*3.4. Influence of Cover Crop Species and Barley Seeding Rate on Barley Yield and Malting Quality Characteristics*

There were no significant treatment effects on barley grain yield but there were two non-significant trends of note (Table 5). First, barley in SH and SH + CC treatments produced slightly more grain (3.74 and 3.67 t ha<sup>−</sup>1, respectively) than either CC (3.39 t ha−1) or NC (3.32 t ha<sup>−</sup>1). Given that the cover crop treatment groups had very different organic matter and nitrogen contributions the previous fall, the small difference in yield could be related to the larger differences in soil condition at barley planting. Second, there was a non-significant yield improvement as seeding rate increased, possibly related to differences in stand quality due to differences in initial barley seedling population and winter survival. However, as noted above, the differences in yield were small and showed that all of the experimental treatments examined in this study can be similarly productive in malting barley cropping systems.

**Table 5.** Mean grain yield and quality metrics for winter malting barley following different cover crops and barley seeding rates in South Deerfield MA in 2014–2015 and 2015–2016.


Note. \*, *p* ≤ 0.05; ns, non-significant according to non-parametric permutation tests. Although cover crop type had a significant effect on falling number, pairwise comparisons made using Bonferroni adjusted *t*-tests did not show significant differences between any cover crop types (*p* ≤ 0.05). Cover crop type is evaluated as a discrete effect and barley seeding rate as a continuous effect.

> As was the case with grain yield, there were no significant differences in malting barley grain quality among cover crops or barley seeding rates (Table 5). Across the experiment, mean test weight was 58.2 kg hl<sup>−</sup>1, mean 1000 kernel weight was 46.2 g, mean germinative energy was 82 percent, mean protein content was 111.2 g kg−1, mean falling number was 224 s, and mean DON content was 0.16 mg kg−1. Overall, while the barley met some malting quality standards, it fell below others. Protein and DON content were in good ranges for brewing purposes (below 125 g kg−<sup>1</sup> and 0.5 mg kg<sup>−</sup>1, respectively). Test weight and falling number were a little lower than standard malting quality for these two indices (61.8 kg hl−<sup>1</sup> and 250 s) while germinative energy was much lower than required for

malting (95 percent). There is no specific standard for 1000 kernel weight. Relatively low germinative energy may have been the result of high drying temperatures following grain barley harvest.

These results indicate that high nitrogen contributions from leguminous cover crops are unlikely to result in protein levels exceeding malting standards.

#### **4. Discussion**

Most malting barley production in North America occurs in the dry Great Plains and West Coast regions with relatively little in the humid Northeast and Midwest [1]. As a result, most malting barley research has focused on different cropping systems than those discussed in this experiment. Many experiments have been performed in much drier conditions [16–20,22,24,39] or with spring planted cultivars [3,16,17,22,24,39]. Furthermore, many studies have found substantial differences in malting quality even in winter malting barley cultivars [10,11,14,18]. Caution should be used when generalizing experimental results given the diversity of growing conditions across North America and the relative novelty of winter malting barley cultivation in the Northeast.

This experiment indicated that even though malting barley is quite sensitive to nitrogen level in grains [13,14,18], leguminous crops may be grown before winter malting barley without damaging the yield or malting quality of the barley crop (Table 5). This result differs somewhat from research on malting barley production following legume cover crops further north in New England. Darby et al. and Surjawan et al. [3,23] reported that sunn hemp cover crop before winter barley reduced the next summer's yield in Vermont [23] and that a pea/oat/vetch cover crop slightly reduced malting quality in spring barley in Maine [3]. That said, malting barley is much more sensitive to nitrogen in the spring than in the fall [13] and Darby et al. [23] did not find effects of either sunn hemp or crimson clover on malting quality.

