The Effects of Some External Management Factors on the Nitrogen Composition of Cattle Manure on Smallholder Farms

Figure 4

Total organic N, neutral detergent insoluble N (NDIN), and acid detergent insoluble N (ADIN) dynamics in manure in the dry season experiment (DM basis). Error bars represent standard error of means. Continuous lines represent best-fit regression equations for organic N dynamics in manure during the dry season experiment. 𝑌 represents the amount of organic N, NDIN, or ADIN remaining in the manure (% of initial content, DM basis). The solid line (—) represents the Medium quality manure, no urine treatment. The dashed line (- - - -) represents the urine-amended Medium quality manure treatment. The dotted line (····) represents the Low quality manure, no urine treatment. The dot-dash line (-··-··) represents the urine-amended Low quality manure treatment. (a) Total organic N dynamics (% N, DM basis). Medium quality manure, no urine: 𝑌=100𝑒^{−0.00213𝑥}, 𝑅²=0.978. Medium quality manure, with urine: 𝑌=100𝑒^{−0.00768𝑥}, 𝑅²=0.916. Low quality manure, no urine: 𝑌=100𝑒^{−0.00087𝑥}, 𝑅²=0.971. Low quality manure, with urine: 𝑌=100𝑒^{−0.00327𝑥}, 𝑅²=0.982. The rate equations for NDIN dynamics between the four treatments did not differ at significance level α = 0.05. (b) NDIN dynamics (%NDIN, DM basis). Medium quality manure, no urine: 𝑌=100𝑒^{−0.00318𝑥}, 𝑅²=0.940. Medium quality manure, with urine: 𝑌=100𝑒^{−0.00994𝑥}, 𝑅²=0.823. Low quality manure, no urine: 𝑌=100𝑒^{−0.00202𝑥}, 𝑅²=0.945. Low quality manure, with urine: 𝑌=100𝑒^{−0.00529𝑥}, 𝑅²=0.961. The rate equations for organic N dynamics between the four treatments did not differ at significance level α = 0.05. (c) ADIN dynamics (%ADIN, DM basis). Medium quality manure, no urine: 𝑌=100𝑒^0.00528𝑥, 𝑅²=0.976. Medium quality manure, with urine: 𝑌=100𝑒^0.000918𝑥, 𝑅²=0.970. Low quality manure, no urine: 𝑌=100𝑒^0.000219𝑥, 𝑅²=0.951. Low quality manure, with urine: 𝑌=100𝑒^{−0.00288𝑥}, 𝑅²=0.964. Rate constants for ADIN dynamics in manure with no urine added differed between the manure sources (𝑃<0.0001). No difference was observed in the urine treatments (α = 0.05).

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(b)

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