Row Orientation and Planting Pattern of Relay Intercropped Soybean and Wheat

Relay intercropping soybean [Glycine max(L.) Merr.] into winter wheat (Triticum aestivum L.) may increase soybean yields compared with doublecropping. Once the soybean crop is established, however, it competes with wheat, which may lead to reductions in soybean plant population and seed yield. A skip‐row planting pattern of wheat has been shown to reduce intercrop competition and increase soybean productivity. Row orientation may also influence soybean seedling survival and seed yield. We conducted research to compare soybean response to the effects of row orientation and planting pattern when relay intercropped into winter wheat. Agripro ‘Victory’ wheat was planted in solid intercropped and skip‐row intercropped patterns near Manhattan and Rossville, KS, in 1988 and 1989. Row orientation was north‐south or east‐west. ‘Resnik’ soybean was intercropped into wheat at late boot. In 1989, wheat yield was 11% greater from north‐south rows than east‐west rows. Planting pattern did not influence wheat yield. Solid wheat stands were detrimental to soybean seedlings. Solid intercropped soybean had 29% stand reductions, and 34% lower yields than skip‐row intercropped soybean. Photosynthetically active radiation from soybean emergence to late milk stage of wheat was from 3 to 63% greater in skip‐row intercropped vs. solid intercropped plots depending upon row direction and time of day. Row direction did not significantly influence soybean yield.Research QuestionRelay intercropping soybean into winter wheat may increase soybean yields compared to doublecropping. Once soybean is established, however, it must compete with wheat for light, moisture, and nutrients. This competition may lead to the suppression or death of the soybean. Planting arrangements may influence competition and result in a more efficient relay intercropping system. The primary objectives of this research were to evaluate the effect of row direction and planting pattern on wheat and intercropped soybean performance.Literature SummaryIntercropping soybean into wheat has produced erratic results. Some studies have reported higher soybean yields in an intercropping system than in a doublecropping system, but in others, yields of intercropped soybean have been substantially reduced because of soybean's inability to compete with wheat.Intercrop competition has been reduced by using a skip‐row planting pattern of the wheat. Soybean can then be planted into these skips. Skip‐rows allow more light to reach the seedling soybean and perhaps reduce competition for nutrients and moisture. Skip‐row patterns usually reduce wheat yields; however, in some studies equal yields have been observed in skip‐row and solid planting patterns.Study DescriptionThis research was conducted for 2 yr at two irrigated locations in north‐east Kansas. Soil at both sites was a silt loam. Wheat was planted in solid intercropped and skip‐row intercropped patterns. Row orientation was north‐south or east‐west. Intercropped wheat plots were planted on 8‐in. centers, except for the skip‐row plots which left a 16 in. space for soybean. Soybean was intercropped into wheat at late boot in 24 in. rows.Applied QuestionDid row orientation or skip‐row planting pattern influence the productivity of soybean or wheat?Skip‐rows did not reduce wheat yield and greatly reduced competition to soybean seedlings. This resulted in greater soybean plant populations, and higher seed yield than observed in the solid planting pattern (Table ). Solid wheat stands were detrimental to soybean seedlings. Based on this and similar studies, we recommend that producers use a skip‐row planting pattern when intercropping soybean into wheat.Wheat responded to the row direction treatment in 1989 by producing 11% greater yields in north‐south vs. east‐west rows (Table ). Row direction did not influence wheat yields the second year. Row direction did not significantly influence intercropped soybean yields in either year. Row direction response has not been consistently reported in the literature, and it would not be appropriate to recommend one row direction over another. Soybean seed yield, and plant populations at wheat harvest in a relay intercropping study, averaged across row direction. Planting pattern Solid Skip‐row Solid Skip‐row Environment intercropped intercropped intercropped intercropped ‐‐‐‐‐‐‐bu/acre‐‐‐‐‐‐‐ ‐‐‐‐‐‐‐plants/ft‐‐‐‐‐‐‐ Rossville, 1989 31.9 60.4 2.1 3.4 Manhattan, 1989 55.8 67.3 1.5 1.8 Rossville, 1989 52.5 61.3 2.2 2.4 Manhattan, 1990 23.8 59.5 1.1 2.1 Wheat yields summarized for a relay intercropping study. Site Row orientation Year Rossville Manhattan North‐south East‐west ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐bu/acre‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 1989 57.3 48.5 55.8 50.0 1990 26.6 61.9 44.1 44.5 Averaged across row direction and planting pattern. Averaged across location and planting pattern.