Dr. Charlie White is a faculty member at Penn State University, specializing in soil nutrient behavior and management.

He has taught various courses, including Soil Nutrient Behavior and Management, Internship, Independent Studies, Thesis Research, and Supervised Experience in College Teaching.

His research focuses on sustainable agricultural systems, biogeochemical cycles, and nutrient management to promote productive and efficient nutrient use in cropping systems.

In this presentation, Charlie will share some of the key insights into managing cover crops for nutrient management and soil health that he has learned through twenty years of research, much of it conducted in partnership with farmers in the temperate, humid climate of the Mid-Atlantic USA.

These lessons include the importance of measuring and managing cover crop and soil organic matter carbon, nitrogen, and C:N ratios to balance nitrogen retention and supply; that a little bit of grass in a cover crop mixture goes a long way to reducing N leaching; and that a cover crop mixture with balanced species proportions will be the most multifunctional, but achieving evenness in the biomass is easier said than done.

Finally, Charlie will return to his roots in reflecting on the importance of mycorrhizal fungi to the phosphorus nutrition of crops, and why P stratification in no-till system may not be as much of a problem as we think because of these symbiotic organisms.

Register now – Earlybird tickets still available

Session Synopsis

Growing multiple vegetable crops across a farming operation the size of Harvest Moon requires constant decision-making, careful timing and a deep understanding of what crops need at every stage of growth. In this session, Josh will walk through how Harvest Moon manages nutrient applications across more than a dozen crops using a combination of field experience, soil and sap testing, and modern data tools.

He will explain how the team schedules and calculates nutrient inputs throughout the season, how they identify inefficiencies in the system, and how these insights feed into broader Integrated Pest Management strategies. By continually measuring and refining what happens in the field, Harvest Moon is able to reduce risk, improve crop health and optimise yield.

The session offers practical, real-world insights for growers looking to sharpen their nutrient strategies, improve efficiency and get more value from the data already available in their farming systems.

Register now – Earlybird tickets still available

LandWISE Conference 2026

Havelock North Function Centre
27 – 28 May 2026

Our “Soil Health for Profit” theme in 2026 is, in some ways, a return to the past. LandWISE arose out of work to combat soil erosion through use of minimum tillage and we’re returning to strip-till in 2026. A lot has been learned in the intervening years! Along with that, we’ll look at what can be done to measure and manage crop nutrition and soil health to ensure sustainability and long-term profitability.  

We have international speakers from Pennsylvania and Tasmania complementing national and local growers and experts. They will share how they set out to build profitable enterprises with a focus on soil health and an eye to wider sustainability ambitions. We’ve asked them to offer ideas of things to take home and apply or try – to feed the appetites of keen delegates.

We have talks from people applying regenerative principles in cropping, pastures and orcharding, talks on strip-till and crop-stacking, soil amendments and cover cropping, and managing and minimising the cost of nutrients. As always, expect representation of agritech covering a wide range of technologies.

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Register at Humanatix

All three treatments were then disced twice. Since the ground was so hard and dry, the first pass with the discs was quite blocky, but after the second pass, there were plenty of fines for a seedbed.

The Conventional and Hybrid treatments were both planted with Moata ryegrass (25 kg/ha). The Regenerative treatment was planted with triticale (80 kg/ha) and vetch (50 kg/ha). Butternut residue made drilling tricky as long “ropes” of dried vine blocked equipment. The hard, dry, rubbly surface in areas such as wheel tracks left seed above the ideal soil mix. Normally we would aerate as the last autumn operation, leaving the soil fractured over winter and spring. We think the butternut residue will make that extremely difficult, so have postponed it. If the soil is still dry enough once residues have rotted, we can aerate in a couple of months.

Thank you to Mike Kettle Contracting for doing our groundwork and planting our cover crops.

Because the soil is so dry, and with no rain on the Hawke’s Bay horizon, we are applying 12 mm of irrigation to ensure good establishment. Once complete, we plan to apply bait as our slug populations are extremely high and past experience showed they have major effects on cover crops, especially the vetch we have planted.

A big thank you to all the Operation Advisory Group members who have attended our weekly field walks and helped make decisions for our cover crops.

Carbon Positive is a partnership between LandWISE, the HB Future Farming Trust, McCain Foods, Heinz-Wattie’s and Process Vegetables NZ.

