Double-Cropping and Crop Rotation Effects on Diseases and Grain Yield of Pearl Millet

Abstract

The effects of double-cropping and crop rotation sequences on grain yield and diseases of pearl millet [Pennisetum glaucum (L.) R. Br] were evaluated to determine the compatibility of pearl millet in southeastern agricultural cropping systems. Pearl millet hybrid ‘HGM 100’ (AgraTech Seeds, Inc., Atlanta, GA) was planted with minimum tillage, double-cropped with canola (Brassica napus L.) and wheat (Triticum aestivum L.). Soybean [Glycine max (L.) Merr.] was used as an alternative summer annual to pearl millet in rotation sequences. Treatment effects on seedling stand density, panicle number, grain yield, leaf blight (caused by Exserohilum rostratum), stalk and neck rot (associated with a number of fungi), and smut (caused by Moesziomyces penicillariae) severity were determined. Seedling stands 3 wk after planting were lower following canola than wheat in 1995 and 1997, and panicle number was lower in 1997. No other yield-associated variables were affected by the previous winter crop. In comparison of crop rotations, inconsistent effects were observed in stand density in 1997, and panicle number in 1996 and 1997. Seedling stand density and panicle number were lower with 2 yr of pearl millet compared with 1 yr, but were highest for the 3 sequential yr of cultivation in 1997. A trend toward increased smut severity in plots continuously planted to pearl millet was observed in 1997. Within subplots, stand density was highly correlated with panicle number in 1996 and 1997 (r e 0.51, P < 0.01), with leaf blight severity in 1995 and 1996 (r d0.33, P < 0.01) and with stalk and neck rot in 1996 (r = 0.60, P < 0.01). Yield was negatively correlated (r ≤ −0.31, P < 0.01) with leaf blight severity in 1995 and 1996, and stalk and neck rot in 1996 (r = −0.46, P < 0.01). Stalk and neck rot in 1996 was probably caused by Fusarium graminearum, which was more commonly isolated from pearl millet following canola than wheat. Neither the previous winter annual crop nor the number of sequential years of pearl millet cultivation had detrimental, limiting effects on pearl millet grain yield or diseases. Introducing alternative crops into established production systems requires crops to be culturally and biologically compatible in double-cropping and crop rotation sequences. Pearl millet is an alternative high-quality feed grain for poultry (Adeola et al., 1994; Kumar et al., 1991; Savage, 1995; Amato and Forrester, 1995) but grain supplies are limited. Grain hybrids adapted to the southeastern USA have a short growing season and can be planted over a period of several months, thus, they are culturally compatible with most winter annual crops. Very little information is available concerning the biological compatibility of different winter annual crops which might affect pearl millet grain yield and diseases. Research Question Introduction of alternative crops into established production systems requires crops to be culturally and biologically compatible in double-cropping and rotational sequences, with beneficial or neutral effects on soil quality, severity of soil borne diseases, and yield. Pearl millet grain hybrids adapted to the southeastern USA have a short growing season, therefore, they are culturally compatible with most winter annual crops. Limited information is available concerning the biological compatibility of different winter annual crops on pearl millet grain yield and diseases, and management information for pearl millet grain production in the USA is vitally needed. Profitable production of this crop will require knowledge of beneficial or detrimental effects in double-cropping and rotation sequences. The objectives of these studies were to assess yield and diseases of pearl millet double-cropped with either wheat or canola and rotated with soybean. Literature Summary Few cropping sequences were shown to affect pearl millet yield. Pearl millet can be successfully grown following soybean with no additional N applications. Grain yields are improved in rotations with legumes in arid, sandy soils, probably as a result of improved soil properties, and yield responses usually occur only in seasons with well distributed rainfall. Soil properties, fertility, soil tillage, water availability, and to a lesser extent, proper seeding rates all contribute to enhance grain yield. Study Description In a 3-yr experiment, pearl millet hybrid ‘HGM 100’ was planted after minimum tillage in double-cropping sequences with wheat or canola, and in rotational sequences with soybean. Seedling stand density, panicle counts, leaf blight severity, stalk and neck rot incidence, fungi associated with stalk rot, smut severities, and yield were determined. Applied Questions Does double-cropping with wheat or canola or rotation with soybeans affect pearl millet diseases or grain yield? Pearl millet stands were reduced following canola in 1995 and 1997. The reduced stand density resulted in lower panicle numbers only in 1997. Grain yield, leaf blight severity, and stalk and neck rot were not affected by the previous winter crop or the number of years of pearl millet cultivation. Smut severity increased after 3 sequential yr of pearl millet. Over all treatments, seedling stand density was correlated with panicle number, leaf blight severity, and stalk and neck rot incidence. Grain yield was negatively correlated with leaf blight severity and stalk rot incidence. Are fungi associated with stalk rot affected by double-cropping and rotation? Fusarium semitectum, F moniliforme, F graminearum, Alternaria spp, Nigrospora spp., Bipolaris setariae, and F. equiseti were most frequently isolated and each comprised at least 5% of the isolates from diseased stalks. These fungi exhibited distinct distributions within pearl millet stalks. F. semitectum was isolated from pearl millet more frequently following canola than wheat, and from pearl millet following soybean than pearl millet. The influence of canola and soybean on soil populations of Fusarium species is unclear. F semitectum is an important component of the grain-mold complex of pearl millet and increased isolation from stalks suggests a greater inoculum potential exists with increased potential for grain molds in pearl millet following canola than wheat.