Extending Cover Crop Benefits with Zone Till Management in Northern Organic Summer Squash Production

Peyton Ginakes,Julie M Grossman

doi:10.3390/agronomy11050983

Abstract

Winter annual legume cover crops often fail to reach full maturity by spring vegetable planting dates in northern climates, which prevents maximum nitrogen (N) contributions. To determine if delayed termination improved cover crop biomass and N content, we evaluated winter rye + hairy vetch (Secale cereale L. + Vicia villosa Roth) and oat + field pea (Avena sativa L. + Pisum sativum L.) cover crop mixtures in 2015 and 2016, and medium red clover (Trifolium pratense L.) in 2016, in zone-tilled organic yellow crookneck squash (Cucurbita pepo var. torticollis Harz). In-row regions where cover crops were terminated in early spring during crop row preparation were compared to between-row regions where termination was delayed until legume maturation in late spring. Soil quality (soil inorganic N, permanganate oxidizable C (POXC), and potentially mineralizable N (PMN)) was also determined for in-row and between-row regions at four time points throughout the growing season. In 2015, winter rye + hairy vetch biomass N more than doubled between early and late termination times, with 120 and 258 kg N ha−1, respectively. Permanganate oxidizable C was not responsive to cover crop systems or tillage, and only slightly decreased over time in 2016. Soil inorganic N and PMN after cover crop termination in 2016 provided evidence of localized soil N cycling responses to cover crop termination in in-row and between-row regions. The extended growing period for cover crops between crop rows in the first several weeks of crop growth had no negative effect on crop yield, and appeared to enhance soil fertility.

Highlights

Cover crops play a major role in crop fertility management by preventing nutrient leaching and runoff [1,2,3], providing carbon-rich additions to soil organic matter [4,5], and biologically fixing nitrogen in the case of legumes (N; [6,7,8,9,10,11])
Soil quality indicators with potential to identify the impact of extended cover crop spring growth between rows include both organic and inorganic pools of soil N and permanganate oxidizable C (POXC)
Delaying RV cover crop termination by one month at least doubled RV biomass N content, while OP biomass N decreased by 32 kg N ha−1, though neither difference between sampling times was significant (Table 2)

Summary

Introduction

Cover crops play a major role in crop fertility management by preventing nutrient leaching and runoff [1,2,3], providing carbon-rich additions to soil organic matter [4,5], and biologically fixing nitrogen in the case of legumes (N; [6,7,8,9,10,11]). Zone tillage has recently risen in popularity as an approach for reducing tillage by tilling only areas directly where crops will be sown, and leaving between-row regions untilled This practice has gained traction due to its capacity to improve soil quality by incorporating cover crop residue where crops will be planted, while maintaining living ground cover between rows to prevent. To measure the fraction of soil organic carbon that is accessible to microbes for co-metabolizing with organic N, Weil et al [24] developed a method using potassium permanganate, a strong oxidizing agent, to simulate microbial C oxidation. These assays provide useful insights into nutrient cycling dynamics

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Conclusion