Transferred Mulch System for Organic Reduced Tillage Vegetable Production

Annual Report 2023

SARE Project #FNE22-025

Objective 1—Measure dry matter production, percent nitrogen, and regrowth potential for multiple spring mulching materials and dates

Samples of mulch were taken from 3 different locations at each of 2 sampling dates (6 samples total,) and sent to Cumberland Valley Agricultural Services for analysis of dry weight and nitrogen content.  Half of each of the two plots (A15-17 and C1) which contained an overwintered small grain cover crop was harvested on the first sampling date, and the remaining portion of the plot was sampled on the second sampling date. This allowed us to assess how much additional growth occurred in that 3 weeks of growth.  The pasture plot (A13) was all cut on the first date, then allowed to regrow, and cut and sampled again on the second date.  The different management strategies reflect realistic options for managing mulch harvested from cover crops vs. pasture; the pasture is likely to yield less biomass on the first cut, but to allow for some regrowth to occur.  A13 was a well-established stand of mostly alfalfa that had rye seeded into it in fall 2022, and yielded more biomass than either of the small grain plots on the first cut, and then still yielded well on the second cut; the total biomass harvested on the two dates was much higher than the best yield of the small grain plots.

We did obtain measure carbon content of the mulch material in 2023, which allowed us to assess carbon:nitrogen ratios. The mulch material ranged from 20 to 30 C:N, which would indicate that it should decompose effectively and with little tie-up of nitrogen.

Table 1. Biomass and Characteristics of Mulch Harvested in 2023

Objective 2—Track nitrogen dynamics in mulched soil

Cucumbers were planted on three different dates in plots directly next to each other, with a field preparation and mulching regime as noted in Table 2 below.  A fourth plot was also sampled that was mulched with leaves collected from landscapers the previous fall. This plot was planted to brassica crops and onions.  Samples were taken from the plots at 8 dates during the season, and a Pre-Sidedress Nitrate Test was performed on the samples.  In addition to the 3 cucumber plots, we also tracked nitrate levels in a plot that was mulched with leaves and planted to brassica and onion crops. 

The PSNT results are summarized in Figure 1.  The release of nitrogen generally followed a similar pattern as the pattern observed in 2023, with an early flush of nitrogen availability followed by a tapering off over the course of the season.  The 2023 results showed a much lower overall nitrogen level, with only one sample out of 23 reaching 30 ppm, and most of the results below 20ppm (additional N fertilization is generally not recommended for cucumbers at PSNT results above 25-30 ppm).  It is likely that the yield of cucumbers was affected by lack of N, though no signs of N deficiency were observed in the field during the season. This lower N level could have been due to leaching due to a much wetter 2023 season.  It could also be that the baseline soil conditions were better in the 2022 fields.  Total organic matter and total soil N contents were both higher across the board for the 2022 fields than the 2023 fields.  The difficulty of side-dressing N during the season to address deficiencies is one drawback to the mulch system.  It may be that adjusting initial fertilization based on organic matter would be a good idea.  Feeding N through either drip-injection or through foliar feeding also may be a way to provide a nitrogen boost during the season.

Table 2. Cucumber Site information

Objective 3—Measure changes in soil health indicators over time

Soil Health Assessment and Comprehensive Assessment of Soil Health Test Results

Table 3: Soil Health In Field Assessment Results. Green cells indicate that the field met assessment criteria, red cells did not. 

The mulched plots all had the same soil health outcomes, other than slightly better soil structure in the leaf mulched plots which was likely more attributable to a different management history of this block than to the different mulch materials.  The history of B2 is that it had been managed with a heavy compost mulch and intensive no-till production since 2021.

Table 4. Selected Cornell Soil Health Test Results 

Transferred Mulch System for Organic Reduced Tillage Vegetable Production

Annual Report 2023

SARE Project #FNE22-025

Objective 1—Measure dry matter production, percent nitrogen, and regrowth potential for multiple spring mulching materials and dates

Samples of mulch were taken from 3 different locations at each of 2 sampling dates (6 samples total,) and sent to Cumberland Valley Agricultural Services for analysis of dry weight and nitrogen content.  Half of each of the two plots (A15-17 and C1) which contained an overwintered small grain cover crop was harvested on the first sampling date, and the remaining portion of the plot was sampled on the second sampling date. This allowed us to assess how much additional growth occurred in that 3 weeks of growth.  The pasture plot (A13) was all cut on the first date, then allowed to regrow, and cut and sampled again on the second date.  The different management strategies reflect realistic options for managing mulch harvested from cover crops vs. pasture; the pasture is likely to yield less biomass on the first cut, but to allow for some regrowth to occur.  A13 was a well-established stand of mostly alfalfa that had rye seeded into it in fall 2022, and yielded more biomass than either of the small grain plots on the first cut, and then still yielded well on the second cut; the total biomass harvested on the two dates was much higher than the best yield of the small grain plots.

