Effects of nitrogen fertiliser application rate on nitrogen partitioning, nitrogen use efficiency and nutritive value of forage kale

Figures & data

Table 1 Background soil mineral nitrogen levels at the start of the experiment (initial) and at the final harvest (final), total dry matter yield, additional DM yield (difference between final DM and control crops), apparent NUE and stem and total N uptake.

	Mineral soil N (kg ha^−1)		Dry matter yield (t ha^−1)			N uptake (kg ha^−1)
Treatments (kg N ha^−1)	Initial	Final	Total	Additional^a	aNUE (kg DM kg^−1 N)	Total	Stem
0	84.9	32.8	6.7	–	–	85	49
50	110.7	26.6	12.3	5.6	111.6	144	91
100	91.6	33.0	15.1	8.4	83.6	153	102
200	68.8	27.2	19.1	12.5	61.8	226	155
300	103.5	38.4	21.9	15.2	50.8	281	186
400	75.5	46.1	21.4	14.7	36.7	343	244
500	84.6	47.5	25.5	18.7	37.5	425	282
LSD (5%)			3.2	3.5	38.0	66	53
P value			<0.001	<0.001	<0.01	<0.001	<0.001
d.f.			17	14	14	18	18

^aDifference between total DM and control yields for each treatment.

Figure 1 Accumulation of: A, Leaf (closed symbols) and stem (open symbols) DM; B, leaf area index; C, N uptake; D, specific leaf N for kale crops grown under different N rates. ● control, ▼ 50, ■ 100, ◆ 200, ▲ 300, ⬣400 and * 500 kg N ha¹, at Lincoln, in 2011–2012. Vertical bars represent the least significant differences (LSD _0.05; d.f. = 18). LAI_crit = critical leaf area index; SLN_crit = critical specific leaf nitrogen.

Figure 2 Correlation between: A, Total leaf DM and total DM yields (y = 0.15x + 0.27; R² = 0.84); B, leaf area index (LAI) and total leaf DM (y = 1.30x + 0.59; R² = 0.76); C, LAI and total leaf nitrogen uptake (y = 0.038x + 0.26; R² = 0.88); D, total leaf DM and total leaf nitrogen uptake (y = 0.026x + 0.93; R² = 0.89).

Table 2 Nutritive value of forage kale grown under seven nitrogen application rates at Lincoln, Canterbury in the 2011–2012 season and optimum range (NRC 2001; Nichol et al. 2003).

Treatment	Quality attribute*
kg N ha^−1	ADF	Ash	CP	Lipid	ME	NDF	SSS
0	28.7	6.8	7.7	1.9	12.4	41.9	33.2
50	27.5	7.5	10.2	1.8	12.7	41.9	31.3
100	30.6	6.8	8.6	1.6	11.9	43.5	29.8
200	30.8	6.5	7.8	1.6	11.8	46.0	30.0
300	28.1	7.3	9.4	2.1	12.3	41.1	32.0
400	27.4	7.3	10.5	1.7	12.7	42.0	30.7
500	30.3	7.2	9.3	1.8	11.9	42.3	28.8
LSD	2.6	0.7	3.4	1.1	0.7	4.7	6.0
P=	0.04	0.12	0.48	0.96	0.06	0.41	0.76
Mean	29.1	7.1	9.1	1.8	12.2	42.7	30.8
Optimum	>21	0.5	>12		10–11	>33	36–44

ADF, acid detergent fibre; CP, crude protein; ME, metabolisable energy; NDF, neutral detergent fibre, SSS, soluble sugars and starch.

*All units are % DM, except for ME (MJME kg⁻¹ DM).

NRC 2001. Nutrient requirement of dairy cattle. 7th edition. Washington, DC, National Research Council, National Academy Press. 408 p.

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Nichol W, Westwood C, Dumbleton AJ, Amyes J 2003. Brassica wintering for dairy cows: overcoming the challenges. In: Kilgour D ed. The smart side. Canterbury, Lincoln University, South Island Dairy Event (SIDE). Pp. 154–172.

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