| We evaluated the effect of ridge and furrow rainfall harvesting technique on alfalfa grassland yield, water use efficiency, profile soil water dynamics, soil nutrient dynamics and the decomposition feature of alfalfa root and litter, and the soil ecological stoichiometry feature by 2 years field experiment in the semi-arid Loess Plateau (Beishan of Yuzhong County, Gansu Province). We also assessed the influence of nutrient applying on fenced natural vegetation aboveground biomass, belowground biomass, root/shoot ratio, the soil ecological stoichiometry feature, and the effect of nutrient applying on vegetation establishment. To this end, four experiments had been conducted in Beishan of Yuzhong County. In the First experiment, five treatments were used:1) CK:Conventional cultivation in flat treatment without mulch; 2) M30: Plastic mulched ridge with the width of ridge and furrow as 30cm; 3) M60:Plastic mulched ridge with the width of ridge and furrow as 60cm; 4) B30:Bare ridge with width of ridge and furrow 30cm; 5) B60:Bare ridge with width of ridge and furrow 60cm. The second experiment: Alfalfa root and shoot litter decomposition embedded field test. There were also five treatments as to the first. The third experiment:the effect of ridge and furrow rainfall harvesting technique on the decomposition of five crops residue, roots and organic fertilizer:it had tow treatments:1) F:Flat treatment without mulch; 2) H:Plastic mulched ridge with the width of ridge and furrow as 60cm. There were four treatments in the last-the effect of nutrient applying on the soil ecological stoichiometry and vegetation establishment:1) CK:Contrast, no fertilizer; 2) N:Add nitrogen fertilizer; 3) P:Add phosphate fertilizer; 4) NP:Add nitrogen+phosphate fertilizer. The main results as below:1. The first Experiment:1) M60 has been proved to be the effective way of increasing alfalfa production, while B30 and B60 have a negative effect in 2008 and 2009. The order of production on different water harvesting regimes was M60>M30>CK>B60>B30, which was the same as the results of seven years ago. M60 had a higher WUE rather thanhigher water consumption, besides, M60 had a positive effect of water complement on soil 0-100cm layer.2) Alfalfa cultivation can enhance soil organic matter in the 0-20cm layer of soil. Even though it can reduce C/N, which means the acceleration of decomposition of SOC and decrease SOC content, in our experiment M60 play a better role on decreasing C/N.2. The second Experiment:1) Decomposition rate (K) of alfalfa root was higher than litter: KM60R(0.0029)> KM60L(0.0021), KM30R(0.0025)> KM30L(0.0012), KB60R(0.0025)> KB60L(0.0014), KB30R(0.0023)> KB30L(0.0014), KCKR(0.0022)> KCKL(0.0014). The decomposition rate of litter has a significantly positive correlation with its initial nitrogen content and C/P ratio, while it has a significantly negative correlation with its initial C/N ratio.2) In the field, roots and litters released more organic carbon (SOC was significantly lower than before decomposition) in the former 90ds, then slowly. The alfalfa litter in M60 has the highest organic carbon release, which was 81.0g/kg. The soil total nitrogen (exclude B30) and soil total phosphorus content increased in all root and litter decomposition treatments than before after 450ds. It showed nutrient enrichment in the soil.3) Alfalfa root and litter C/N ratio decreased significantly than initial value after decomposition. The order of C/N ratio decrease in different ridge and furrow rainfall harvesting technique was M30 (9.7)>M60 (9.48)>CK (9.27)>B60 (8.41)>B30 (7.24) for alfalfa root, while it was CK (9.59)>M30 (9.27)> B30 (7.91)> M30 (7.69)> B60 (5.69) for alfalfa litter.4) Decomposition rate is closely related to its chemical composition and affected by environmental factors. We found the decomposition rate of alfalfa root and litter had a significantly positive correlation with soil water content in the 0-20cm layer.5) SOC increased in different extent after 450ds decomposition of alfalfa root and litter in the field, which is in the 0-20cm layer soli of residue near 2-3cm. Furthermore, SOC from alfalfa root was more than it from litter. The soil C/N ratio has increased along the time goes. M60 has the highest C/N ratio (9.20) after alfalfa root decomposition while CK and M30 have the lowest C/N ratio (8.50) after alfalfa litter decomposition. Besides, soil C/N ratio after alfalfa root decomposition was higher than it after litter decomposition. The soil available phosphorus content differed in different treatments after 450ds decomposition, which was bare soil treatments> CK> film mulched treatments and M60 has the lowest soil available phosphorus content. The soil available phosphorus from alfalfa litter was 5.54mg/kg in B30, 5.53mg/kg in CK,5.29mg/kg in B60,4.43mg/kg in M30, and 3.66mg/kg in M60. After 450ds decomposition, C/P ratio in all treatments was higher in root than in litter and film mulched treatments> bare soil treatments and CK. M60 has the highest C/P ratio and CK has the lowest.3. The third Experiment:The decomposition rate of wheat, maize, pea, potato and alfalfa shoot, root and manure were accelerated under ridge and furrow with film mulched rainfall harvesting technique and it was positively correlation with 0-20 cm soil water content.4. The last Experiment:The productivity of fenced natural vegetation was enhanced by applying P fertilizer and N fertilizer, the productivity by applying P fertilizer was the highest. But applying P fertilizer can't enhance productivity. Adding N fertilizer would increase soil water consumption, and apply P, NP fertilizer can benefit the soil water. Our results showed, SOC and soil C/N ratio in the 0-20cm layer of soil were decreased by applying N fertilizer, but increased by applying P, NP fertilizer. Besides, by applying P fertilizer in restoration land could prevent C/N ratio decreasing. Thus, applying P fertilizer was an effective way for fenced vegetation to establish and restore.
|
PDF Full Text Request