May 29, 2009

Figure 1. Field trial of skip-row sorghum in wheat residue near Sidney.

Tips for Skip-Row Success Minimize soil water loss by maintaining crop residue cover and good weed control following the previous crop and throughout the crop season. Fertilize according to your yield goal. Apply nitrogen pre-plant to avoid having too little rainfall to move nitrogen into the root zone. Plant at the same seed rate per acre as when planting all rows. This means increasing the within row plant density by 100%, or by 50% with plant 1 - skip 1.

Skip-Row Corn Research Bob Klein, Extension western Nebraska crops specialist, reported on skip-row planting of corn in a January 2009 article, Skip-Row Corn Provides Improved Drought Tolerance. Research was also conducted at 11 site-years for sorghum.

Skip-row planting involves leaving some rows unplanted. Common skip-row configurations are planting alternate rows (plant 1 – skip 1) or alternate pairs of rows (plant 2 – skip 2), or planting two rows and skipping one row (Figure 1). Skip-row planting is a means of saving soil water for the reproductive stages of growth because the roots do not reach the soil water under the unplanted row areas until well into July.

Sorghum Skip-Row Field Trials

In 10 trials where skip 1 - plant 1 and skip 2 - plant 2 were compared to all rows planted, skip-row planting of sorghum resulted in higher grain yield when grain yield was constrained by inadequate rainfall to 70 bu/ac or less. At higher yields, yield was less with skip-row planting. Panicle emergence and pollination are often delayed with soil water deficits. This was observed at three sites in 2005 where pollination was 10-12 days later with all rows planted compared to skip-row planting. Such delays increase the risk of killing frost before the grain is mature. Also, tillering decreased and panicle maturity was more uniform with skip-row planting.

We did not use the plant 2 - skip 1 planting pattern in these trials, but I would expect it to have more yield potential under less severe water deficits than the other skip row treatments. We do not have enough data to determine at what yield point this skip-row pattern has an advantage over all rows planted. In a 2008 trial near Curtis, the mean sorghum yield was 121 bu/ac with all rows planted and 108 bu/ac with plant 2 - skip 1. We are conducting more trials with plant 2 - skip 1 rows in 2009. 

Conditions Favoring Skip-row Planting

• A good ground cover of residue will minimize evaporative losses. Best results are expected with no-till, especially when the previous crop was winter wheat. Cut wheat to maximize stubble height, spreading the straw and chaff evenly over the soil. Minimizing traffic to leave more standing stubble will also help reduce evaporative losses.
• A soil with good water-holding capacity, such as a deep loam, silt loam, or silty clay loam
• Frequent soil water deficits during the reproductive stages

Disadvantages of Skip-Row Planting

• When there's sufficient rainfall, the skip-row pattern may not outyield all rows planted. For example, when the yield with all rows planted is 160 bu/ac, the yield with plant 1 – skip 1 is likely to be around 130 bu/ac. The equation relating yield with plant 1 - skip 1 (YP1:S1) to yield with all rows planted (YS0) is: YP1:S1 = 25 + 0.66 YS0.
• Weed control is likely to be more difficult.
• Crop insurance may not be available or only partially available.
• The Farm Service Agency may not count all acres as planted acres. Check with your FSA office.

Charles Wortmann
Extension Soils Specialist