Our butternut hand harvest of replicated plots was completed on the 9^th and 10^th of March. Four subplots of 6m² were sampled from each plot. All butternuts within the sample area were cut from the plant, counted, and weighed. A butternut subsample was collected for Brix, dry matter, nitrogen, and carbon analysis. The plant residue was also weighed, and a subsample was collected for dry matter, nitrogen, and carbon analysis. Notably, although there are slight differences in the various metrics we assessed, none are significant at a 5% confidence level.

Butternut fruit yield

Yields were very high. We planted assuming 25 – 30 T/ha of butternuts but grew almost double that. The conventional treatment had an average yield of 52.74 T/ha, the Hybrid treatment had 52.00 T/ha, and the Regenerative treatment had 49.44 T/ha.

Butternut residue

The Conventional treatment had an average residue biomass of 20.57 T/ha, the Hybrid treatment had 20.25 T/ha, and the Regenerative treatment had 17.56 T/ha with differences again not significant.

Dry Matter

A subsample of butternut residue was dried to calculate the dry matter percentage. All three treatments had an average dry matter of 16%.

The Conventional treatment had an average dry matter of 8.44 T/ha, the Hybrid treatment 8.37 T/ha, and the Regenerative treatment 7.77 T/ha. While showing slight differences, these are again not significant differences between treatments (P>0.05).

Nitrogen percentage

The nitrogen percentage in the butternut plant residue was determined by Hill Laboratories. The Conventional treatment butternut residue had an average nitrogen percentage of 1.95%, the Hybrid treatment had 1.78%, and the Regenerative treatment had 1.70%.

To calculate the amount of nitrogen in the butternut residue, the dry matter (T/ha) was multiplied by the nitrogen percentage and converted to kg/ha. The Conventional treatment had 163.92 kg N/ha, the Hybrid treatment had 148.63 kg N/ha, and the Regenerative treatment had 131.97 kg N/ha.

Carbon percentage

The percentage of carbon in the butternut residue was determined by Hill Laboratories. The Conventional treatment had an average carbon percentage of 35.25%, the Hybrid treatment had 34.20%, and the Regenerative treatment had 35.50%.

The butternut residue dry matter (T/ha) was multiplied by the carbon percentage to get tonnes of carbon per hectare. The Conventional treatment had 2.95 T C/ha, the Hybrid treatment 2.86 T C/ha, and the Regenerative treatment 2.76 T C/ha.

Brix

To measure Brix levels, a subsample was taken from two butternuts from each sample area. The subsample was grated and squished in a garlic crusher, and the juice was tested with a Refractometer.

The Conventional treatment had an average Brix level of 7.1%, the Hybrid treatment 7.9%, and the Regenerative treatment 7.0%.

If Wattie’s had harvested the butternuts, Brix levels would have been assessed prior to harvest. Heniz-Wattie’s minimum brix level before harvest is 7%, ideally, they would be harvested between 9–10% brix. As the butternuts were harvested by a local grower approximately one month earlier than Heinz-Wattie’s standard harvest timing, the Brix levels were on the lower side.

Thanks, Phillip Schofield, Phillipa Page, Dan Bloomer, and Olivia Webster, for helping with the hand harvest.

A big thank you to all the Operation Advisory Group members who attended our weekly field walks throughout the season, providing us with their expertise and helping make decisions.

Carbon Positive is a partnership between LandWISE, the HB Future Farming Trust, McCain Foods, Heinz-Wattie’s and Process Vegetables NZ. Many thanks to our funders; MPI, Process Vegetables NZ, McCain Foods, Heinz-Watties and Hill-Labs.

Our hand harvest samples were taken from 3 m × 2 m areas within each of the four subplots of each plot; 16 per treatment, 48 in all. All butternuts within the sample area were cut from the plant, counted, and weighed. A subsample was collected for Brix, dry matter, nitrogen, and carbon analysis. The plant residue was also weighed, and a subsample was collected for dry matter, nitrogen, and carbon analysis.

On the 10th of March, the butternuts were cut for fresh market and placed into windrows ready to be collected into bins.

The main differences between treatments were cultivation method, biological and foliar applications, and fertiliser inputs. The Hybrid and Regenerative treatments were strip-tilled, while the Conventional treatment was fully cultivated. The Regenerative treatment received the most biological and foliar applications, the Hybrid treatment received some, and the Conventional treatment received none. The Regenerative treatment also received significantly less nitrogen (18 kg N/ha) compared with the Conventional treatment (77 kg N/ha) and the Hybrid treatment (67 kg N/ha).

