2, respectively). Five nutrition components yield of WC2 was higher than those of E. perennis and ND108 significantly, but the crude protein (CP), ether extract (EE) and nitrogen free extract (NFE) contents were lower than those of E. perennis and higher than ND108. The gross energy (GE) yield of WC2 was significantly higher than that of E. perennis and ND108, the leaves played an important role for GE yield in WC2 and E. perennis a, but the stalks was main in ND108. The CP and dry matter (DM) degradations in rumen of ND108 were the highest among the nutrition components, and were significant differences to WC2 and E. perennis. All the nutrition components degradations in rumen increased to a certain degree after silage. Sudangrass hybrid (Wancao2) is a valuable new-type forage grass, which is able to meet the need of stockbreeding developing in China. 2. Effects of density on yield and quality of WC2 With increasing of the density, the fresh and dry matter yield of WC2 increased. The five nutrition components contents were no differences at different densities while the CP, CF and NFE yield were increased with the increasing of density. CA and EE yield was high at low density, and all the nutrition components of leaves were higher than those of stalks. GS, PEP case, POD and CAT activities enhanced with the density increasing, but SOD activity and MDA content was high at medium density. The Chl.a, Chl.b and Chl.a+Chl.b contents increased under density augment conditions while the Chl.a/Chl.b was reverse. Considering the yield and quality, WC2 maybe cultured with 540,000plants/ha to harvest high yield and high quality. 3. Effects of mowing on yield and quality The yield and quality of WC2 were different to those of E. perennis at different densities. The fresh matter, CP and GE yield of WC2 clipped 3 times were high in the growing season, and those of E. perennis cut 2 times were high. With increasing of mowing times, the regrowth degradations in rumen reduced while the CF degradations contrary. The grasses degradations in rumen of WC2 and E. perennis were the highest of all the nutrition components at the first harvest stage. WC2 with 25cm stubble and E. perennis with 20cm stubble had high fresh and dry matter yield. The regrowth yield, CP content and CP yield were low at heavy cut intensity. So the clipping modes of WC2 with 25cm stubble and E. perennis with 20cm stubble mowed 3 times in the growing season would the ideal method to obtain the higher yield and the higher quality. 4. Effects of nitrogen application on yield and quality of two forage crops Nitrogen application increased the yield of WC2 and it applied, as basis fertilizers with the same rate were higher than nitrogen applied several times averagely. For E. perennis, nitrogen applied one time was better than several times averagely under the lower nitrogen rate conditions, but the situation under the higher nitrogen rate was reverse. The dry weight rate improved with increasing of nitrogen rate for both WC2 and E. perennis a. Comparing to the control, nitrogen application enhanced CP and EE content of WC2, especially the EE content correlated positively to nitrogen rate in this study. EE content of E. perennis was the higher when nitrogen applied one time. The control treatment had high CA content and nitrate content in the two forage crops. NFE content of WC2 increased withincreasing of nitrogen rate while that of E. perennis was reverse. The data on five nutrition components indicated that nitrogen supply was effective to improve the yield of 5 nutrition components of two crops. The CP, EE and CF yield of E. perennis were the higher when nitrogen applied one time with low rate. CP yield of WC2 increased with increasing of nitrogen rate and the CF, NFE yield were also high. Five nutrition components'yields were due to their content and dry matter yield under different nitrogen strategies. The treatments of nitrogen application had the higher content of every nutrition components than the control; so suitable nitrogen application modes would be taken to obtain the higher yield and quality products. 5. Nitrogen metabolism of two forage crops Nitrogen absorption of WC2 and E. perennis increased gradually, so the accumulation was low at early stage and high at later stage. For WC2, nitrogen uptake from fertilizers reduced but from soil increased gradually. E. Perennis planted 90days later absorbed from fertilizers reached the peak. Nitrogen uptake, utilization efficiency, production efficiency and nitrogen harvest index were high under nitrogen applied one time at low rate or several times averagely at high rate. Nitrogen accumulation of E. perennis was the higher with nitrogen supplied one time and its efficiency was higher than WC2. Nitrogen uptake intensity of WC2 was high when nitrogen applied as basis fertilizers with low rate, which was similar with applied several times averagely. Nitrogen absorption rate of E. perennis slightly increased after nitrogen supply and it was high with one time at low rate. Nitrogen application improved the activities of NR, GDH, DS and GOGAT in the two crops, and GDH, DS and GOGAT activities were positively correlated to nitrogen rate. As for GS activity was led to be low when nitrogen applied one time. The nitrogen metabolism traits of different crops maybe regard as the physiological bases for nitrogen rate and application stages. For WC2, the nitrogen rate did not exceed 600kg·hm-2 and applied with basis: dressing=1:2 in this study. But for E. perennis, nitrogen applied one time at 300kg·hm-2 level, and 600kg·hm-2 as same as WC2. 6. Impacts of nitrogen application on carbon metabolism traits Carbohydrates are the basis material for regrowth and their contents affect the progress of regrowth . The soluble sugar content enhanced with increasing of nitrogen rate, the results...