In the American West, past studies have explored whether growing spring malting barley after legume cash crops could impact the grain yield and malting quality [16,17,39]. Sainju [17] found that pea residue retained soil nitrate better than bare fallow, while Sainju et al. [39] and Turkington et al. [16] found that planting spring barley after peas did not cause negative quality characteristics such as high protein content, which have been commonly seen from excess nitrogen fertilizer [13,14,18]. However, these experiments were done with a spring barley following peas seed harvest, and the residues would not have contained nearly as much nitrogen as a legume cover crop incorporated into the soil, as was performed by Surjawan et al. [3].

The sunn hemp growth and nitrogen content (Table 2, Figures 1–3) in this experiment were similar to those seen after a similar amount of time (45 days) by Clark [25] in New York, although the overall sunn hemp production was lower than that seen by Clark after 60 days or by Mansoer et al. in the American Southeast [27]. Crimson clover (CC) and the summer fallow (NC) produced much lower biomass and nitrogen yield (Table 2, Figure 1; Figure 3) but did not lead to lower barley yields (Table 5). Together these results suggest that the barley was neither in need of nor hurt by the extra nitrogen supplied by the SH and SH + CC treatments. Given that malting barley can have disease issues when grown directly after a grass crop [1], it is agronomically important that winter malting barley be grown after a high nitrogen producer like sunn hemp without negative effects. Additionally, this research supports the idea recommended by Shrestha and Lindsey [1] that winter malting barley could be grown after soybeans (*Glycine max* (L.) Merr.). The growing season in Massachusetts may be too short for this to be a feasible cropping system. However, these results show that farmers further south should not be especially concerned that nitrogen from a previous soybean (or other legume) crop would negatively affect grain quality of winter malting barley. Additionally, longer growing seasons under climate change conditions and the development of shorter season soybeans could make this sort of crop system more attractive in the future in Massachusetts and other New England states.

While the differences seen in this trial based on barley seeding rate were minimal, previous studies have found that an increased seeding rate led to better overall malting quality and lower protein content in particular [20,22,24] in spring planted barley in western North America. The results from this experiment do not substantively contradict these earlier findings. While farmers are unlikely to see large yield gains from higher seeding rates, there may indeed be a reduction in variability from a relatively small investment in seed. Indeed, this research agrees with Darby et al. [23], who also found that similar increases in seeding rate can promote winter survival, although not always affecting final yield or malting quality overall.

The overall malting quality of barley measured in this study was similar to that seen in other winter malting barley in the Northeast. As in other studies, the barley grain did not meet all malting quality standards [11,13,23]. The best practices for malting barley production in the Northeast are still under development and producers should not expect to get malting quality grain every year [2,14]. Given that malting barley in the Northeast can be quite variable and is much more affected by cultivar selection [3,10,11,14], spring fertilizer application [13], and harvest management [2,12], the results of the current experiment indicated that regional farmers can plan their cropping system without worrying that a previous leguminous crop may cause quality issues in following winter malting barley.

#### **5. Conclusions**

It remains challenging to achieve superior malting barley in the Northeastern United States. This could lead farmers to form the impression that there is little flexibility if they want to meet the required quality standards. However, while excess nitrogen has been shown to lead to poor malting quality, growing high-nitrogen-producing legumes before planting winter malting barley is unlikely to reduce the quality of the succeeding barley. Specifically, this study demonstrates that following a legume cover crop with winter malting barley does not reduce grain yield or malting quality in terms of protein content, test weight, 1000 kernel weight, germinative energy, falling number, or DON content. These results show that winter malting barley can be integrated into crop rotations with leguminous plants without negative impacts on barley growth, yield, and grain quality.

**Author Contributions:** Conceptualization, M.H. and H.D.; supervision, M.H.; formal analysis, A.S. (Arthur Siller) and A.S. (Alexandra Smychkovich); writing—original draft preparation, A.S. (Arthur Siller); writing—review and editing, A.S. (Arthur Siller), M.H., H.D. and A.S. (Alexandra Smychkovich). All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was partially funded by Northeast Sustainable Agriculture Research and Education, project number GNE 13-066.

**Data Availability Statement:** The data presented in this study are openly available at UMass Scholarworks.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