The Conventional treatment yielded 52.74 T/ha, the Hybrid treatment yielded 52.00 T/ha, and the regenerative treatment yielded 49.44 T/ha. While these yields look slightly different, there is no significant difference in yield between the treatments (P>0.05). Our highest and lowest yielding sub-plots were both in the regenerative treatment!

We will discuss these findings at the LandWISE Conference: Soil Health for Profit in May.

Conference information and registration is available on our website.

The butternuts in the Carbon Positive trial were planted on the 15th of November. Before the butternuts emerged, there was a high weed pressure in the conventional treatment. Therefore, it was sprayed with Buster, while the other two treatments were not.

Emergence

When the butternuts started to emerge, we noticed there was cutworm damage and found cutworms. Cutworms are one of the main insect pests in butternut crops. They chew through the butternut’s stem at ground level, killing the plant. Once we identified the problem, we sprayed Bestseller before the cutworms did too much damage.

Side Dressing

Before sidedressing, our fortnightly soil nitrate testing showed there was 80 kg N/ha in the Conventional treatment, 71 kg N/ha in the Hybrid, and 62 kg N/ha in the Regenerative treatment.

At sidedressing, the Conventional treatment received the ‘standard’ rate of YaraBela CAN (150 kg/ha). For the Hybrid treatment, the goal was to apply a half rate of YaraBela CAN (75 kg/ha), but the lowest the side dressing machine could be calibrated to was 113 kg/ha, so that is the rate we used. The Hybrid treatment also received a foliar application of seaweed. The Regenerative treatment only received a foliar application of seaweed, Megafol, and fulvic acid, as the soil nitrate results showed there was a sufficient level of Nitrate-N in the soil.

Weed Management

Standard weed management would use an inter-row cultivator before the butternuts start running. We felt there wasn’t a high enough weed pressure to do this, and that it could cause a weed strike if we disturb the uncultivated areas in the Hybrid and Regenerative treatments. All treatments were hand-weeded with a push hoe to remove any weeds before the butternuts started to run.

Operation Advisory Group

The Operation Avisory Group has met weekly, and they are happy with how the butternuts are growing, the low weed pressure and the disease pressure.

A big thank you to Andy for taking the time to side-dress our butternuts.

Carbon Positive is a partnership between LandWISE, the HB Future Farming Trust, McCain Foods, Heinz-Wattie’s and Process Vegetables NZ.

During the tomato crop (26/10/2023 – 6/3/2024), the Regenerative treatment had significantly lower nitrate levels than the Conventional and Hybrid treatments, despite all three receiving similar amounts of nitrogen. This lower nitrate level was likely due to the breakdown of the cover crop. Approximately 12 t/ha of cover crop, mainly oats, was incorporated into the soil two days before planting, which would have tied up nitrogen.

Since then, different amounts of nitrogen have been applied across treatments, and there has been no significant difference in soil nitrate levels, except during the period when the Conventional and Hybrid treatments were in peas, while the Regenerative treatment remained in cover crop.

Amount of Nitrogen applied during each crop, by treatment.

Butternuts

Our pre-season soil tests showed that there was 110 kg of potentially available nitrogen in the Conventional, 93. 3 in the Hybrid and 97.3 in the Regenerative treatment.

Two days before the butternuts were planted, there were 32 kg Nitrate-N/ha in the Conventional, 39 in the Hybrid, and 46 in the Regenerative treatment.

At planting, the Conventional and Hybrid treatments received 300 kg of Complex, whereas the Regenerative treatment received 150 kg of Complex. This increased the kg of Nitrate-N in the Conventional to 80, the Hybrid to 71, and the Regenerative to 63.

At side dressing, the Conventional treatment got 150 kg/ha of CAN. The Hybrid got 113 kg/ha of CAN and a foliar application of seaweed. The Regenerative treatment got a foliar application of seaweed, Megafol, and fulvic acid.

When testing for nitrate after side dressing, we avoided the area where the fertiliser was applied. The nitrate test showed similar results to last time. There is 74 Kg of Nitrate-N in the Conventional, 73 in the Hybrid and 65 in the Regenerative treatment. We can assume the conventional is 18 kg higher and the Hybrid is 13.6 kg higher, as this is how much nitrogen was applied at side dressing.

Our aim is to push the limits of regenerative cropping to understand how much nitrogen input can be reduced. Based on potentially available nitrogen and fortnightly soil nitrate results, the Operations Advisory Group decided not to apply granular fertiliser to the Regenerative treatment at side-dressing.

