Fertilization Effects On Alfalfa Production Characteristics And Soil Fertility

The objective of this study was to show the effects of applied N, P, and K on alfalfa, growing characterisrics, hay yields and selected soil properties in a complete split-plot experimental design at the establishment year. The main conclusions were as follows, 1. The Logistic and Gompertz model were done to describe alfalfa height dynamic growth. The results showed that the first cutting has much greater growth latent capacity and longer fast growth period than the second one, while the instantaneous and maximum growth rate of cut 1 were much higher than those of cut 2. In general, the K×P, K×N, K and N×P×K interaction were statistically significant on the height growth, followed by N×P and N treatments. The response to applied P was the lowest throughout the study. The relative higher instantaneous and maximum growth rate, prior entry into fast growth period guaranteed K fertilizer the document factor during alfalfa height development. 2. The mean value of individual selected alfalfa biological characteristics of cut 2 was higher than that of cut 1 except for the stem number and stem diameter. In terms of variation coefficient, applied N, P, and K fertilizer had greater influence on alfalfa shoots per plant, crown and stem diameter compared with other characteristics. K fertilizer significantly increased alfalfa height, stem number, stem and crown diameter, shoots per plant and crown depth with the addition of 60Kg P2O5 ha-1 in cut 1 and 90 Kg P2O5 ha-1 in cut 2. The effect of N×P interaction followed. P single applied situated the last. However, P fertilizer decreased alfalfa dry stem/leaf ratio and made the relative much leaf dry weight, which benefited the improvement of alfalfa quality. 3. P fertilizer adversely affected alfalfa total dry weight. And yield decreases ranged from 2.53-16.4% in cut 1 and 2.41-24.94% in cut 2. Except for P single applied, alfalfa yield increases all took place in other treatments. The application of 60Kg K2O ha-1 gave the highest yields of herbage in the first cutting, 28.52% increase in comparison with the check treatment as well as K60N30P120 treatment, 27.4% increase in the second cutting. Corresponding total dry matter production for K, K60N30P120, K60N30 and K60P90 was 22.74, 21.02, 20.74% increase compared with the CK, respectively. ANOVA analysis indicated that there existed significant K×N, N×P, P×K, and N×P×K interaction. K fertilizer extremely significantly increased alfalfa hay yields by 663.2Kgha-1 compared with no-K treatments. Alfalfa yields respond to applied 30Kg N ha-1 were higher than that of 60Kg N ha-1 applied, although the difference was not significant. The applied P negatively affected the dry matter production. There were no significant different between the check and P90 treatment. And both of them were higher than that of P120, P60, and P180. 4. Fertilization was not economically recommended in the establishment year, most of the treatments exhibited a net loss. But the application of 60Kg K2O ha-1 returned a relative highest profit of $ 637.36. The order of other treatments was KN30($382.94)>KP90($157.24)>KN60($139.16)>N60P90($130.04). So in alfalfa seedling year, the best return on fertilizer invested was with 60Kg K2O ha-1. 5. Multiple regression equation was development to describe the relationship between fertilizer and alfalfa yields. There was a negatively significant K×N interaction. Alfalfa yields were linearly increaced by the application of fertilizer K and N. 6. Soil PH was reduced gradually with the rates of applied P, 0.01-0.29 decreased when only P was applied. N×P, K×P, and N×P×K interaction delayed the decrease range. The OM% was increased when K fertilizer was applied, 0.02-0.08% higher than the initial soil level. Applied P and P×K interaction put off the decrease rate of NH4+-N, while CK, N30P120, N30P180 and N60P treatment had the relative larger decrease range, 8.91-13.53mgKg-1 lower than that before seeding. Total-P and NaHCO3--P rose with the rates of applied P, although a small amount of fertilizer P didn't contribute much to soil P sink. K fertilizer obviously increased soil NH4OAc-K, especially the K60N60P180 treatment, 33% higher than that before sowing. The NH4OAc-K of other treatments as N30P120, N30P180, N60, N60P60, N60P90 and N60P120 decreased at a range of 8.4-21.7mgKg-1. 7. The correlation analysis between soil tests, fertilizer rates and hay yields showed that only K fertilizer had significantly correlation with alfalfa yields, although the correlation coefficient was 0.5777. N fertilizer was negatively extremely significantly correlated with soil OM, total-N. A greatly significant correlation was showed positively between P fertilizer and soil total-P and NaHCO3-P, passively between P fertilizer and PH. When applied K, a extremely correlation was found between K fertilizer and soil OM, total-N, NH4+-N and NH4OAc-K.