Effects of rates and methods of swine slurry application on crop N uptake and N distribution in the soil
Creators: name: Khan, Mafiz
Publisher: name: University of British Columbia
Year: 2010

description: A three year field study located approximately 60 km east of Vancouver, British Columbia has been conducted to study the effects of rates and methods of application of anaerobically stored swine slurry on the availability and distribution of N in the root zone. Swine slurry ranging from 3.30 to 4.98% dry matter was applied to a silt loam soil prior to seeding silage corn (Zea mays L.). Rates supplying 0, 173, 321 and 653 kg ha⁻¹ of total N in the first year; 0, 157, 336 and 538 kg ha⁻¹ in the second year and 0, 163, 309 and 430 kg ha⁻¹ the third year were injected to a depth of 30 cm or broadcast, using a Big A Waste Applicator for both methods. At the time of application nearly 64% of the slurry total N was in the NH₄₊ form. In addition to slurry treatment, starter N and amounts of P and K were applied, based on soil test values. Corn silage yield increased significantly in all the years with increasing rates of slurry N application up to 330 kg ha⁻¹. The 653 kg ha⁻¹ application rate reduced yield in the first year. Addition of 538 and 430 kg ha⁻¹ N in the second and the third years gave no further increase in yields over the 330 kg ha⁻¹ rate. Slurry injection gave an average (over all application rates) increase in silage yield of 18% the first year, 5% the second year and 9% the third year as compared to broadcast application followed by incorporation. One month after application maximum concentrations of mineral N were found in the 0-15 cm zone when the slurry was broadcast and in the 15-30 cm zone when it was injected. A greater quantity of mineral N was found in the root zone when the slurry was injected than broadcast, indicating greater conservation of slurry NH₄₊- N by the injection method. Maximum recovery of slurry N was associated with the 80 t ha⁻¹ application and was obtained two months after application. The highest net mineralization of slurry organic N occurred with 80 t ha⁻¹ and the proportion mineralized was likely determined by the climatic conditions (especially temperature and moisture). Between 6-28% of the applied N was lost during the growing season when 80 t ha⁻¹ of slurry was injected compared to 30-50% when the same rate was broadcast. Overwinter N loss was greater for the injection than the broadcast method because residual soil N values were higher for the later method. Volatilization and immobilization were thought to be the major mechanisms of N losses over the growing season. Overwinter N losses resulted mainly from leaching of NO₃₋ and probably denitrification as well, as there was no indication of any significant fraction of slurry N entering into the soil organic pool. The amount of fall precipitation and the form of N at the end of the growing season greatly influenced the quantity of overwinter N loss. Greater amounts of N were carried over when the slurry was injected as opposed to broadcast, and the amounts carried over increased with the increase in N application rate. However, in no case, did the maximum amount carried over exceed 16% of the applied N. The injection method of application was found to be more favourable for the use of slurry in crop production. Slurry N application should be adjusted based on target yield, soil N supply and the method of application being used. Factors such as reduced soil compaction immediately below the plough layer also could have increased crop yields as a result of the injection method.