A similar approach was taken last season in beans, where no granular fertiliser was applied at side-dressing and a foliar approach was used instead. Soil nitrate levels remained similar across all treatments, and the Regenerative treatment produced the highest bean yield.

We will continue to monitor nitrate levels fortnightly, and we will do leaf testing during fruit set.

The Conventional treatment was planted with treated seed and 300kg/ha of Complex fertiliser.

The Hybrid treatment was planted with treated seed, coated in TrichoStart and 300kg/ha of Complex fertiliser. Mycorrcin, Biostart N and TrichoStart were applied at planting via liquid injection.

The Regenerative treatment was planted with untreated seed, and 5kg/ha of humates mixed with 150kg of Complex fertiliser. As with the hybrid treatment, mycorrcin, Biostart N, and TrichoStart were applied via liquid injection.

After planting, all treatments received Ironmax slug bait before two 50cm strips of pre-emergeence herbicide, Frontier-P and Magister, were strip-sprayed over the plant lines.

Throughout the season, the Operations Advisory Group and Heinz-Wattie’s agronomists will meet weekly to track how the butternuts are growing. Together, they’ll make the calls on crop protection, weeding, fungicide and insecticide use, and adjust management decisions as the season unfolds.

A big thank you to Gareth Holder from Redloh Horticulture for taking the time to plant our butternuts.

Carbon Positive is a partnership between LandWISE, the HB Future Farming Trust, McCain Foods, Heinz-Wattie’s and Process Vegetables NZ.

There are three scopes within carbon accounting: Scope 1, Scope 2 and Scope 3. Scope 1 is direct GHG emissions from sources controlled or owned by a business.  Scope 2 is indirect GHG emissions from electricity purchased by a business. Scope 3, which is broken down into 15 categories, is all other indirect GHG emissions not controlled or owned by a business.

Carbon accounting calculator

We developed a carbon accounting calculator that quantifies the emissions from the different management systems. We are considering making it into a webtool for others to use.

The Scope 1 emissions we considered were fertiliser use, fuel use, and livestock. The Scope 2 emission was from the power used to run the Irrigator. Scope 3 emissions were from the manufacturing and transportation of fertilisers and agrichemicals.

We set the farm gate as our boundary for crops produced, so we have not calculated transport to the factory (the same for all treatments), food processing, sales or home cooking etc. We have included those factors that make most impact and that are within our control. This parallels the Gross Margin accounting we use to assess profitability of the different treatments in our trial.

Emission factors were used to determine the CO2 equivalent (CO2-e) for each operation within the Carbon Positive trial. An emission factor is a coefficient that converts an activity to a greenhouse gas emission. For example, 1 kilogram of non-urea nitrogen has an emission factor of 4.84 kg CO2-e; therefore, you multiply the amount of fertiliser used by the emission factor to determine total emissions.

• The emission factors for fertiliser, fuel use, livestock, and power were all sourced from the Ministry for the Environment: Te ine tukunga: He tohutohu pakihi Measuring emissions: A guide for organisations.
• The fertiliser manufacturing emission factors were sourced from Wells 2001: Total energy indicators of agricultural sustainability: Dairy farming case study.
• The fertiliser transportation emission factor is an average of different fertilisers being transported to New Zealand, sourced from Ledgard & Falconer 2019: Update of the carbon footprint of fertilisers used in New Zealand.
• The emission factors for agrichemicals manufacturing and transportation were sourced from Audsley et al. (2009): Estimation of the greenhouse gas emissions from agricultural pesticide manufacture and use, with original data from Green (1987). Emission factors for the active ingredients were used if available; otherwise, the average value was used for the agrichemical type: Herbicide, Fungicide, or Insecticide.

Carbon accounting calculator results

Over 2022-2025, the first 3 years of the Carbon Positive trial, the Conventional treatment had the highest emissions (5,906 kg CO2-e). The Hybrid treatment (4,401kg CO2-e) was next, and the Regenerative treatment (3,575 kg CO2-e) was lowest. Nitrogen fertiliser followed by fuel were the highest emission sources in all treatments.

In the first three years, only the conventional plots had sheep grazed on them. The other plots were left in ungrazed cover crops. Over later winter 2025, we did have sheep grazing on all three treatments and they will show up in our next update. Note from the chart above, that sheep had about the same emissions as our agrichemicals.