The decomposition of turfgrass clippings is fast at high air humidity and moderate temperature

Figures & data

Table I. Time of experiment, the duration of decomposition periods and sampling weeks.

Period	Duration of the experiment	Year	Total number of bags exposed	Sampling weeks
I (8 weeks)	15 May–10 July	2006	64	2, 4, 6, 8
II (8 weeks)	13 Sept–8 Nov	2006	80	1, 2, 4, 6, 8
III (10 weeks)	26 Oct–4 Jan	2006	48	2, 5, 10
IV (8 weeks)	16 May–10 Jul	2007	48	2, 4, 8

Table II. The dry matter (DM) content, nitrogen (N), carbon (C), cellulose and lignin initial concentration and C:N ratio in clippings at the beginning of Periods I–IV.

	N0^†	N80	N160	N400
	Period I
DM,%	28.3a^‡	26.4a	26.4a	26.3a
N, mg g^−1	24.3a	29.3b	30.5b	39.2c
C, mg g^−1	418.6a	418.7a	420.9a	417.6a
C:N	17.3c	14.3b	13.8b	10.6a
	Period II
DM,%	17.7b	16.9b	14.3a	14.4a
N, mg g^−1	42.3a	46.6a	53.9b	58.5c
	Period III
DM,%	28.7c	25.0b	21.8a	21.0a
N, mg g^−1	38.1a	42.1ab	48.2c	44.4bc
	Period IV
DM,%	28.6c	24.2b	23.1a	22.4a
N, mg g^−1	23.3a	38.5b	38.0b	45.2c
C, mg g^−1	425.5a	n.d.^§	n.d.	433.5a
C:N	18.2a	n.d.	n.d.	9.3b
Cellulose, mg g^−1	178.2a	n.d.	185.0b	175.1a
Lignin, mg g^−1	12.6a	n.d.	12.2a	12.2a
^†N0, N80, N160 and N400 means 0, 80, 160 and 400 kg N ha^−1.
^‡Different letters within each line indicate significant difference of the mean values at p <0.05.
^§n.d., not determined.

Table III. Weather parameters for test periods.

	Mean temperature, °C			Mean relative humidity, %			Precipitation, mm
Week	Average	Min	Max	Average	Min	Max	Average	Min	Max
Period I
1–2	10.4	7.8	13.9	74.1	52.6	94.5	30.2	0.0	13.4
3–8	17.1	8.2	26.6	76.2	58.0	97.0	57.0	0.0	23.8
1–8	15.3	7.8	26.6	75.7	52.6	97.0	87.2	0.0	23.8
Period II
1–2	12.9	7.2	15.9	90.3	81.0	98.0	6.0	0.0	6.0
3–8	6.4	−9.7	14.0	97.9	92.0	99.0	115.6	0.0	19.0
1–8	8.1	−9.7	15.9	95.9	81.0	99.0	121.6	0.0	19.0
Period III
1–2	0.05	−9.7	10.1	97.4	92.0	99.0	35.4	0.0	14.6
3–10	3.3	−4.8	10.0	98.4	90.0	99.0	79.0	0.0	11.2
1–10	2.6	−9.7	10.1	98.2	90.0	99.0	114.4	0.0	14.6
Period IV
1–2	16.6	9.6	24.4	80.1	66.0	98.0	53.6	0.0	23.0
3–8	16.3	12.6	20.3	83.7	70.0	98.0	76.2	0.0	14.0
1–8	16.3	0.0	23.0	82.5	66.0	98.0	129.8	0.0	23.0

Figure 1.  Turfgrass clippings weight loss, as percentage (%) of the initial dry matter (DM) weight, during decomposition in spring–summer 2006 (Period I), in autumn (Period II), autumn–winter (Period III) and in spring–summer 2007 (Period IV). Bars indicate confidence limits at p<0.05.

Figure 2.  Concentration of the lignin and cellulose in turfgrass clippings during decomposition (Period IV). Bars indicate confidence limits at p<0.05.

Figure 3.  Regressions of mean temperature and weight losses at different times of the decomposition process. The points at different temperatures indicate weight losses of the decaying material from different fertilization treatments. A: Week 1–8 y = −0.32x²+6.33x + 43.08 R²=0.46*** (polynom). B: Week 1–2 y = −0.32x²+6.30x + 9.15 R²=0.83* (polynom). C: Week 3–8 y = −1.58x + 53.09 R²=0.48* (linear). * Significant at p<0.05. *** Significant at p<0.001.

Table IV. Regressions of mean relative humidity and precipitation with weight losses at different times of the decomposition process.

Parameter (Climatic variables)	Linear regression	R^2
1–2 week
Mean relative humidity, %	Weight loss =− 1.15x + 126.36	0.71*
Precipitation, mm	Weight loss=−0.18x + 33.94	0.063ns^†
3–8 week
Mean relative humidity, %	Weight loss = 1.16x−67.82	0.95***
Precipitation, mm	Weight loss = 0.39x + 3.39	0.53***
1–8 week
Mean relative humidity, %	Weight loss = 0.21x + 45,63	0.074ns
Precipitation, mm	Weight loss = 0.084x + 54.33	0.034ns
*Significant at p<0.05.
***Significant at p<0.001.
^†ns, not significant.

Table V. Results of multiple regression analysis with backward stepwise of the test between weight losses of different weeks and mean temperature, mean relative humidity and precipitation.

Week	Intercept	Mean air temperature,°C	Mean air relative humidity,%	Precipitation, mm	Standard error of estimate	R^2	p
1–2	154.770 (6.442)^†	0.191 (0.088)	−1.352 (0.064)	−0.392 (0.040)	3.292	0.942	<0.0000
3–8	−41.294 (18.057)	1.225 (0.562)		0.687 (0.129)	7.527	0.703	<0.0000
1–8	−82.776 (15.695)	1.766 (0.234)	1.994 (0.176)	−0.380 (0.038)	4.342	0.736	<0.0000
^†Standard deviations are in parentheses.