No abstract

No abstract

No abstract

No abstract

Crop over‐fertilization has economic and environmental consequences. Sugarbeet (Beta vulgaris L.) N fertilizer requirements could be lower than expected when planted after shallow rooted onion (Allium cepa L.). Sugarbeet was planted on an Owyhee silt loam (coarse‐silty, mixed, mesic Xerollic Durorthid) for 2 yr, where the previous onion crop had received 0, 60, 120, 240, and 480 kg N ha−1. Soil nitrate and ammonium were measured in 0.3‐m increments to 1.8 m deep after harvesting onion, and before and after growing sugarbeet. Nitrogen uptake by plant parts, and beet and sucrose yields, were measured. Averaged across years, sugarbeet recovered 336, 316, 338, 400, and 505 kg N ha−1 when N fertilizer of the previous onion crop was 0, 60, 120, 240, and 480 kg ha−1, respectively. The corresponding reduction in available inorganic N from the top 1.8 m of the soil during sugarbeet growth was 27, 82, 62, 120, and 152 kg ha−1. Nitrogen recovered by sugarbeet was largely supplied by sources other than preplant available N. Recovered sucrose yield was near maximum when the N rate on the previous onion crop was 240 kg ha−1, which resulted in preplant NO3–N levels of about 70 kg ha−1 in the top 0.6 m of the soil. Sucrose yield did not improve when petiole NO3–N in late June exceeded 6 g kg−1. In conclusion, sugarbeet may not require fertilizer N when grown after onion fertilized with about 240 kg N ha−1

Granular matrix sensors (GMS) represent an alternative technology for measuring soil water to schedule irrigation. When GMS were tested by drying them to measure changes in electrical resistance with decreasing water content, their resistance response to drying in air in an oven was similar (t = −0.87, 134 df) to that for drying in a field soil, with a response curve that suggested GMS could be used to measure soil water potential (Ψ). Granular matrix sensor meter readings were compared with tensiometer, neutron probe, and gravimetric measurements of soil water in the root zone of potato (Solanum tuberosum L. cv. Russet Burbank) grown in silt loam. Measurements with GMS were closely related to soil water potential measurements and to soil water measured gravimetrically or by neutron probe. Meter model 30KTC, as supplied by the manufacturer, when calibrated against tensiometers, had a linear response represented by the equation y = −6.44 − 0.738 x, where y = Ψ J kg−1), and x = 30KTC meter reading (dimensionless units) of GMS, with r2 = 0.89. Granular matrix sensors were used to monitor transitory soil water stress treatments in an experiment to determine potato response to water stress.

Portable plot sprinklers were developed that allowed individual plots to be irrigated independently of other plots. Each plot sprinkler consisted of three rotary‐pendulum, square‐pattern sprinkler heads mounted on a PVC pipe frame. Plot sprinkler water output was 0.9 m3 h−l, on an area 4.6 m wide by 13.7 m long, with Cu = 80%, when operated at 86 kPa. Plot sprinklers were used to apply irrigation treatments In a randomized block design to evaluate potato (Solanum tuberosum L. ‘Russet Burbank’) tuber quality response to six levels of transitory drought stress during early tuber bulking. Yield of U.S. Number One tubers decreased and yield of U.S. Number Two tubers increased with increasing severity of transitory drought stress. Plot sprinklers allow irrigation of plots in an experiment at different frequencies or durations.

There is widespread concern about loss of sediments, NO‐3, and phosphate into surface water from irrigated farmlands. We studied the effects of 900 kg ha−1 wheat (Triticum spp.) straw, mechanically applied to irrigation furrows, on sediments and on N and P losses in the runoff. The field was on a Nyssa silt loam soil (coarse‐silty, mixed, mesic Xerollic Haplodurid) with 3% slope planted to onion (Allium cepa L.), and received 0, 50, or 200 kg P ha−1 incorporated to 0.1 m deep. Furrows were side‐dressed with 200 kg ha−1 N. Averaged across 17 irrigations, straw reduced runoff volume by 43%. Cumulative sediment lost after 17 irrigations was 17 Mg ha−1 for mulched and 333 Mg ha−1 for unmulched furrows. Straw also reduced NO‐3 and NH+4 losses in runoff solution and sediments. Total N losses during the first 6 irrigations were 33 kg ha−1 from mulched and 230 kg ha−1 from unmulched furrows. Straw effect on N loss was only through changes in the runoff volume and sediment loss. In contrast, as fertilizer P increased, PO4 concentrations in runoff solution and sediments also increased. Averaged across the first 6 irrigations, straw mulch reduced PO4 losses in the runoff solution by 59, 61, and 72%, for the 0, 50, and 200 kg P ha−1 treatments, respectively. Straw reduced PO4 losses in the sediment 15‐, 11‐, and 15‐fold for the 0, 50, and 200 kg P ha−1 treatments, respectively. Averaged across P fertilizer rates, total P lost after 6 irrigations was 18 kg ha−1 from mulched and 215 kg ha−1 from unmulched furrows. Mechanically applied straw mulch in irrigation furrows can substantially reduce soil erosion and N and P losses to surface water runoff.