Remote Sensing of Perennial Crop Stand Duration and Pre-Crop Identification

Crop sequence history both describes results of on-farm decision-making processes and signals potential environmental impacts across landscapes. Remote sensing classifications for 11 yr in western Oregon identified multi-year production of established perennial crops and successive plantings of annual crops, quantified durations, and defined frequencies of pre- and post-crops for multi-year production periods. Measuring duration of continuous production of specific crops and characterizing crop sequence patterns required: (i) optimizing year-to-year landuse consistency and within-year landuse classification accuracy, (ii) sufficiently detailed landuse classes to capture 99% of all crops grown in the diverse agriculture of this region, and (iii) enough years of data that majorities of fields experienced at least one full cycle of planting new stands of perennial grass seed crops (or successive plantings of specific annual crops), maintaining those fields in production until their eventual termination, and subsequent planting of new crops. Averaged over all possible starting and ending years between 2004 and 2014, continuous production of the same crop on the same field ranged from highs of 2.9, 4.6, 3.7, and 5.9 yr for perennial ryegrass (Lolium perenne L.), orchardgrass (Dactylis glomerata L.), tall fescue [Schedonorus arundinaceus (Schreb.)], and Italian ryegrass [L. perenne L. subsp. multiflorum (Lam.) Husnot] grown for seed to lows of 2.4 and 1.5 yr for clovers grown for seed and cereal grains. With very few exceptions, pre-crop frequencies were stable over the period of the study. Variability in perennial ryegrass and tall fescue stand duration included strong local components in which fields with much longer or shorter than average stand durations were oft en found in close proximity to one another.