Organic matter amendments improve soil fertility in almond orchards of contrasting soil texture

Yocelyn B Villa,Rebecca Ryals,Stephen C Hart,Sat Darshan S Khalsa,Patrick H Brown,Roger A Duncan

doi:10.1007/s10705-021-10154-5

Abstract

The effects of organic matter amendments (OMA) on soil fertility in permanent cropping systems like orchards is under-studied compared to annual cropping systems. We evaluated experimentally the impact of OMAs on soil fertility in almond (Prunus dulcis) orchards over a two-year period with annual applications. Two OMAs, derived from composted green waste (GWC) or composted manure wood chips (MWC), were applied as surface mulch and compared to a control at two sites with different soil textures (sandy loam and loamy sand). OMAs increased soil moisture content (0–0.1 m depth) at both sites by 27–37%. Both amendments increased soil inorganic N at the sandy loam (GWC: 194%; MWC: 114%) and loamy sand (GWC: 277%; MWC: 114%) sites the month following application, but soil inorganic N concentrations quickly decreased to values similar to those of control plots. After two-years, the GWC and the MWC amendments increased the soil cation exchange capacity (CEC) by 112% and 29%, respectively, in the sandy loam site, but no change was observed in the loamy sand site. The greatest increase in soil extractable K occurred in the GWC-amended plots at the sandy loam site even though the initial K concentration of MWC was higher. Both OMAs increased soil organic carbon (SOC) after two years, but the SOC increase in the GWC-amended plots was greater. Our results suggest that OMAs can significantly improve soil fertility after one or two annual applications, and that fertility gains appear to be dependent on soil texture than the nutrient concentrations of the OMA.

Highlights

Abundant sources of organic matter in the Central Valley, such as green wastes from agriculture and urban areas and manures from dairy production, can help augment soil organic matter (SOM) levels in permanent crops like almond orchards (Khalsa and Brown 2017)
Our results suggest that organic matter amendments (OMA) can significantly improve soil fertility after one or two annual applications, and that fertility gains appear to be dependent on soil texture than the nutrient concentrations of the OMA
We found no significant interaction between OMA type and site (p [ 0.640)

Summary

Introduction

Abundant sources of organic matter in the Central Valley, such as green wastes from agriculture and urban areas and manures from dairy production, can help augment soil organic matter (SOM) levels in permanent crops like almond orchards (Khalsa and Brown 2017). SOM levels in California’s Central Valley soils range from 0.5 to 2.5% (Warren 1996). Permanent crops like almonds planted on 562,525 ha are a prime candidate for the application of organic matter amendments (OMAs). In this region, 82% of the world’s almonds are produced (Almond Almanac 2018). A poor understanding of how to manage OMAs in orchards limits their use and weakens the potential for improvement in soil fertility in these agroecosystems (Khalsa and Brown 2017). Understanding how surficial applications of OMAs influence nutrient dynamics in the short-term in permanent cropping systems poses different challenges than in annual cropping systems where OMAs are incorporated directly into the soil (Jackson et al 2003)

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Discussion

Conclusion