One approach to achieving high nitrogen (N) use efficiencies in crop production is to accurately estimate site‐specific non‐fertilizer N sources, including N mineralization from soil organic matter (SOM). In the present study, an N balance method was used to determine N mineralization during the growing season in 24 conventional annual cropping fields between 2021 and 2023 in northern and central California. This study included five soil orders (Alfisols, Entisols, Histosols, Inceptisols, and Mollisols), three crop types (corn, sunflower, and spring wheat), and SOM contents ranging from 1.2% to 44% and clay contents from 22% to 65%. By considering all sources and sinks of N over the growing season, apparent net N mineralization was calculated for the top 120 cm of the soil profile. Apparent daily net N mineralization during the growing season averaged 0.94 kg N ha ⁻¹ day ⁻¹ in the top 120 cm of soils with a low SOM content (less than 3%) and 2.41 kg N ha ⁻¹ day ⁻¹ in soils with a high SOM content (5.7%–44%). The proportion of total soil N mineralized decreased with increasing clay content in soils with a low SOM content and decreased with increasing total soil N in soils with a high SOM content. The results of this study allow for site‐specific estimates of N mineralization from SOM, which can be incorporated into N budgets to determine N fertilizer needs. The variability in the dataset underscores the importance of combining N budgets with N monitoring tools, such as soil or plant tissue sampling, prior to in‐season N applications. These practices allow for making corrections to the N fertilizer program when needed, optimizing yield while minimizing N losses.

Sorghum cultivars, particularly those used for forage and biomass, present significant potential as drought-resistant crops suitable for animal feed and biofuel production. This study evaluated 59 sorghum hybrids over five years (2019–2023) across three University of California research farm locations in the Central Valley: Kearney REC (KARE), West Side REC (WSREC), and Davis. The primary aim was to identify genotypes that exhibit high yield and stability across diverse environments in California, which is crucial for meeting the state’s significant feed needs associated with dairy operations and animal production. The evaluation focused on biomass yields, forage quality traits such as Relative Feed Quality (RFQ) and milk yield per ton (milk/ton), and biofuel-relevant chemical compositions like Neutral Detergent Fiber (NDF) and starch. A multi-trait stability index was employed to pinpoint superior genotypes that combine high yield with desirable quality traits. Results indicated significant genotypic, environmental, and genotype-by-environment (GxE) interaction effects for all traits except fat and water-soluble sugars. Eight hybrids were notable for maintaining high and stable biomass yields across different locations. Additionally, high fat and starch content were found to correlate with improved milk/ton potential, while lower fiber content (ADF, NDF) was associated with enhanced RFQ. Specifically, nine hybrids were identified as optimal for dairy forage due to their combination of high yield, RFQ, and milk/ton. Furthermore, distinct hybrids were identified for first-generation (starch-based) and second-generation (NDF-based) biofuel strategies. Three hybrids stood out as having desirable traits for both feed and biofuel applications, underscoring their versatility. This study highlights the utility of a multi-trait stability index in selecting superior sorghum genotypes for specific trait combinations. The identified candidates for forage and biofuel use, especially the multipurpose varieties, offer valuable insights that can aid growers and industry stakeholders in developing more sustainable and versatile sorghum production systems in California. Findings from this study contribute significantly to the development of more resilient sorghum production systems. By identifying hybrids that excel in both yield and quality across various environments, this research supports future cropping decisions aimed at enhancing water use efficiency and drought resilience in sorghum cultivation. These advancements are crucial for maintaining competitive dairy operations and advancing biofuel production in the face of climate change-induced challenges.

Agronomic cropping systems in many regions face growing economic and management challenges as well as new regulations designed to address negative environmental and social externalities. At the same time, public support for agricultural education and extension is decreasing. Hence, new approaches are necessary to understand the most pressing on‐farm issues and help prioritize critical needs. With a diversity of agronomic crops and new regulations for water and nitrogen, California is an important case study for other regions. The objective of this study was to identify major grower and industry concerns, management challenges, and motivations in making management decisions. In 2020, 483 growers, consultants, and allied industry of agronomic crop production responded to an online survey. The crops most widely grown by respondents included rice (Oryza sativa L.), alfalfa (Medicago sativa L.), wheat (Triticum aestivum L.), and corn (Zea mays L.). Four out of the five top concerns were related to water. Weed control and irrigation/water management were primary management challenges, though differences occurred by crop and region. The highest priorities considered in grower management decision‐making were water, profitability, and land stewardship. Crop rotation benefits were a primary reason for growing agronomic crops, with profitability and tradition ranking closely behind. This study highlights opportunities to guide research and extension efforts based on critical needs identified by growers and industry, while also informing larger policy and institutional decisions regarding new programs and funding to address key issues in agronomic crop production.

