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Termine

Effects of farmyard manure compost and biodynamic preparations

Long-term trial at IBDF Darmstadt (since 1980)

since 1992 Agroecology: Weeds in wheat and rye

Third period (research focus: Yield formation and long-term effects)

**Mean number of weed species in wheat and rye, by type and intensity of fertilization (Schnieders, 1996)**
Fertilization	Wheat	Rye
CM CMBD MIN	27.7 b 29.1 b 19.3 a	22.8 23.1 20.4
low medium high	24.2 a 24.7 a 27.2 b	21.6 22.2 22.5
Mean values within a half column with different letters are significantly different (p<0.05).

In the manure-fertilized wheat, the average number of weed species was much higher than with mineral fertilization.
The high fertilization intensity of wheat resulted in more species than the medium and low levels.

In rye, in contrast, generally less weed species were found, without any fertilization effects.

A total of 67 plant species were found, including 8 tree species and volunteer cereals or other preceding crops.

**Coverage (%) of crop and weeds in wheat (June 5-8, 1995) and rye (May 30 to June 2, 1995) by type and intensity of fertilization (Raupp et al., 1998)**
Fertilization	Wheat		Rye
	crop	weeds	crop	weeds
CM CMBD MIN	65.0 a 57.9 a 82.5 b	25.3 a 24.7 a 6.9 b	42.0 a 39.1 a 51.4 b	17.5 a 17.1 a 23.3 b
low medium high	53.8 a 68.3 b 83.3 c	15.7 20.4 20.8	38.5 a 47.4 b 46.6 b	16.9 18.9 22.1
Mean values of either type or level of fertilization of a crop with different letters are significantly different (p<0.05).

Weed coverage levels in wheat and rye responded differently to fertilization.
Mineral fertilization led to less weeds in wheat and more weeds in rye compared to the manure treatments. Weed coverage levels with manure fertilization were similar in both crops.

In both crops their coverage was higher with mineral fertilization than with manure fertilization.

Rising fertilization intensity increased crop density in wheat more than in rye, but no significant effect on weed density has been observed.

Relative incidence of light into the crops.
Owing to the higher crop density, the relative incidence of light was much lower with mineral than with manure fertilization (figures for wheat and rye), particularly with wheat into which only 10% of full light was measured at the soil surface instead of 20-30% as in the organically fertilized plots. A reduction in higher fertilized crops also occurred with both cereals.

A more dense crop also had a more dense weed population.
In most cases a positive correlation was found between the coverage levels of crops and weeds (see figures below; only with rye-CM and wheat-MIN did this relation not exist). In other words, if crop density was higher because of more intensive fertilization, weed growth was also stimulated.

**Dry matter, C and N content and N uptake of weeds in rye (in mid-July, EC 92) with manure (CM, CMBD) and mineral fertilization (MIN), medium intensity only (Raupp et al., 1998)**
Fertilization	DM kg ha^-1	% N	% C	C / N	N-uptake kg ha^-1
CM	653.1 b	1.39 a	41.1	29.6	9.07
CMBD	653.3 b	1.29 a	41.8	32.3	8.44
MIN	447.8 a	1.87 b	40.7	21.8	8.36
Mean values with different letters are significantly different (p<0.05).

The higher weed biomass in the manure fertilized crop did not cause a higher N uptake.
Corresponding to the higher coverage levels, weeds in the manure treatments produced a higher amount of dry matter than in minerally fertilized plots. However, N uptake by weeds was about the same in all treatments, since minerally fertilized weeds had higher N contents.


Grain yields of wheat and rye in 1995, fertilized with composted manure (CM, CMBD) and mineral fertilization (MIN) at 3 intensities (Raupp et al., 1998).

Differences between the treatments in yields of wheat and rye can not be explained by the respective weed populations.
Wheat gave about the same yield with organic and mineral fertilization, although there were considerably less weeds in MIN. Rye yielded higher if minerally fertilized, the weed population of which was also higher than in the organic treatments.

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