Planting Date Effect on No‐till Proso Millet

Producers in the Central Great Plains are changing their cropping systems to include summer annual crops after winter wheat ( Triticum aestivum L.). Proso millet ( Panicum miliaceum L. —hereafter referred to as proso) is well adapted to this region, especially when planted after winter wheat. This study examined the response of proso to planting date in a no‐till system. ‘Cope’ proso was planted at six weekly intervals, starting on 18 May. Proso yielded highest when planted on 8 June and will yield greater than 95% of its potential if planted between 2 June and 12 June. Water use efficiency (WUE) reflected grain yield trends, with WUE highest when proso was planted in early June. Total crop water use (soil water + growing season precipitation) ranged between 13 and 14 in. for all planting dates. Proso initiated stem elongation and anthesis after approximately 600 and 1100 growing degree days, respectively, regardless of planting date. Based on this study, producers should plant proso during early June to maximize yield potential in no‐till systems. Research Question Winter wheat‐fallow is the most common rotation in the Central Great Plains. Because of improved weed control during noncrop periods, producers are now cropping more intensively with less fallow. Proso millet is well adapted to this region and commonly grown after winter wheat. Producers traditionally sweep plow their fields after wheat harvest for weed control, then disk in the spring to prepare a seedbed. To meet current government program requirements, however, producers must minimize tillage to maintain crop residues on the soil surface. Therefore, many producers are planting proso millet into no‐till wheat stubble. The objective of this research was to examine planting date effect on proso millet grown in a no‐till production system. Literature Summary Optimum planting date for proso millet has been reported for tilled production systems. Highest grain yield occurred when proso millet was planted on 15 May, with yield decreasing at either earlier or later plantings. This response was similar for several varieties. It is well documented that residue on the soil surface slows crop development because it reduces soil temperature in spring. High residue levels delay seedling development of corn, winter wheat, and spring wheat, and in some years, reduce yield. Because plant development is usually delayed by high residue level, one would expect that the optimum planting date for proso millet growth in a no‐till system would differ from a tilled system. Study Description Proso millet was planted on six dates in 1988, 1989, and 1990 at Akron, co. Soil type: Weld silt loam Planting dates: 18 May, 25 May, 1 June, 8 June, 15 June, and 22 June Variety: ‘Cope’ proso millet Planting rate: 10 lb/acre Drill type: Hoe drill with 12 in. row spacing N application: 30 lb N/acre of ammonium nitrate, broadcast Growing season precipitation (June, July, and August): 5.7 in. in 1988, 9.5 in. in 1989, and 10.1 in. in 1990. Location long‐term average: 7.2 in. Agronomic measurements: grain yield, water use efficiency, and crop water use Applied Question What is the optimal planting date for proso millet grown in a no‐till production system? Highest grain yield occurred when proso millet was planted on 8 June, with yields decreasing at earlier and later plantings (Fig. ). Yield decreased by 20% when planted on 18 May and 22% when planted on 22 June compared with the 8 June planting. The optimum proso millet planting date in a no‐till system is approximmately 3 wk later than for a tilled system. Producers will achieve within 5% of maximum grain yield by planting between 2 June and 12 June. Crop water use efficiency response to planting date was similar to grain yield. When planted on 8 June, proso millet produced 260 lb grain/acre per inch, with water use efficiency declining with earlier and later plantings, decreasing by 18% when planted on 22 June and 20% when planted 18 May. Crop water use ranged between 13 and 14 in. for all planting dates. Proso millet grain yield at six planting dates. Data are averaged over all years of study. image