In both April 2018 and September 2019, cowpeas / black-eyed peas (Vigna unguiculata) in one field in Tulare County, California were observed with tap root rot, both underground (foot) and aboveground stem rot, and in some cases canopy decline, compromising bean formation. In both fields, < 5% of plants appeared affected. Foot and stem segments (~1 cm) of 5-10 plants / field were disinfested sequentially with 0.1% Tween 20 (dip), 70% ethanol for 30 s, and 1% sodium hypochlorite for 2 min and placed on 1:10 potato dextrose agar with 0.03% tetracycline and Fusarium selective medium (Leslie and Summerell 2006). Fusarium-like isolates (dominant in isolation plates) were transferred to 0.6% KCl agar, where fusiform, curved macroconidia and varied microconidia in false heads on elongated monophialides were observed, characteristic of the Fusarium solani species complex (FSSC) (Leslie and Summerell 2006). Isolates CS221, CS222, and CS520 (representing different plants and locations) were saved as single hyphal tip cultures. An Illumina-derived genome sequence was assembled (Burkhardt et al. 2019) and partial tef1ɑ and rpb2 sequences (O'Donnell et al. 2022) were extracted from genome sequences in silico. Sequences were 99.9-100% identical to one another and to deposited F. falciforme isolates based on Fusarium ID and Fusarium MLST for tef1ɑ and rpb2, respectively (tef1a accessions: NRRL 28562 and NRRL 32331; rpb2 accession: NRRL 22857), and were deposited in GenBank (accessions in supplementary table). Pathogenicity was evaluated in three-week-old cowpea plants (cv. CB46rk2) in the greenhouse (13.5-33.6℃; 12:12 h L:D). The tap root / stem was wounded (1 mm wide, 2 mm deep) ~ 2 cm below the soil line and drenched with 50 ml of 106 spores / ml 0.1% water agar or with 0.1% water agar (negative control). The trial was arranged in a Randomized Complete Block Design with three blocks and 2-3 plants / isolate / block, and conducted twice. 52 d post-inoculation, below ground tap root / stem rot developed in 83% of F. falciforme-inoculated plants, with lesion lengths ranging from 25.2 ± 4.2 to 29.2 ± 8.0 mm (P = 0.893 for isolate, ANOVA). Canopy decline developed in 33-50% of plants across treatments in trial 1 (P = 0.859 for isolate) but not in trial 2, likely due to cooler conditions in trial 2 (January-March) vs. trial 1 (May-July), which were less stressful. F. falciforme isolates did not affect bean biomass (dry weight) vs. negative controls (12.5-14.8g / plant; P = 0.949 for pathogen treatment). FSSC isolates were recovered from 100% of symptomatic plants in the inoculated treatments but not in negative controls (both trials) and representative isolates from all treatments were confirmed as F. falciforme (tef1a analysis; trial 2 only). This study establishes F. falciforme as a root and stem rot pathogen of cowpea in California-a disease previously attributed to the morphologically and phylogenetically distinct F. phaseoli (syn. F. solani f. sp. phaseoli), but which lacked modern etiological studies (Frate et al. 2018; Geiser et al. 2021). This work is consistent with previous reports of F. falciforme as a root / stem rot pathogen in cowpea (Ajamu et al. 2023) and other beans (Sousa et al. 2017; Duarte et al. 2019). Clarification of disease etiology will improve accurate diagnosis and effective crop rotation-based management, since F. falciforme is also a pathogen of other California crops including melon, tomato and pistachio.

Agronomic crop production in California, including grains and animal feed, faces multiple challenges that could be addressed by extension support. This means that extension services need to understand priorities for using their limited resources. Until now, a statewide assessment of the most important topics for research and extension was lacking. A survey was conducted by the University of California Cooperative Extension (UCCE) to identify high-priority needs and inform extension programming based on grower, consultant, and allied industry input. Our goal was to compare the importance of different topics with the level of satisfaction regarding UCCE’s delivery of information on these topics. Survey respondents identified integrated pest management, nutrient and irrigation management, and variety testing as high-priority needs, with overall high satisfaction regarding UCCE’s program delivery on these topics. Topics needing more focus (high priority but below-average level of satisfaction) included testing new products, soil health management, and water conservation and storage. Areas of low priority and low satisfaction included niche marketing, emerging crops, organic production, harvest/post-harvest technology, salinity management, compost and manure management, and greenhouse gas emission reductions. To address stakeholder challenges, results from this study suggest that research and extension efforts should prioritize issues directly impacting on-farm crop production. At the same time, areas of low interest reflect a need for more support to engage farmers on these topics, particularly those concerning state environmental regulations and challenges to local and global food production and security.

Variability of dairy process wastewater (PWW) nitrogen (PWW‐N) content makes precise fertilizing of forage challenging. Our objective was to improve measurement accuracy of PWW‐N. We characterized PWW‐N and quantified its variability using over 1,000 PWW samples from 91 lagoons on commercial California dairies. We used statistical modeling and stochastic simulations to compare the accuracy of various protocols for measuring PWW‐N applied to forage crops. Electrical conductivity (EC) was positively correlated with N concentration within a lagoon (conditional R² = .69, mixed model). Simulations compared the accuracy of N application rates when lagoon samples for N analyses were collected more frequently and from more homogeneous lagoons. When sampled quarterly, the N application measurement error was ±50%. Homogenizing PWW and sampling weekly reduced measurement error to ±42 and ±30%, respectively. Simulations using EC as an N concentration proxy within an automated irrigation system reduced N application measurement error to ±5%. More accurate automated N concentration measurements allow for precision N management that meets yield goals and reduces environmental effects.