**Section 2**

**Crop Production** 

22 Agricultural Science

Sang, T., D.J. Crawford and T.F. Stuessy (1997) Chloroplast DNA phylogeny, reticulate evolution, and biogeography of Paeonia (Paeoniaceae). Am. J. Bot. 84: 1120–1136. Sheela, V.L., P.R.Geetha Lekshmi, C.S.Jayachandran Nair and K.Rajmohan (2006) Molecular characterization of *Heliconia* by RAPD assay. J. Tropi. Agric. 44: 37–41. Sousa, L.O.F., T.Wendt, G.K.Brown, D.E.Tuthill and T.M.Evans (2007) Monophyly and

morphology and chloroplast dna sequences. Sys. Botany. 32: 264–270. White, T.J., T.Bruns, S.Lee and J.Taylor (1990) Amplification and direct sequencing of fungal

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phylogenetic relationships in *Lymania* (Bromeliaceae: Bromelioideae) based on

ribosomal RNA genes for phylogenetics. *In*: Innis, M., D.Gelfand, J.Sninsky and T.White (eds.). PCR Protocols: A Guide to methods and applications. Academic

**3** 

*USA* 

H. Arnold Bruns

**Concepts in Crop Rotations** 

*Crop Production Systems Research Unit, Stoneville, MS,* 

Crop rotation is the production of different economically important plant species in recurrent succession on a particular field or group of fields. It is an agricultural practice that has been followed at least since the Middle Ages. During the rule of Charlemagne crop rotation was vital to much of Europe which at that time followed a two-field rotation of seeding one field one year with a crop and leaving another fallow. The following year the fields were reversed (Butt, 2002). Sometime during the Carolingian period the three-field rotation system was introduced. It consisted of planting one field, usually with a winter cereal, a second with a summer annual legume, and leaving a third field fallow. The following year a switch would occur. Sometime during the 17th and /or 18th centuries it was discovered that planting a legume in the field coming out of fallow of the three-field rotation would increase fodder for livestock and improve land quality, which was later found to be due to increased levels of available soil nitrogen (N). During the 16th century Charles Townshend 2nd Viscount Townshend (aka Turnip Townshend) introduced the four-field concept of crop rotation to the Waasland region of England (Ashton, 1948). This system, which consisted of a root crop (turnips (*Brassica rapa* var. rapa)), wheat (*Triticum aestivum* L.), barley (*Hordeum vulgare* L.), and clover (*Trifolium* spp.) followed by fallow. Every third year introduced a fodder crop and grazing crop into the system, allowing livestock production the year-round and thus increased overall agriculture production. Our present day systems of crop rotation have their beginnings traceable to the Norfolk four-year system, developed in Norfolk County England around 1730 (Martin, et al., 1976). This system was similar to that developed by Townshend except barley followed turnips, clover was seeded for the third year and finally wheat on the fourth year. The field would then be

seeded to turnips again with no fallow year being part of the rotation.

In the new world, prior to the arrival of European settlers, the indigenous people in what is now the Northeastern United States, practiced slash-and-burn agriculture combined with fishing, hunting, and gathering (Lyng, 2011). Fields were moved often as the soil would become depleted and despite the tale of Native Americans teaching the European settlers to put a fish into the corn hills at planting, there is little or no evidence of the aboriginal people fertilizing their crops. Maize would be planted in hills using crude wooden hoes with gourds and beans (*Phaseolus* spp. L.) being planting alongside and allowed to climb the

**1. Introduction** 

**1.1 Crop rotations – A historical perspective** 

*USDA-Agricultural Research Service,* 
