**3. Results**

#### *3.1. Yield of Cereals in Pure Sowings and Mixtures*

The average yield of grain of spring cereals in the organic crop rotation was 18% lower than in the integrated one (Table 4). On average, spring cereal mixtures (SCMs) yielded 8.5% higher than pure sowings. For pure sowings, the lowest was the yield of oats, by 13% less than that of spring barley. Among SCMs, the highest yield was for oats and barley, by 22.6% more than for oats in pure sowing. Moreover, the average yield of a mixture of oats and triticale was 8.4% higher than the yield of oats in pure sowing. The yield of a mixture of triticale and barley was similar to that of a barley in pure sowing, but 11.4% higher than triticale in pure sowing (Table 4).


**Table 4.** Grain yield (t ha−1) of spring cereals grown in pure sowings or in mixtures in integrated or organic crop rotation, means for the years 2011–2019.

> 1 Means with various letters are significantly different, according to Tukey test (*p* ≤ 0.05).

The grain yield of individual components of SCMs was significantly differentiated (Table 5). On average, grain yields in the integrated crop rotations were 19% higher than in the organic ones. The lowest yield was for the oats in the mixture with triticale in the organic crop rotation. In turn, the barley mixed with oats in the integrated crop rotation yielded the highest (Table 5).



1 Means/values with various letters are significantly different, according to Tukey test (*p* ≤ 0.05).

#### *3.2. Leaf Area Index of Cereals in Pure Sowings and Mixtures*

The data presented in Table 6 show that the distribution of average values of leaf area index (LAI) for both crop rotations, as well as pure sowings and SCMs, was similar to those for the grain yield (Table 3). The mean value of LAI for the integrated crop rotations was significantly higher than for the organic ones. The values of LAI for SCMs were 9.7% higher than for pure sowings. The highest LAI was recorded for a mixture of oats and barley; it was higher than that of a pure sowing of oats and pure sowing of barley, by 28% and 8%, respectively.


**Table 6.** Leaf area index (m<sup>2</sup> m<sup>−</sup>2) of cereals in pure sowings or in mixtures in integrated or organic crop rotations, means for the years 2011–2019.

1 Means with various letters are significantly different, according to Tukey test (*p* ≤ 0.05).

A detailed analysis of LAI for the components of the mixtures revealed that oats in the SCMs had a significantly lower LAI; each time, the value of LAI of oats in the SCMs was below 1. The highest LAI was recorded for barley in the SCMs. What is more, the LAI of barley in the mixture with oats was 30% higher than that of oats (Table 7).

**Table 7.** Leaf area index (m<sup>2</sup> m<sup>−</sup>2) of the components of the spring cereal mixtures in integrated or organic crop rotations, means for the years 2011–2019.


1 Means with various letters are significantly different, according to Tukey test (*p* ≤ 0.05).

#### *3.3. Competition Indices for the Mixtures*

Expressing the cereal grain yields as a land equivalent ratio (LER), which shows the productivity of the SCMs, it was found that the LER values for all the SCMs were higher than 1 (Table 8). An SCM of oats with barley, followed by a mixture of oats with triticale and a mixture of barley with triticale, had the highest yielding potential, that is, the highest LER. Moreover, the system of crop rotation, integrated or organic, significantly differentiated the LER value, which was on average 4% higher in the organic system.

**Table 8.** Values of land equivalent ratio (LER) for the components of the spring cereal mixtures in integrated or organic crop rotations, means for the years 2011–2019.


1 Means/sums with various letters are significantly different, according to Tukey test (*p* ≤ 0.05).

On contrary, the competitive ratio (CR) for the integrated and organic crop rotations was similar (Table 9). For this indicator, both the competitor's species and the component species in the SCM were key. Thus, triticale had the highest CR in the SCMs. Barley was a competitor to oats but underwent competitive pressure when mixed with triticale. Oats undergo competitive pressure in all of the SCMs, with spring barley being the strongest competitor to it.

**Table 9.** Values of competitive ratio (CR) of the components of the spring cereal mixtures, means for the years 2011–2019.


1 Means with various letters are significantly different, according to Tukey test (*p* ≤ 0.05).

#### *3.4. Economic Indices for the Mixtures*

The results presented in Table 10 relate to research carried out in the mountainous area of southern Poland. The basic function of these areas is protection and retention of water resources. Table 10 contains economic measures for the cultivation of spring cereals and spring cereals mixtures. The average direct costs in the integrated system (EUR 481.9 ha−1) were 39.1% higher than in the organic system (EUR 293.5 ha−1). The highest share in the direct costs in the integrated system can be attributed to the application of mineral fertilizers, EUR 138.5 ha−<sup>1</sup> on average.

**Table 10.** Economic indicators of pure and mixed sowings of spring cereals in integrated or organic crop rotations (EUR ha−1); prices for the year 2019.


I—integrated; O—organic; SGM—standard gross margin. Conversion rate of 1 EUR = 4.2585 PLN in accordance with the National Polish Bank exchange rate on 31 December 2019.

The average value of direct surplus without subsidies was almost twofold higher in the organic system than in the integrated one. A greater disproportion between the examined systems occurred, when subsidies were added to the direct surplus (Table 10). The sum of subsidies for both cereals in pure sowing and mixtures is the same, and equal to EUR 177.9 ha−<sup>1</sup> and EUR 363.9 ha−<sup>1</sup> in the integrated and organic system, respectively.

The highest value of direct surplus without subsidies, among spring cereals, was obtained for spring barley (Table 10). This was because of the fact that pure sowings of spring barley yielded highest. The SCM of oats with barley also yielded high; however, the purchase price of the SCM grains was on average 10% lower than that of spring barley grains.