We did obtain measure carbon content of the mulch material in 2023, which allowed us to assess carbon:nitrogen ratios. The mulch material ranged from 20 to 30 C:N, which would indicate that it should decompose effectively and with little tie-up of nitrogen.

Table 1. Biomass and Characteristics of Mulch Harvested in 2023

Objective 2—Track nitrogen dynamics in mulched soil

Cucumbers were planted on three different dates in plots directly next to each other, with a field preparation and mulching regime as noted in Table 2 below.  A fourth plot was also sampled that was mulched with leaves collected from landscapers the previous fall. This plot was planted to brassica crops and onions.  Samples were taken from the plots at 8 dates during the season, and a Pre-Sidedress Nitrate Test was performed on the samples.  In addition to the 3 cucumber plots, we also tracked nitrate levels in a plot that was mulched with leaves and planted to brassica and onion crops. 

The PSNT results are summarized in Figure 1.  The release of nitrogen generally followed a similar pattern as the pattern observed in 2023, with an early flush of nitrogen availability followed by a tapering off over the course of the season.  The 2023 results showed a much lower overall nitrogen level, with only one sample out of 23 reaching 30 ppm, and most of the results below 20 ppm (additional N fertilization is generally not recommended for cucumbers at PSNT results above 25-30 ppm).  It is likely that the yield of cucumbers was affected by lack of N, though no signs of N deficiency were observed in the field during the season. This lower N level could have been due to leaching due to a much wetter 2023 season.  It could also be that the baseline soil conditions were better in the 2022 fields.  Total organic matter and total soil N contents were both higher across the board for the 2022 fields than the 2023 fields.  The difficulty of side-dressing N during the season to address deficiencies is one drawback to the mulch system.  It may be that adjusting initial fertilization based on organic matter would be a good idea.  Feeding N through either drip-injection or through foliar feeding also may be a way to provide a nitrogen boost during the season.

Table 2. Cucumber Site information

Objective 3—Measure changes in soil health indicators over time

Soil Health Assessment and Comprehensive Assessment of Soil Health Test Results

Table 3: Soil Health In Field Assessment Results. Green cells indicate that the field met assessment criteria, red cells did not. 

The mulched plots all had the same soil health outcomes, other than slightly better soil structure in the leaf mulched plots which was likely more attributable to a different management history of this block than to the different mulch materials.  The history of B2 is that it has been managed with a heavy compost mulch and intensive no-till production since 2021.

Table 4. Selected Cornell Soil Health Test Results 

 Penetration Resistance

The location of the 2023 trial and the growing season of 2023 presented significant challenges for collecting penetrometer readings. The location of the 2023 mulch trial plots happened to be placed in a far more rocky and gravelly portion of the field than the 2022 trial, with the exception of a leaf-mulched plot (B2) that we also tracked in 2023, which was not very rocky. As a result, it was far more challenging to collect accurate data in B12 1-3. Standard practice was to stop at 12 points in a zig zag fashion across each trial strip, and attempt 5 times at each of the 12 points to collect both a surface and subsurface penetration resistance reading that was unimpeded by stones. After attempting 5 times and repeatedly hitting stones, we record “TR” for “too rocky” and move on to the next point. If we are able to collect a value for surface penetration but not for subsurface penetration resistance (6-18”) It is typically possible to detect larger stones interfering with the penetrometer and reset the instrument, but for very small stones it is not always possible for the operator to detect them. When there is a high prevalence of small stones, it can be very difficult to collect penetrometer readings that reflect soil hardness rather than gravelly areas of the soil. 

In many cases, our penetrometer records for 2023 include gaps in our data in which the operator was unable to collect data for any of the 12 points, because of the thickness of stones that blocked the penetrometer at all 48 attempts. This was far more common in the 6-18” depth range (subsurface). Additionally, heavy rains in July made it difficult to find a date to collect penetration resistance data in optimal field conditions (field moist soil). 

Ultimately, average plot penetration resistance fluctuated across the season in 2023 in plot B12 1-3, with no discernable trajectory. The variability of the readings is most likely attributable to the difficulty of collecting accurate readings with so many fine to medium stones. By contrast, B2, a far less stony field that was covered in leaf mulch that we tracked in 2023, appeared to gradually decrease and then increase in surface penetration resistance over the course of the growing season with a roughly opposite trend in subsurface resistance. This is an interesting and unexpected result.